Mining and Metallurgy Engineering Bor

ISSN 2334-8836 (Štampano izdanje) UDC 622 ISSN 2406-1395 (Online)

3-4/2020

Published by: Mining and Metallurgy Institute Bor

Mining and Metallurgy Engineering Bor

3 - 4/2020

MINING AND METALLURGY INSTITUTE BOR

MINING AND METALLURGY ENGINEERING Editorial Board BOR is a journal based on the rich tradition of Prof. Dr Tajduš Antoni expert and scientific work from the field of mining, The Stanislaw University of Mining and underground and open-pit mining, mineral proce- Metallurgy, Krakow, Poland ssing, geology, mineralogy, petrology, geomecha- Prof. Dr Mevludin Avdić nics, metallurgy, materials, technology, as well as MGCF-University of Tuzla, B&H related fields of science. Since 2001, published Prof. Dr Vladimir Bodarenko twice a year, and since 2011 four times a year. National Mining University, Department of Editor-in-chief Deposit Mining, Ukraine Academic Dr Milenko Ljubojev, Dr Mile Bugarin, Principal Research Fellow Principal Research Fellow Mining and Metallurgy Institute Bor Mining and Metallurgy Institute Bor Dr Miroslav R.Ignjatović, Senior Research Associate Full member of EAS Chamber of Commerce and Industry Serbia E-mail: [email protected] Prof. Dr Vencislav Ivanov Mining Faculty, University of Mining and Geology Phone: +38130/454-109, 435-164 "St. Ivan Rilski" Sofia Bulgaria Editor Dr Ivana Jovanović, Research Associate Vesna Marjanović, B.Eng. Mining and Metallurgy Institute Bor English Translation Academic Prof. Dr Jerzy Kicki Gospodarkl Surowcami Mineralnymi i Energia, Nevenka Vukašinović, prof. Krakow, Poland Technical Editor Dr Dragan Komljenović Suzana Cvetković Hydro-Quebec Research Institute Canada Preprinting Dr Ana Kostov, Principal Research Fellow Mining and Metallurgy Institute Bor Vesna Simić Dr Daniel Kržanović, Research Associate Printed in: Grafomedtrade Bor Mining and Metallurgy Institute Bor Circulation: 200 copies Prof. Dr Nikola Lilić Faculty of Mining and Geology Belgrade Web site Dr Dragan Milanović, Senior Research Associate www.irmbor.co.rs Mining and Metallurgy Institute Bor Journal is financially supported by Prof. Dr Vitomir Milić Technical Faculty Bor The Ministry of Education, Science and Technological Development of the Republic Serbia Dr Aleksandra Milosavljević, Senior Research Associate Mining and Metallurgy Institute Bor Mining and Metallurgy Institute Bor Dr Eldar Pirić ISSN 2334-8836 (Printed edition) Mining Institute Tuzla ISSN 2406-1395 (Online) Prof. Dr Dragoslav Rakić Journal indexing in SCIndex and ISI. Faculty of Mining and Geology Belgrade All rights reserved. Prof. Dr Novica Staletović University of Union - Nikola Tesla, Published by Faculty of Ecol. and Envir. Prot. Mining and Metallurgy Institute Bor Academic Prof. Dr Mladen Stjepanović 19210 Bor, Zeleni bulevar 35 Engineering Academy of Serbia E-mail: [email protected] Dr Biserka Trumić, Principal Research Fellow Phone: +38130/454-110 Mining and Metallurgy Institute Bor

Dr Boško Vuković, Assistant professor Scientific – Technical Cooperation with Mine and Thermal Power Plant Gacko the Engineering Academy of Serbia Prof. Dr Milivoj Vulić University of Ljubljana, Slovenia Prof. Dr Nenad Vušović

Technical Faculty Bor CONTENS SADRŽAJ

Aleksej Milošević, Boško Vuković, Miodrag Čelebić FORMATION ANALYSIS OF MAGLAJCI – MOŠTANICA OPHIOLYTIC ZONES IN THE NORTH OF KOZARA FOR THE USE OF ROCKS IN CONSTRUCTION ...... 1

Nenad Vušović, Milica Vlahović, Milenko Ljubojev, Daniel Kržanović STOCHASTIC MODEL AND GIS SPATIAL ANALYSIS OF THE COAL MINE SUBSIDENCE ...... 9

Uglješa Bugarić, Miloš Tanasijević, Miljan Gomilanović, Andrija Petrović, Miloš Ilić ANALYTICAL DETERMINATION OF THE AVAILABILITY OF A ROTARY EXCAVATOR AS A PART OF COAL MINING SYSTEM - CASE STUDY: ROTARY EXCAVATOR SchRs 800.15/1.5 OF THE DRMNO OPEN PIT ...... 25

Nenad Vušović, Milica Vlahović PREDICTION OF SURFACE SUBSIDENCE AND DEFORMATIONS DUE TO THE UNDERGROUND COAL MINING ...... 37

Miloš Ilić, Sandra Milutinović, Branislav Rajković, Daniela Urošević SELECTION OF A DEDUSTING SYSTEM FOR THE LIME STONE PREPARATION PLANT IN THE DEPOSIT "ZAGRADJE - 5" ...... 57

Dejan Bugarin, Ivan Jelić, Miljan Gomilanović, Aleksandar Doderović APPLICATION OF THE COMFAR III SOFTWARE PACKAGE IN DEVELOPMENT A FEASIBILITY STUDY OF INVESTMENT ON AN EXAMPLE OF TECHNICAL-CONSTRUCTION STONE OF THE OPEN PIT GELJA LJUT ...... 67

Nemanja Matić, Boris Siljković, Marko Savić POTENTIALS OF TRADITIONAL CASH METAL COINS VERSUS DIGITAL CONTACTLESS PAYMENT IN THE TIME OF CORONAVIRUS PANDEMIC ...... 81

MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 552.3(045)=111 DOI: 10.5937/mmeb2004 001M

Aleksej Milošević*, Boško Vuković**, Miodrag Čelebić*

FORMATION ANALYSIS OF MAGLAJCI – MOŠTANICA OPHIOLYTIC ZONES IN THE NORTH OF KOZARA FOR THE USE OF ROCKS IN CONSTRUCTION

Abstract

Based on the field work and laboratory research, the basic geological characteristics of the ophiolitic melange of northern Kozara are presented, with an emphasis on the Maglajci ophiolitic block. Crite- ria for separations of formations were established and then applied in the analysis, especially those geologically directly recognizable in the field and outcrops, so one ore formation with two ore subformations was separated in the Maglajci block. In the central zone of block, the basalt outflows and diabase are dominant, while in the south of the block it is an outflow basaltic sequence of the ocean floor with the acidic differences of rhyolites and keratophyres. The second subformation also includes the Moštanica and Vojkova Bloc as a whole. The ore bearing formation is evaluated as a medium to low perspective formation, while parts of the Maglajci block with a massive to brecciated outflow are highly perspective terrain. There are rocks of good physical-mechanical characteristics and they meet the most requesting standards for road building. The results of formation analysis have denied a prior prognosis of ore bearing characteristics of this area, because it was thought that the ophiolitic blocks was built almost exclusively of diabase, and that the fields with those blocks are equally and good perspective for researching the deposits of construction stone. Keywords: diabase, ophiolitic melange, ore bearing formations, technical-construction stone, Kozara

1 INTRODUCTION

In the area of northern Kozara the ophio- and structural - texture characteristics, post- lites are represented by several blocks such magmatic processes and hydro-thermal al- as: Trnava, Vojskova, Balj, Mrakodol, teration, tectonic reshaping, etc.). Moštanica and Maglajci (Fig. 1). They are When the qualitative - quantitative indi- an integral part of the ore bearing formation cators (basic technical characteristics of of ophiolites „Ophiolitic melange of the rocks and possible application, possibility of north Kozara”, defined according to its dom- exploitation and stone processing, recovery, inant member, applying the criterion of pa- reserves, etc.) are included to the mentioned ragenetic formation analysis. geological parameters, possibilities for extra- Specifically developed parts of the ore ction a wide spectra of subformations and its formations are the ore subformations. Dur- ranking based on geological and economic ing defining of their specificities follo-wing significance can be revealed. Criteria and indicators were also used to determine the criteria have been used: level of magma potentiality of surfaces on which ophiolites solidification, manner of rock occurrence appear as rocks used as the technical buil- with different participation, mineralogical ding stone.

* Faculty of Mining Prijedor, University in Banja Luka, e –mail: [email protected] ** Mine and TPP Gacko, Industrial zone bb, e –mail:[email protected]

No. 3-4, 2020 1 Mining & Metallurgy Engineering Bor

2 OPHIOLITIC MELANGE OF THE

NORTH KOZARA (ORE BEARING FORMATION OPHIOLITES)

Unlike the southern area, where the op- dies, most often in a tectonic contact with hiolitic melange (diabase-chert formation) is the surrounding formations, rarely the con- of Jurassic age [1], northern Kozara includes tacts are the tectonic olistolytic. These larger a similar but younger formation defined as bodies account for about 80% of the surface the Cretaceous (tectonic) ''ophiolitic me- distribution of formation [3]. In the northern lange'' or ''ophiolitic complex'' [2]. The for- Kozara, the Trnava and Vojkova blocks are mation consists of a sedimentary matrix and highlighted, then the Moštanica block, Mra- blocks of different composition and dimen- kodol block and Maglajci block - the subject sions. The more prominent magmatic bo- of this paper (Fig. 1).

Figure 1 Geological map of the Kozara compiled from sheets the Basic Geological Map of SFR Yugoslavia, changed and supplemented [2, 9]

No. 3-4, 2020 2 Mining & Metallurgy Engineering Bor Igneous rocks are represented by gabrro, alternate on short distances. Basaltic effu- dolerite and diabase dikes and their systems, sions are usually solid with little dikes then basalts, acidic rock dikes and their vol- them break through. Basalts rarely contain canics. The variety in mineralogical and phenocrysts of plagioclass surrounded by chemical composition is the result of bimod- volcanic glass [9]. The formation matrix al intra-oceanic magmatism. Unlike the consists of alevrolites, sandstones, marls southern diabase-chert formation, no ultra- and limestones with all transitions be- mafits have been identified here. tween the last two members. It is a typical melange of tectonic origin. The Maglajci – Moštanica of ophiolitic It is genetically related to the finite, spatially zone is built by three ophiolite blocks with narrowed substantially narrowed parts of different geological and petrographic char- the Dinaric part of Tethys, when the process acteristics. Therefore, the magmatic rocks of its closure or collision begins. Based on of this zone are also classified into two ore the results of research on a "chaotic for- subformations. The first smaller Basaltic mation" in the western Serbia and Kosmet effusions of northern Kozara builds the [4], considering the similarities in the prop- western parts of the Maglajci block, while erties of blocks and time of their occurrence the other with the most acidic rock differen- with those in northern Kozara, as well as the tiators belong to the other igneous rocks. fact that they belong to the same regional geological unit the genesis of ophiolitic 2.1.1 Basaltic effusions of northern Kozara melange is interpreted partly by tectonic, (ophiolitic ore subformation) and partly by olistostromic [2]. The Cretaceous age of these formations The ophiolitic block Maglajci is located was assumed by Pamić and Jelaska [5], on the northern slopes of Kozara, south of based on the limestone fragments with cal- Kozarska Dubica and north of Prijedor. pionella and globotruncans in the melange, Border of blocks to the south make flysh and it has been proven by Grubic et al. re- sediments of the Lower and Middle Eocene cent provisions of globotruncans in red represented by conglomerates, sandstones limestones ”Scaglia Rossa“, which were and marls (E1,2), and the northern sides are intercalated by pillows – lava [6, 7]. The sediments of the terrigenous-carbonate for- mentioned biostratigraphic data are in ac- mation of the Lower and Middle Miocene cordance with the U-Pb ages obtained on and Sarmatian. zircons from the dolerites of the Vojskova The block is suitable for geological ob- block of 81.6 and 81.4 Ma, and also agree servations on the Maglajci deposit where, well with the K-Ar ages of 79 and 82 Ma, on the open profile about 50 m long and obtained from the ''whole rock'' dolerite about 20 m high diabases, the lava effusions from the Trnova diabase complexes [8]. occur, subordinate to wire, and in higher parts dominated by the ellipsoidal pillow 2.1 Maglajci – Moštanica ophiolitic zone bodies (Figs. 2 and 5). During magma cool- (ophiolitic ore formation) ing, the predisposed sputtering directions are created and a plate-like appearance of In the north of Kozara, the creations the basalt mass is formed. At the base of diabase - basalt - spilite - keratophyre as- profile, diabase occurs in a form of massive sociation rocks were selected that build to brechiated basin effusion (Fig. 4). The several ophiolitic blocks, out of which the rock here is not altered, dark gray to green- largest is the Vojskova block (Fig. 3). The ish-gray in color. The structure, individual rocks occur as fresh, altered and fractured fragments and appearance of the rock re- - intensely altered in the form of effusions semble pillow–lava, however, with more of magma, pillow–lavas and dikes and detailed observations, were found to be the

No. 3-4, 2020 3 Mining & Metallurgy Engineering Bor pseudo pillow–lavas. ''Chillded margins'' the variety “unaltered diabase”, whose occur in them as a result of the rapid lava thickness on the open profile of deposit cooling. The described rock corresponds to ranges from 10 to 12 m.

Figure 2 An open profile on the southern part of the Maglajci ophiolitic block

The contact of lava, massive diabase bodies formed by the rapid cooling of lava from the described open profile zone and in an interaction with water. They are pillow–lavas from the upper levels, is densely arranged and connected by a hy- marked with a hyaloclastic material. It is a aloclastic matrix which is somewhere volcanic glass that is finely splashed in solider, when it is silenced. ''Chillded contact with water as it forms and easily margins'' and intensely altered crust are alters. The thickness of this clearly visible observed along their edges. Their interior, contact zone is 0.5 m. In the southwestern unlike the edges, is solider with a rarely part of profile base, a dike of keratophyre seen ophitic structure. The thickness of was mapped, representing the impulse of this zone is up to 7 m. The rock has worse acidic magma through the basaltic effu- physical-mechanical properties, although sion (Fig. 3). The rock is light green with some zones look solid. a thickness of 0.6 m. Basaltic effusion are Although this is a small detected area mostly brecciated, so they are penetrated described relative to the surface of the by diabases and keratophyres. block western part, however, it can be In the upper levels, above the massive stated that its geological column generally basaltic effusion lava, pillow–lavas with a corresponds to the described local one, diameter of about 30 cm are represented which was confirmed by drilling and la- (Fig. 5). These are pillowy and ellipsoidal boratory testing.

No. 3-4, 2020 4 Mining & Metallurgy Engineering Bor

Figure 3 Formation draft of the Maglajci ophiolitic block

The rocks of this part of the block and thus the potential of ore formations that subformation are ophitic and porphyritic contain them. structures and of homogeneous and fluid The described creations of the western textures, and hypocrystalline and vitrophyr- part of ophiolitic block of the Maglajci are ic structures are represented. The geological of a great potentiality. They have relatively structure of block and structural characteris- low distribution and are excavated on the tics of diabase and basalt are closely related deposit of Maglajci. The highly promising to the genesis, that is, to the sudden outflow part is primarily marked by a massive to and cooling of magma in the marine envi- slightly brecciated basaltic outflow. The ronment, and with exogenous processes rocks are unaltered, solid with the good related to the crust of decaying diabase physical and mechanical characteristics: masses. So, this is a surface facies of the hardness to pressure 151.94 MPa; friction wear ''Los Angeles'' test (gradation B) 9,2 basic magma, and in the Maglajci block %; friction wear by the Böhme: 11.01 belongs to the volcanic level. Basaltic effu- 3 2 cm /50 cm ; water absorption 0.65% [10]. sions are massive or brecciated when pene- The crust of decay is variable and ranges trated by diabases and keratophyres dykes. from 14 m to 27 m. The areas of low per- Massive outflow is not suitable for the pro- spective are classified as the areas of cess of embossed. Embossed individual boundary part of the fog block where the dykes, especially acidic ones, not favorably diabase is decayed, dilapidated, tectonically have effect on the quality of rock mass, and processed and hydrothermally altered.

No. 3-4, 2020 5 Mining & Metallurgy Engineering Bor

2.1.2 Basaltic effusions with acidic rock differentiators of northern Kozara (ophiolitic ore subformation)

On the southern part of described profile pressure 123.68 MPa; friction wear ''Los of the block Maglajci, the pillow–lavas are Angeles'' test 19.22 %; friction wear by the pierced with several diabase polygonal ap- Böhme: 10.76 cm3/50 cm2; water absorption pearance up to 2 m thick. It is not possible to 0.14%. determine exactly whether the dike broke The Vojskova block with numerous fault through the entire mass or breakthrough zones, crushing zones, etc. also belongs to stopped at the observation site. The dike the subformation. In these zones, the rocks represents a channel through which magma are the most damaged, with the most of ex- penetrated and was eventually filled with pressed alteration processes. Pillow–lavas igneous materials. To the south, acidic dif- have been discovered at multiple sites and ferentiators dominate - quartz diabase, build mostly peripheral sections of the spilites, and keratophyres (Figs. 3 and 7). block. A sample of basalt-andesite from the Apart from the southern part of Magla- northeast part of block was tested for chemi- jaci block, subformation belongs to the cal composition on major and trace elements by the ’’whole rock’’ method, as well as Moštanica block in which with diabase and determination the absolute age of zirconia basalt represented keratophyres and granites. from dolerite by the U – Pb method [8]. The These are leucocratic rocks of massive tex- obtained age of dolerite on zircons by the U ture with a hypidiomorphic granular stru- – Pb method is 81.4 Ma and fits well with cture. The most common occurrence of the paleontological and other radiometric rocks are slabs of different thickness, less determinations from the entire ore for- than 1 m to several meters. Diabases appear mation. The Vojskova block is of a small as the rocks of ophitic structure, but porp- prospect, due to a large share of kera- hyritic varieties with large plagioclasses are tophyres in the entire rock mass, and then also significantly represented. There are due to a strong tectonic damage that caused often mandolas with interspaces filled with wear and tear and decay. This also resulted the secondary material. The ophiolitic block in a decrease in hardness to pressure, in- is of medium perspective with the good creased friction wear and water absorption, qualitative characteristics: hardness to and poor resistance to frost.

Fig. 4 Brecciated basaltic effusions of the de- Fig. 5 Pillow–lavas with core and hyaloclastic posit Maglajci have been pierced by the dyke material of the Maglajci block keratophyres

No. 3-4, 2020 6 Mining & Metallurgy Engineering Bor

Fig. 6 Crossing plagioclasses in diabase of Fig. 7 Micropiolytic strtucture in rhyolite the Maglajci block

3 CONCLUSIONS

- In the northwest of Bosnia and Her- - ''Basaltic effusions of northern Kozar- zegovina as a part of the regional tec- a'' builds the western parts of the tonic unit "Vardar zone western belt", Maglajci block, while the other the ore bearing formation ophiolites '”Basaltic effusions with acidic rock ”Ophiolitic Mélange of the north differentiators of northern Kozara” Kozara” is separated. The formation belongs to the other magmatic rocks. consists of a sedimentary matrix and - Basaltic effusions of the Maglajci blocks of different composition, block represent the ore subformation origin and dimensions. The more great prospects for the central parts prominent magmatic bodies, most of- with highly promising fields for ex- ten in tectonic contact with the sur- pansion the raw materials, whose cen- rounding formations. tral parts are highly potential for ex- - Each of the ophiolitic blocks, by itself panding the raw material base and or with blocks of similar genetic char- finding the new deposits. There are acteristics, represents a certain ore rocks with the good physical- formation of technical building stone. mechanical characteristics, and a wide Specifically developed parts of the ore domain of application in construction. formations are the ore subformations separated based on their geological REFERENCES and petrological parameters. These parameters, along with the qualitative [1] Jovanović Č., Magaš N., 1986: Expla- - quantitative indicators, mark poten- natory Book for the Basic Geological tial surfaces for finding the new de- Map SFRY 1:100.000, Sheet posits. Kostajnica. Federal Geological Survey, - The Maglajci – Moštanica ophiolitic Belgrade. zone is built by three ophiolitic blocks [2] Grubić A., Milošević A., Cvijić R., and two ore subformations with dif- (2018): Geology of the Mountains ferent geological and petrographic Kozara and Prosara. Monographs, characteristics. The first smaller Department of Natural – Mathematical

No. 3-4, 2020 7 Mining & Metallurgy Engineering Bor and Technical Sciences, Book 37. [7] Grubić, A., Ercegovac, M., Cvijić, R. Academy of Sciences and Arts of the & Milošević, A., (2010): The Age of Republic of Srpska. Banja Luka, Ophiolite Melange and Turbidites in pp. 241. the North-Bosnian Zone. Bulletin, [3] Milošević, A., (2013): Ophiolitic CXL, Academie Serbe des Sciences et Mélange of the North Kozara and des Arts, Classe des Sciences Mathe- Schistes Lustres of Prosara (Geology matiques et Naturelles, Sciences Natu- and Minerogeny). Doctoral Disser- relles, No. 46, pp. 41–56. Belgrade tation, Natural Mathematics Faculty in [8] Ustaszewski K., Schmidt S. M., Lugo- Banja Luka. pp. 131. Banja Luka. vić B., Schuster R., Schaltegger U., [4] Radoičić, R., (1997): On the Chaotic Bernoulli, D., Hottinger, L., Kounov, Formation of Rujevac and Veliki A., Fuegenschuh, B. & Schefer, S., Majdan (Western Serbia). Ibid, Book (2009): Late Cretaceous Intra-Oceanic 47, pp. 53–61. Belgrade. Magmatism in the Internal Dinarides (Northern Bosnia and Herzegovina): [5] Pamić, J., Jelaska, V., (1975): Occu- Implications for the Collision of the rrences of the Volcano-Sedimentary Adriatic and Europoean Plate. Lithos, Creations of the Upper Cretaceous and Vol. 108, Nos. 1–4, pp. 106–125. Ophiolitic Mélange in the North Elsevier. Amsterdam. Bosnia and their Importance in the [9] Cvetković, V., Šarić, K., Grubić, A., Geological Composition of the Internal Cvijić, R., Milošević, A., (2014): The Dinarides. Proceedings of the II Upper Cretaceous Ophiolite of North Annual Scientific Conference JAZU, Kozara – Remnants of an Anomalous pp. 109–117. Zagreb. Mid-Ocean Ridge Segment of the [6] Grubić, A., Radoičić, R., Knežević, Neotethys. Geologica Carpathica, Vol. M., Cvijić, R. (2009): Occurrence of 65, No.2, pp. 117–130. Bratislavа. the Upper Cretaceous Pelagic Carbo- [10] Milošević, A, (2020): Elaborate on nates within the Ophiolite-Related Classification, Categorization and Pillow Basalts in the Mt. Kozara Area Calculation the Reserves of Technical of the Vardar Zone Western Belt, Building Stone - Diabase on the Mag- Northern Bosnia. Lithos, Vol. 108, lajci Deposit near Kozarska Dubica. Nos. 1–4, pp. 126–130. Elsevier. Fund for Professional Documentation Amsterdam. of the Faculty of Mining Prijedor.

No. 3-4, 2020 8 Mining & Metallurgy Engineering Bor MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 681.325:622.33(045)=111 DOI: 10.5937/mmeb2004009V

Nenad Vušović*, Milica Vlahović**, Milenko Ljubojev***, Daniel Kržanović***

STOCHASTIC MODEL AND GIS SPATIAL ANALYSIS OF THE COAL MINE SUBSIDENCE****

Abstract

The occurrence of subsidence caused by the underground coal mining may be a complex process that causes damage to the environment. In the last century, there was a significant development in prediction methods for calculating the surface subsidence. In this paper, a new prediction method has been developed to calculate subsidence by combining a stochastic model of the ground movements and Geographical Information System (GIS). All the subsidence calculations are implemented by an original program package MITSOUKO, where the components of the GIS are used to fulfil the spatial analysis. This subsidence prediction technique has been applied to calculate the ground movements resulting from excavating 21 mining panels that are mined successively in the coal mine ''Rembas''- Resavica, Serbia. Details of movement were sequentially predicted and simulated in terms of years exploitation. Predictive calculation of the undermined terrain displacement parameters by the stochastic method and integration into the GIS is a powerful risk management tool. Keywords: underground coal mining; stochastic prediction method; GIS; spatial analysis

1 INTRODUCTION

The underground coal mining is accom- coal basin. The values of subsidence in the panied by a ground subsidence which pre- main cross sections by the seam strike and sents a pressing issue and needs attention in dip were obtained on the basis of type order to avoid its harmful effect on the sur- curves. They are the result of approximation face and subsurface structures. Therefore, and averaging of curves obtained by the prediction of subsidence using the reliable measurements or theoretical assumptions. methods is of a great importance. With the The analytical form of type curves, depen- aim to predict subsidence induced by the ding on the author, can vary (Averšin 1950; underground coal mining, the scientists from Kolbenkov 1961; Müller et al. 1965; N.C.B. all parts of the world applied various met- 1963; Anon 1975; Peng et al. 1981, 1993; hods, such as [1]: Kratzsch 1983; Hood et al. 1983; Kapp Empirical methods are the most nume- 1985; Whittaker and Reddish 1989; Kay rous group based on the results of systematic 1991; Holla 1997; Holla and Barclay 2000; measurements in the local conditions of a Seedsman 2001, 2004, 2006; Gale 2008).

* University of Belgrade, Technical Faculty in Bor, Vojske Jugoslavije 12, Bor, Serbia, E-mail: [email protected] ** University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Karnegijeva 4, Belgrade, Serbia *** Mining and Metallurgy Institute Bor, Zeleni bulevar 35, Bor, Serbia **** This work was financially supported by the Ministry of Education, Science and Technological De- velopment of the Republic of Serbia (Grant Nos. 451-03-68/2020-14/200131, 451-03-68/2020- 14/200026 and 451-03-68/2020-14/200052).

No. 3-4, 2020 9 Mining & Metallurgy Engineering Bor Profile function methods are based on roximated to the components that can be application the influence function of the definied and quantified since this view elementary excavated volume on the ground means understanding the physical beha- surface subsidence. They originate and were vior of attacked rocks. A reliable model is mostly applied in Germany, and their au- formed on the basis of defined mutual thors are: Schmitz 1923; Keinhorst 1925; interactions of components. Many theoreti- Bals 1931; Flaschentrager 1938; Perz 1945; cal studies and mathematical modeling of Sann 1949; Hoffman 1964; Daemen and the underground mining-induced surface Hood 1981; Peng and Chyan 1981; Kumar deformations are performed applying the et al. 1983; Karmis et al. 1984; Alejano et al. methods that rely on numerical models. The 1999; Díez and Álvarez 2000; Torano et al. most important methods are: the elastic 2003; Asadi et al. 2004; Zhao et al. 2004; methods and visco-elastic method. Numeri- Asadi and Shakhriar 2014. cal models include usage of the finite- Influence Function Methods was first element methods-FEM (e.g. Reddish 1984; proposed by Bals in 1931. In Poland, since Najjar and Zaman 1993; Yin et al. 2008; 1950 two influence function methods have Migliazza et al. 2009; Zhu et al. 2016; Liu been developed based on appying distribu- et al. 2017), boundary element method and tion of impacts using the Gaussian normal distinct element method in predicting the distribution curve (Budyk-Knothe 1953, ground subsidence and deformations. In 2005) as well as method by Kochmansky's addition, the numerical methods were used (1959) based on the distribution of impacts for the subsidence modeling and calculating on a specified derived curve. Using these the movement of rock strata (Yao et al. methods, a subsidence calculation can be 1989; Alejano et al. 1999; Zhao et al. 2004, performed for horizontal and slightly in- Keilich et al. 2006; Shabanimashcool and clined coal seams (Zenc 1969; Brauner Li 2012; Zhang and Xia 2013; Unlua et al. 1973; Marr 1975; Ren et al. 1987; Karmis et 2013; Zhu et al. 2016; Zhang et al. 2017). al.1990; Lin et al. 1992; Sheorey et al. 2000; Values of in situ rock mass parameters Álvarez-Fernández et al. 2005; Luo and are neccessary for all numerical models. All Cheng 2009; Luo 2015; Polanin 2015; Nie subsidence phenomena such as the decay of et al. 2017; Malinowska et al. 2020). Sto- rock, detachment, sliding, and rotation of chastic Influence Function Methods start seam cannot be quantified in laboratory from the assumption that the massif is lay- tests or incorporated into numerical models. ered, divided by a series of cracks into a The reliability of the prognosis depends on large number of rock blocks whose move- the number and degree of approximations of ments have a random character. The dis- the real conditions that are always involved placement of a rock massif, as the sum of the in the subsidence modeling. Manipulating movements of a large number of clastic el- certain parameters is usually necessary for ements, obeys the laws of mathematical obtaining a model which approaches the statistics (Pokrovsky 1929; Litwiniszyn measured subsidence profile results very 1957, 1974, 2014; Liu Bao-chen 1965; Pa- closely. taric and Stojanovic 1994; Vulkov 2001; The shape and position of subsidence Meng et al. 2014; Borela 2016; Cai et al. trough in relation to the excavated area de- 2016; Malinowska et al. 2020). pend on the geological and technological Numerical models. Theories of rock conditions of the underground exploitation. mechanics and mathematics are the base For the horizontal coal seams, a subsidence of numerical models for subsidence pre- trough is symmetrical in relation to the ex- diction. In mathematical modeling, the cavated area, while it becomes asymmetrical mechanisms of rock deformations are app- for the sloped coal seams.

No. 3-4, 2020 10 Mining & Metallurgy Engineering Bor Surface subsidence due to the under- that realistically simulate spatially distribu- ground mining and evaluation the subsid- ted, time-dependent subsidence processes ence-induced damages of objects are nowa- are desirable for the reliable design of mi- days growing problems in the Serbian coal ning layout to minimize the impact of un- mines with the underground exploitation. derground excavation on the ground sur- The sloped seams, with a thickness of 10-20 face. GIS is designed to support the integra- m at small and medium depths and an ex- tive modeling, perform an interactive spatial tremely steep relief as well as not large pop- analysis and comprehend different proce- ulation of the mine area, are specific for sses. Furthermore, based on the simulation Serbia. Material costs and psychological of complex subsidence processes that are responses have forced the underground coal spatially distributed and progressive in time, mining companies in Serbia to start resolv- it is possible to create the innovative the- ing these problems by the subsidence predic- matic maps containing the land-surface tion methods that minimize damages instead properties [5-8]. The stochastic calculation of previous repairing the buildings or com- model for the mine subsidence without GIS pensating their owners. would be time-consuming and very compli- The stochastic method proposed by the cated in cases of a large number of excava- authors Pataric and Stojanovic [2] has been tion areas [9-12]. applied for almost four decades in predic- The aim of this paper is to present a new tive calculations the subsidence at most approach for subsidence prediction, based brown coal mines with the underground on the stochastic Pataric-Stojanovic method exploitation in Serbia. The results of long- with integration into GIS, applied to the term measurements at these mines with exploitation of the "Strmosten" pit in the different naturally-geological and mining- underground coal mine ''Rembas''-Resavica technological conditions of exploitation (Serbia) for the period from 2018-2038. The indicated a correlation between the elements subsidence calculations are implemented by related to the cause- excavation of the coal the original program package MITSOUKO, seam and elements related to the conse- created by professor Vusovic, based on the quence - subsidence on the ground surface. Pataric- Stojanovic stochastic method. Spa- By comparison the calculated and measured tial analysis in GIS is based on the integra- values, it was revealed that using this sto- tion of the subsidence prediction results chastic method the extent of change on the using MITSOUKO software and data pro- ground surface can be successfully predict- cessing in the ArcGIS computer program ed, thus indicating the expected damage [13]. level of objects due to the subsidence above the mining works [3]. This confirmed the 2 STOCHASTIC METHOD FOR THE possibility of applying the stochastic Pa- MINE SUBSIDENCE PREDICTION taric-Stojanovic method for a reliable subsidence prediction. Ground movements, caused by the un- Modern geoinformation technologies derground coal mining, are very complex provided the use of progressive systems for and therefore difficult for modeling due to the management of spatial data with their the complicated behavior of the overlying integration in the Geographic Information rock mass and land profiles. In the mid- System-GIS. By general definition, the GIS twentieth century, for the mining-subsi- represents a ''…computerized database dence prediction, several idealized media management system for capture, storage, were used. Since the behavior of overlying retrieval, manipulation, analysis and display strata is complicated due to numerous of spatial (i.e. locationally defined) data'' known and unknown factors that affect and [4]. Computer-based analytical methods conduct moving of the rock mass, the sto

No. 3-4, 2020 11 Mining & Metallurgy Engineering Bor chastic theory of ground moving was used used method in China [23]. Nowadays, in these models for the mine subsidence SMTM is also used for calculating the prediction [14,15]. Generally, it is easier to ground movement caused by a tunnel con- predict the definite subsidence than the struction. The Stochastic Medium Theory movements caused by the sequential and Model arose into Probability Integral complicated mining processes. Therefore, Method-PIM, based on the statistical theo- the stochastic theory can be a universal ry which is more reliable and easier to use method for the mine-subsidence prediction for subsidence and deformations predic- [16-20]. tion in the entire excavation field [24].

2.1 The stochastic theory model 2.2 Stochastic method by Pataric and Stojanovic The idea of the stochastic theory model was introduced by Pokrovsky (1929) The Pataric-Stojanovic stochastic meth- and further was applied and developed by od presents a model based on the original the other authors of stochastic methods [2, mathematical formulas [2]. This method 14, 21, 22] . During studying the pressure applies the mathematical statistics and starts variation with a depth due to the concen- from the assumption of Litwiniszyn that the trated force on the surface, Pokrovsky massif is a multi-layered, divided by a series concluded that the pressure change at the of cracks into a large number of elements horizontal plane can be represented by the whose movements have a stochastic charac- standard Gaussian distribution curve. The ter [22]. This environment can be presented massif movement, which is a sum of by symmetrically arranged elements with movements a large number of clastic ele- the approximately similar dimensions. Such ments, obeys the laws of mathematical an area does not exist in nature, but this as- statistics. Litwiniszyn (1957) proposed the sumption is statistically correct because the stochastic subsidence model presuming pressure change curve in a homogeneous the ground mass as a discontinuous medi- medium is symmetrical and therefore ele- um where element movement towards a ments in the profile must be symmetrical. collapsing cavity is considered as the Owing to this symmetry, the force got by Markovian process [19]. According to the one element is transmitted and equally di- stochastic theory, moving of the rock mass vided into two parts on which it relies [25]. above the excavated element might hap- If the sides of the excavation panel are pen randomly with a certain likeliness 2a by the seam strike and 2l by the seam [22]. Numerous solutions of rock move- dip, the coordinate origin is at the inter- ment computing in various geological and section point of the rectangle diagonals, mining conditions have been realized and using the function: based on this stochastic method. This x 1 method proved to be effective allowing to 2  t 2 find the theoretical solutions to many  x   e 2 dt (1) problems [17]. Liu and Liao (1960) estab- 2 0 lished a stochastic method named the Sto- chastic Medium Theory Model (SMTM), a definite formula for calculating the sub- a profile function based on the statistic sidence during horizontal seam excava- medium algorithm method, for prognosis tion is obtained [2,25]. the underground mining-induced surface U x, y  U  X xY y (2) movement, which is the most commonly 0 0 0

No. 3-4, 2020 12 Mining & Metallurgy Engineering Bor where: The function  from expression represents the standard Gaussian distribution 1   a  x   a  x  curve. X 0 x          2   n   n  Equation (2) presents a general case for the subsidence calculation during ex- 1   l  y   l  y  Y0 y          cavating the horizontal seam of a rectan- 2 n n      gular area which is illustrated in Figure 1.

Figure 1 Subsidence during excavating the horizontal seam of a rectangular area with parameters: H - seam depth; 2a , 2l - dimension of excavation area; U - maximum max subsidence;  -draw angle;  - angle of maximum subsidence.

Basic formula for calculating the sub- , (3) sidence during inclined seams excavation U x, y  U0 X x, y Yy is obtained [2,25]: where:

1   a  x   a  x  X x, y    p     p  2        H ctg  y   H ctg  y 

1   b  m  y   b  m  y  Yy   q    q  2        H  ctg  y   H  ctg  y 

No. 3-4, 2020 13 Mining & Metallurgy Engineering Bor where:

p0 l cos H  cos p  , q  1  sin Q , b  , m  sin 1  sin 1  sin

The subsidence curve will be the same where Y y is calculated from the formu- in any profile by the dip, so it is a plane la (3). subsidence: Figure 2 presents subsidence during excavation of the inclined coal seam UyU0 Y y (4)

Figure 2 Subsidence during excavation of the inclined coal seam with parameters, , - angles of the draw.

In the case that   0, formula (3) is This study presents a predictive calcula- reduced to the basic formula (2) for calcu- tion of the subsidence based on the sto- lating the subsidence of a horizontal seam chastic method by Pataric and Stojanovic [2,25]. and GIS model using the input data from this underground coal mine in Serbia [13]. 3 RESULTS AND DISCUSSION 3.1 Characteristic of the research site The problem of subsidence and protecting objects above the mining works The ''Rembas'' coal mine is engaged in has been present for decades in the coal the underground exploration of a high- mine "Rembas"-Resavica with an under- quality brown coal. It is part of the Public ground exploitation of the "Strmosten" pit. company for the underground coal mining

No. 3-4, 2020 14 Mining & Metallurgy Engineering Bor ''Resavica'' (JP PEU ''Resavica''), the most firmed to i = 65%. Under the given condi- important center of underground coal mi- tions, it can be considered as the highest ning of the Balkan. Brown coal mine ''Rem- deposit recovery. The rate of caving ( q ) is bas'' has a tradition of coal mining for more adopted based on the analysis of the previ- than 150 years (wwwhttp://www.jppeu.rs). ous studying of the displacement process of Today, the "Rembas" coal mine consists of the undermined rock massif in the three production pits: ''Jelovac'', ''Strmosten'' "Strmosten" deposit. The value q = 0.70 is and ''Senj mine''. The "Strmosten" pit as well as its wider environment is formed of rocks accepted [13]. with the different lithological composition. The carboniferous Miocene series is inserted 3.2 Software solution for the mine between the cretaceous limestones and an- subsidence prediction based on desites, which form the paleorelief, and the the stochastic method Permian red sandstones. The Pliocene and The prediction of subsidence using the Quaternary sediments lie transgressively equations of the stochastic Pataric- across the Permian sandstones that represent Stojanovic method is a very complex the coal seam roof. The floor seam consists mathematical calculation considering the of clayey sandstones, clays, conglomerates accuracy of determining the input parame- and rarely of marl. ters, choice of density of the grid of points The coal seam thickness ( d ) is taken and interpolation of the subsidence con- from the geological interpretation of the tour lines, which would be a time- deposit and isolines of the main coal seam; it consuming in case of manual data pro- ranges from 2 to 8 m. The dip of coal seam cessing. Therefore, for internal purposes, ( ) is determined as the mean value of the original computer program package certain parts of an excavation field, with with the title MITSOUKO has been creat- values in the range of 5-15°. For the predic- ed based on the stochastic method pro- tive calculation of the subsidence parame- posed by Pataric and Stojanovic. ters, the mean values of the seam dip for The MITSOUKO program package en- each excavation panel (EP) are taken. Seam ables calculating the process of mine sub- depths ( H ) were determined based on the sidence at any point of the land surface and geological interpretation of the deposit with representating the results owing to possibil- the values ranged from 380-525 m. So far, ity of their integration and futher pro- during the exploitation of the "Strmosten" cessing in the GIS [25]. It offers the se- deposit several excavation methods have quential subsidence calculations by simu- been used in order to reach the optimal solu- lating the excavation process accor-ding to tions for very complex and difficult layer the adopted dynamics of mining the exca- conditions. Traditionally, the pillar excava- vation panels in the excavation field. The tion methods "G" and "V" were used, as MITSOUKO software is designed in the well as the longwall mining method with Python v. 3.8 programming language. mechanized hydraulic support. Coal deposit The excavation field, with a total area reco-very ( i ) is determined with losses of of 29 ha, is composed of 21 excavation g = 35%, which corresponds to the projec- panels, which are exploited one by one ted excavation method and its value is con successively from 2018 to 2038 (Figure 3).

No. 3-4, 2020 15 Mining & Metallurgy Engineering Bor

Figure 3 Excavation panels (EP) mined successively in the excavation field of the "Strmosten" pit [13]

The MITSOUKO software consists of returned by a module through the control two modules: PARAMETERS and SUB- loop. SIDENCE which represent the individual Firstly, by entering the MITSOUKO independent functions and are mutually program, in the PARAMETERS module, connected by a hierarchical structure [25]. the function (Eq. 1) is initialized, accord- Names of the modules suggest their func- ing to the tabular data [26]. Then, through tions and purpose in the MITSOUKO the menu, the data obtained based on ge- program. Each module starts with form ometric characteristics for each excavation according to a textual description explai- panel are entered: ID , dimensions ( a,l ), ning its name and function, tags of the seam depth ( H ), seam thickness ( d ) and input data that are loaded (Read parame- seam dip angle ( ). In the next step, in a ters) or computed (Calculate parameters) into a particular module, and data values specified subroutine of the PARAME-

No. 3-4, 2020 16 Mining & Metallurgy Engineering Bor TERS module, the following is calculated local coordinate system. During the calcu- for each panel: maximum subsidence (U0 ), lation for each excavation panel (EP), it is parameters ( m,b, p ), rate of caving ( q ), necessary to rotate its coordinate axes for the value of angle F (expressed in de- angles of draw (, , ), and angle of full i grees) to a direction of axes of the local subsidence ( ). The local coordinate system coordinate system. The calculated parame- is situated symmetrically with respect to the ters, together with the geometric charac- first excavation panel (EP1), with x -axis in teristics of each EP and information con- a direction of seam strike, y - axis in a direc- cerning their positions in the local coordi- tion of seam dip and coordinate origin in the nate system ( xi , yi , Fi ), represent the in- diagonal intersection of this panel. The posi- put data for subsidence calculation in the tions of all excavation panels ( xi , yi , Fi ) are SUBSIDENCE computational module determined with respect to the defined (Table 1).

Table 1 Input parameters for subsidence calculation [13]

Subsidences are calculated in the SUB- which is also the preparation of data for SIDENCE module. A certain subroutine graphical presentation and spatial analysis allows entering the coordinates of points in of these results in GIS. a grid of a given density, through the assigned distances between points ( x, y ), 3.3 Spatial analysis in GIS in the x and y axes directions of the local Spatial analysis in GIS is based on in- coordinate system. In this way, it is possible tegration the subsidence prognosis results to define the calculation limits for all panels obtained using the MITSOUKO computer up to a limit subsidence value of 10 mm. program package and data processing in Further, the subsidence values after mining ArcGIS [13]. The main steps in this inte- each panel are calculated cumulatively, gration are: transfer of mining subsidence according to the projected mining dynamics prediction tabular data from MITSOUKO of excavation field (Figure 3). The results of predictive subsidence calculation can be to GIS, building a geodatabase, spatial exported in tabular form in an Excel file, data analysis, and combination of maps individually for each excavation panel, layers to predict the subsidence [27].

No. 3-4, 2020 17 Mining & Metallurgy Engineering Bor GIS is used for creating a complex geo- playing feature classes from the ArcCatalog database, converting numerical data, im- (ESRI) is included. All the tables of the sub- ported from the SUBSIDENCE module, in sidence calculations have been transferred feature classes and graphical data as well as from the geodatabase coal mine to the for performing the spatial analyses of sub- ArcMap. sidence and deformations [6,7]. Since the The second step, Subsidence module, "Strmosten" pit consists of multiple EPs involves using ArcMap, which is an inte- with complex geometry, using the stochas- grated part of the ArcGIS software package, tic method for spatial analysis of subsidence to create layers for displaying feature classes requires a long time without GIS because taken from ArcCatalog (ESRI), then editing for each EP subsidence must be presented geometry and attributes of geoobjects, que- cumulatively, assuming all previous and rying spatial data and conducting spatial data current EP. analysis (geoprocessing) with a map crea- Implementing the stochastic method for tion. All tables of the subsidence calcula- spatial analyses of subsidence in GIS is tions have been transferred from the geoda- performed in two steps [25]: tabase "REMBAS" coal mine to the The first step, Data module, involves ArcMap. Using the Display XY Data com- creating a geodatabase of the "REMBAS" mand, the selected table of excavation panel, coal mine in ArcCatalog, within the ArcGIS e.g. EP21, which contains the x and y co- application (ESRI http://www.esri.com/ ordinates of the points and calculated sub- software/arcgis/) with feature classes, tables, sidence values, is added as a new layer in the and rasters. The feature class is a set of ho- Table of Contents. Thereby, a new feature mogeneous spatial attributes in the form of class, EP21_events, was formed, which for digitized vector data, in the same National this excavation panel EP21 contains 21760 Coordinate System (MGI Balkans7). In or- points with values of x and y coordinates der to integrate feature classes thematically and spatially into the mine model, within the and associated subsidences, georeferenced to given excavation panels (EP), feature da- the adopted coordinate system MGI Bal- tasets have been created, in which all types kans7. Following the same procedure, the of feature classes are entered. Feature da- new feature classes were created for all ex- tasets with feature classes related to the spa- cavation panels [13]. tial geometry: terrain topographies, build- The created feature classes contain ings, mining facilities, old mining works and and coordinates of all points in the grid new exploitation field in "Strmosten" pit, 10x10 m with associated subsidence values. excavation panels with mining dynamics by All the calculation results can be stored into years, active and old mining premises, and a GIS point-grid. The Spline interpolation geological interpretation of the coal seam are method from the Spatial Analyst Tools pal- created in a geodatabase of "Rembas"- Re- ette is then used to create the new layers savica mine. Outside the feature datasets, with contour subsidence lines for each exca- tables with subsidence, calculations from the vation panel (EP1-EP21), by cumulative SUBSIDENCE module in the MITSOUKO subsidence transformation from the previous program, rasters for the subject area in the to the new state. This provides a successive form of orthophoto, geographic maps, situa- following of the subsidence process on the tional plans of mine and photographs are map at all stages of the coal seam excavation imported in the geodatabase. Feature Da- in the "Strmosten" pit. The subsidence con- tasets have been created, in which all types tour lines are calculated from the maximum of feature classes are entered. Also, using the values to the adopted limit subsidence value ArcMap, an integrated part of the ArcGIS of 10 mm after mining the entire excavation software package, to create layers for dis- field in the "Strmosten" pit.

No. 3-4, 2020 18 Mining & Metallurgy Engineering Bor The third step involves the transfor- impact of mining works for all EPs was ana- mation of feature clases with subsidence lyzed. With the progress of mining, the sub- contour lines for each excavation panel de- sidence value for each EP is obtained cumu- termined in the local coordinate system to latively, that is, by superimposing the sub- the global MGI Balkans7 coordinate system sidence effects of all previously excavated in which a mine model of the respective panels and the actual one. observation field is presented [13]. Figure 4 shows excavations panels (from EP1 to EP20) in the coal mine "Rembas" 3.4 Subsidence analysis during mining Resavica - Serbia with the adopted excava- the excavation panels in the tion dynamics, subsidence contour lines "Strmosten" pit obtained by simulation the mine subsidence The stochastic method was used to cal- process by the stochastic prediction method culate the mine subsidence values in the and maximum subsi-dence values. MITSOUKO program package. The subsi- As it can be seen in Figure 4, the pre- dence contour lines are graphically presen- dicted maximum subsidence values on the ted in the ArcGIS software package by in- ground surface continuously increase from terpolation and cumulative transition from -1893 mm reached after excavation of the previous to the new state, formed on the EP3 in 2020 to -2927 mm after excavation data of the seam, and according to the of EP16 in 2033. Value of -2927 mm re- adopted excavation dynamics [7,9]. Based mains unchanged with further excavation, on the predicted subsidence values, the ending with EP20 in 2037.

Figure 4 Simulation of the mine subsidence process in the "Strmosten" pit [13]

No. 3-4, 2020 19 Mining & Metallurgy Engineering Bor

Finally, Figure 5 presents the mining op- value (U = -2927 mm) after mining 21 max eration plan and predicted subsidence con- excavation panels in 2038, that is the entire tour lines with the maximum subsidence excavation field in the "Strmosten" pit [13].

Figure 5 Subsidence contour lines after mining the entire excavation field in the "Strmosten" pit [13]

Figure 6 presents a digital elevation dence, with the maximum subsidence value model (DEM) of the final mine subsi- Umax = -2927 mm, in the "Strmosten" pit.

Figure 6 Digital elevation model (DEM) of the final maximum subsidence in the "Strmosten" pit [13]

According to the predictive calcula- value (- 2925 mm) after exploitation the tions, the maximum relative subsidence excavation panels EP1-EP15. With the was determined as the highest subsidence progression of mining operations, this

No. 3-4, 2020 20 Mining & Metallurgy Engineering Bor value grows towards the value of maxi- verified throughout the entire period of coal mum absolute subsidence. Maximum abso- seam excavation. This requires the syste- lute subsidence, U max =-2927 mm, is the matic geodetic surveying. The main goal of highest subsidence value, achieved after these surveying is to realize the surface sub- mining EP16, which does not increase with sidence process in space and time during the further mining works (EP16-EP21), but a excavation of the coal seam [28,29]. flat-bottomed subsidence trough, collapsed The basic grid for surveying consists of for that value, appears. The shape of subsid- profile lines arranged in directions of seam ence curve on the profile by the seam dip is dip and seam strike. This grid must satisfy in a fundibuliform. On the profile by the the requirement of long-term subsidence seam strike, the shape of subsidence curve is observations, which will last more than infundibuliform, but with a flat bottom in the twenty years so that the stability of bench- narrow central part of the curve, formed mark should not be compromised. Working because several points have the same value benchmarks are stabilized in the zone to be of the maximum absolute subsidence, affected by the subsidence process and by U max = -2927 mm. periodic defining the benchmark position, intensity, and state of the subsidence process 3.5 Mine subsidence monitoring for a certain period of time. Figure 7 shows the profile lines I-I and II-II for coal seam The values of the predicted parameters strike and coal seam dip with predicted subfor the ground surface subsidence should be sidence curves at cross sections [13].

Figure 7 Profile lines I-I and II-II for dip and strike of the coal seam with the associated predicted subsidence curves in the coal mine ''Rembas'' Resavica, Serbia [13]

No. 3-4, 2020 21 Mining & Metallurgy Engineering Bor

Geodetic surveying on profile lines program package, intended for the predic- gradually follow the general development of tive subsidence calculation according to the subsidence process through the data that stochastic method, which allows user to define the beginning of displacement, be- process a large amount of data, thus exclud- ginning of the intensive displacement phase, ing the time factor, and the obtained numer- intensive displacement phase, completion of ical data can be quickly and easily graph- this phase and regression phase process. ically processed and displayed in GIS. The extent, type of measurements, field The calculation of subsidence by the conditions and required accuracy of meas- stochastic method Pataric- Stojanovic and urements demand the application of modern integration with GIS is a powerful and reli- geodetic surveying methods and processing able tool for predicting the subsidence and of measurement results. Surface movement monitoring the impact of underground min- and deformations in wider areas have been ing works on the land surface. This work simpler monitored by introducing the air- presents an important research study, actual borne, satellite-based remote sensing tech- and significant for the mining profession niques, GPS and UAV systems (drones). and practice. The rapid development of remote sensing techniques such as LiDAR is leading to REFERENCES very high accuracy and cost-effectiveness and therefore more viable option. [1] Djordjevic D., Vusovic N., Prognosis The tabular and graphical processing of of the Displacement and Deformation the measurement results give the values of of the Underground Terrain, characteristic displacement parameters: University of Belgrade-Faculty of subsidence, horizontal displacement, slope, Mining and Geology, Belgrade, 2014. deformation and radius of curvature. The [2] Pataric M., Stojanovic A., Moving the subsidence trend during time is tracked on Underground Terrain and Protecting charts. There are two types of charts along Objects from Mining Works. the profile lines - the first are the subsidence University of Belgrade - Faculty of curves while the second are the parameters Mining and Geology, Belgrade, 1994. of displacement process in the form of dia- [3] Diyab RT., Comparative Analysis of grams of horizontal displacements, dia- Predicted and Measured Values of grams of slope change and diagrams of cur- Displacement and Deformation of vature change which serve to estimate the Undermined Terrain at Coal Mines in vulnerability degree of objects [1-3,13,25]. Serbia. Dissertation, University of Belgrade - Faculty of Mining and 4 CONCLUSION Geology, Belgrade, 2011. The stochastic method for the subsid- [4] Burrough PA., McDonnel RA., Principles of Geographical Information ence prediction and analysis of spatial data nd in GIS enable the calculation and presenta- Systems. 2 ed. Oxford, London, tion the subsidence on the surface of un- 2006. dermined terrain at any point in the grid [5] McDonald J., Evaluating Mine with a large number of numerical data Subsidence Using a GIS Software which require a long time of processing and Application, Conference: Digital interpretation of the obtained results by the Mapping Techniques’10,-Workshop standard data processing method. The an- Proceedings, Sacramento, California, swer to the set task lies in the MITSOUKO 2010.

No. 3-4, 2020 22 Mining & Metallurgy Engineering Bor [6] Cao J., Ma F., Guo J., Lu R., Liu G., [12] Unlua T., Akcinb H., Yilmaza O., An Assessment of Mining-Related Seabed Integrated Approach for the Prediction Subsidence Using GIS Spatial Regre- of Subsidence for Coal Mining Basins, ssion Methods: a Case Study of the Engineering Geology 166 (2013)186- Sanshandao Gold Mine (Laizhou, 203. Shandong Province, China). Environ- [13] Vusovic N., Technical Mining Project mental Earth Sciences 78 (2019) 25- for Determining the Parameters of 35. Displacement of Undermined Terrain [7] Cai Y., Jiang Y., Liu B., Djamaluddin and Protection of Sladaja Village I., Computational Implementation of a Objects from the Influence of GIS Developed Tool for Prediction of Underground Mining Works Above Dynamic Ground Movement and the "Strmosten" Pit at RMU "Rembas" Deformation due to Underground Resavica, University of Belgrade- Extraction Sequence, International Technical Faculty in Bor, Bor, 2018. Journal of Coal Science & Technology [14] Liu B., Liao G., Basic Regulars of 3(4) (2016) 379–398. Coal Mine Subsidence, China Industry [8] Trofymchuk O., Anpilova Y., Press, Beijing, China, 1965. Yakovliev Y., Zinkiv I., Ground [15] Kratzsch H., Mining Subsidence Deformation Mapping of Solotvyno Engineering, Springer-Verlag, Berlin, Mine Area Using Radar Data and GIS, Germany, 1983. European Association of Geoscientists [16] Vulkov M., About the Generalisation & Engineers, Conference Proceedings, Possibilities in a New Stochstical Geoinformatics: Theoretical and Model of Mining Subsidence, 50 Applied Aspects (2020), pg.1-5 - Years University of Mining and https://doi.org/10.3997/2214-4609. Geology “St. Ivan Rilski” Annual, Vol. 2020geo138 46, Part ІІ, Mining and Mineral [9] Esaki T., Djamaluddin I., Mitani Y., A Processing, Sofia, 2003, рp.153-154 GIS-based Prediction Method to [17] Djamaluddin I., Mitani Y., Esaki T., Evaluate Subsidence - Induced Evaluation of Ground Movement and Damage from Coal Mining Beneath a Damage to Structures from Chinese Reservoir Kyushu, Japan, Q J Eng Coal Mining Using a New GIS Geol Hydroge 41(3) (2008) 381-392. Coupling Model, International Journal [10] Esaki T., Zhou G., Djamaluddin I., of Rock Mechanics and Mining Development of GIS-based Rigorous Sciences 48(3) (2011) 380-393. Subsidence Prediction System for [18] Blachowski J., Application of GIS Protecting Surface Environment, Spatial Regression Methods in Environmental Rock Engineering, Assessment of Land Subsidence in Saito & Murata (eds) Swets & Complicated Mining Conditions: Case Zeitlinger, Lisse, 2003. Study of the Walbrzych Coal Mine [11] Miao F., Mingxing Y., Xiaoying Q., (SW Poland). Nat Hazards 84 (2016) Chengming Y., Baocun W., Rui L., 997-1014. Chen J., Application of DInSAR and [19] Borela VR., Stochastic Modeling and GIS for Underground Mine Subsi- DEM Simulation of Granular Media dence Monitoring, The International Subsidence due to Underground Archives of the Photogrammetry, Activity, Master Thesis, Purdue Remote Sensing and Spatial University, West Lafayette, Indiana, Information Sciences. Vol. XXXVII. 2016. Part B1. Beijing, 2008.

No. 3-4, 2020 23 Mining & Metallurgy Engineering Bor [20] Malinowska A., Hejmanowski R., Dai Stochastic Method Integrated with H., Ground Movements Modeling GIS, Mining and Metallurgy Institute Applying Adjusted Influence Function, Bor. No. 1 (2020) International Journal of Mining [26] Djordjevic D., Vusovic N., Ganic A., Science and Technology 30(2) (2020) Svrkota I., Angular Parameters of 243–249. Undermined Ground Movement [21] Knothe S., Equation of the Subsidence Process in Unknown Areas, University Profile. Archives of Mining and of Belgrade, Faculty of Mining and Metallurgy 1 (1953) 22–38. Geology, Belgrade Underground [22] Litwiniszyn J., The theories and Model Mining Engineering 19 (2011) 125- Research of Movement of Ground 136. Masses. In: Proceedings of the Euro- [27] Banerjee TK., Roy S., Dey S., A GIS pean Congress on Ground Solution for an Integrated Movement. University of Leeds, Underground Coal Mine Management: 1957, pp. 202–209. A Conceptual Framework, Journal of [23] Liu B., Theory of Stochastic Medium Management Policies and Practices and its Application in Surface 2(2) (2014) 129-143. Subsidence Due to Excavation, [28] Cui X., Wang JA., Liu Y., Prediction Transactions of Nonferrous Metals of Progressive Surface Subsidence Society of China, 2(3) (1992) Above Longwall Coal Mining Using a [24] Li P., Yan L.,Yao D., Study of Tunnel Time Function, International Journal of Damage Caused by Underground Rock Mechanics and Mining Sciences Mining Deformation: Calculation, 38(7) (2001) 1057-1063. Analysis, and Reinforcement, Advan- [29] Malinowska A., Hejmanowski R., ces in Civil Engineering Vol. 2019, Evaluation of Reliability of Subsidence pp.1-18. Prediction Based on Spatial Statistical [25] Vusovic N., Vlahovic M., Ljubojev Analysis. Int J Rock Mech Min Sci 46 M., Vlahovic M., Krzanovic D., (2009) 432–438. Software Solution for Mine Subsi-

dence Prediction Based on the

No. 3-4, 2020 24 Mining & Metallurgy Engineering Bor MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 622.33:621.879(045)=111 DOI: 10.5937/mmeb2004025B

Uglješa Bugarić*, Miloš Tanasijević**, Miljan Gomilanović***, Andrija Petrović*, Miloš Ilić***

ANALYTICAL DETERMINATION OF THE AVAILABILITY OF A ROTARY EXCAVATOR AS A PART OF COAL MINING SYSTEM - CASE STUDY: ROTARY EXCAVATOR SchRs 800.15/1.5 OF THE DRMNO OPEN PIT****

Abstract

Rotary excavators as the basic machines at the open pits of lignite operate in very difficult working conditions, where they are constantly expected to be highly productive, reliable, available and safe as the production carriers. Determining the availability as well as the duration and number of failures using the analytical methods allows to analyze the key influencing factors on their occurrence and values of these parameters and to determine the essential elements of system maintenance and management in order to optimize them. Keywords: rotary excavator, reliability, convenience of maintenance, availability

1 INTRODUCTION

Coal is the basic energy fuel in elec- systems with one export conveyor, with tricity production. Rotary excavators are occasional engagement of dragline excava- used to excavate coal at the open pits of tor as necessary auxiliary equipment. The the Electric Power Industry of Serbia. mined coal from both systems is transported Coal exploitation in the Kostolac basin by a groupage conveyor to the distribution began in 1870. The open pit "Drmno" is bunker and further to the crushing plant, the only active mine in the Kostolac basin. landfill and thermal power plant. The BTD The open pit “Drmno” produces 25% of systems are systems that consist of the fo- coal (lignite) in Serbia. llowing elements: a rotary excavator, series A growth of capacity on coal from the of conveyors and crushing plant. These sys- current 9x106 to 12x106 t/year and overbur- tems are connected in a series connection as den from 40x106 to the maximum 55x106 it can be seen in Figure 1. If one element of m3/year is designed at the open pit “Drmno“. the BTD system fails, the entire system stops Coal mining takes place with two BTD working.

* University of Belgrade, Faculty of Mechanical Engineering, Belgrade ** University of Belgrade, Faculty of Mining and Geology, Belgrade *** Mining and Metallurgy Institute Bor **** This work is financially supported by the Ministry of Education, Science and Technological Deve- lopment of the Republic of Serbia, Agreement on the realization and financing of scientific research work in 2020 for the Mining and Metallurgy Institute Bor, no. 451-03-68 / 2020-14 / 200052.

No. 3-4, 2020 25 Mining & Metallurgy Engineering Bor

Figure 1 Overview of the BTD system (rotary excavator-conveyor-crusher)

Equipment on the BTD systems: II BTD system: I BTD system: - excavator ERs 710.17,5/13-16; - excavator SchRs 800.15/1,5; - excavator SRs 400.14/1; - excavator SRs 400.14/1; - self-propelled conveyor BRs 2400; - 2 self-propelled conveyors BRs - self-propelled conveyor BRs 1400; 2400; - conveyor, width 1400 mm; - 2 level conveyors, width 1800 mm. - conveyor, width 1800 mm. [5]

Figure 2 View of the I BTD system at the open pit "Drmno"

This paper presents an analytical deter- A rotary excavator is in itself a very mination of the reliability and availability of complex machine system. Like any system, the SchRs 800.15/1.5 rotary excavator based it is composed of a number of subsystems: on the collected data related to delays (me- 1. Excavation subsystem chanical, electrical and other delays) on the I 2. Subsystem for excavator movement BTD system of the open pit "Drmno". 3. Receiving conveyor subsystem 4. Storage conveyor subsystem 1.1 Characteristics of an excavator 5. Subsystem for rotating the upper structure [4] The SchRs 800.15/1.5 rotary excavator According to the German classification, works within the I BTD system. The man- the rotary excavators are divided into classes ufacturer of this rotary excavator is the A (compact excavator), B (C frame excava- German company O&K. The excavator tor) and C (giant excavator) according to the was purchased in 1995. basic construction characteristics. [3]

No. 3-4, 2020 26 Mining & Metallurgy Engineering Bor

Figure 3 Types of rotary excavators [3]

This excavator belongs to a group of ristics of the SchRs 800.15/1.5 rotary exca- compact rotary excavators. Compact excavator are given in Table 1. In general, the vators have a relatively short boom in rela- operation technology of rotary excavators, tion to a diameter of the working wheel. [3] including this specific one, depends on three The advantages of compact rotary excava- basic factors: technological characteristics, tors are primarily in their low weight; there- geomechanical properties of the excavated fore, they have a lower purchase price and material and deposit conditions. The basic are characterized by the outstanding maneu- technology of SchRs 800.15/1.5 excavator verability. The disadvantages are reflected in operation is work in a height block (height the lower coefficient of utilization, high load work in a block with vertical cuts, excava- of a ball and frequent damage to the support- tion the entire block height in several cuts). ing structure. The basic technical character- The maximum floor height is up to 15 m.

Figure 4 Rotary excavator SchRs 800.15/.5 in operation

No. 3-4, 2020 27 Mining & Metallurgy Engineering Bor Table 1 Basic technical characteristics of the rotary excavator SchRs 800.15/15 [5] Theoretical capacity (m3/h) 3024 Guaranteed capacity (m3/h) 1350 Impeller diameter (m) 9.1 Installed drive power RT (kW) 800 Specific excavation force (N/cm) 1200 Nominal bucket volume (m3) 0.8 Number of buckets 14 Number of bucket shakes (1/min) 79 Excavation height (m) 15 Excavation depth (m) 1.2 Boom length RT (m) 14.5 Unloading belt length (m) 25.5 Height of the boom suspension point RT (m) 8.3 Suspension point distance from the vertical 1.2 rotary axis of the excavator (m) Boom angle RT () 19.5/15.5 Excavator weight in operation (t) 560

The rotary excavator works in very The reliability of a system of n series- difficult conditions, where a high produc- connected elements is equal to the product tivity, reliability, availability and safety at of reliability of all these elements. [1]. work are constantly expected from it as a carrier of production. The effects of operation the mining machines depend on the where: , ,... - reliability of system reliability, their functioning, technical and elements. [1] technological performance, handling, maintenance, logistical support, adaptabi- Structure of a system with a series lity-compliance of the relationship between connection of elements is the simplest the performance of machines and character- model of the system. istics of the working environment. [2] When there is a large amount of data on failures of system elements, as is the case in Reliability of systems with series this paper, there is a possibility to determine connected elements. Basic terms. the theoretical distribution of failure proba- Availability bility and repair of system elements. If the system has N series-connected Reliability is the probability with a certain level of confidence that the system, elements with different constant failure machine will successfully perform the intensities , ,..., , with exponential function for which it is intended, without distribution of element operating time to failure and within defined performance failure, then the distribution of system limits, taking into account the previous operating time to system failure is also time of the system use, during the given exponential, with intensity time of task duration. [1] . [1]

No. 3-4, 2020 28 Mining & Metallurgy Engineering Bor One of the most important indicators of the change in failure rate over time appears reliability is the intensity of failure. In a as in Figure 5. [7] large number of technical systems,

Figure 5 Function of failure interval density [7]

The curve in Figure 5, the so-called chine (technical system) spends "in fai- Bathtube curve, shows 3 areas in the life- lure". time of the technical system: Determining the availability makes it 1. Area of early failures possible to optimize the maintenance 2. Area with normal operation (period function, identify the important parame- of exploitation) - constant failure ters that affect the maintenance function rate, and represent the basic indicators of the 3. Area of failure intensification of fai- production system efficiency. lures - end of lifetime, [7] The availability of technical systems Maintenance convenience function The availability is calculated based on a In order for the machine (rotary excava- time state picture, in which the times when tor) to meet the high requirements when it the system in a good condition, the “up- comes to reliability, availability and safety in time” state, is changed with the times when operation, it is necessary to perform a the system is out of order, the “down-time” maintenance process. Convenience of maintenance is a very important feature of the state). The time picture of the state can be machine. It is a feature of an element or sys- shown in Figure 6. The time when the system that the maintenance measures can easi- tem is in a good condition can be divided ly prevent, detect or eliminate faults and into an inactive time, i.e. the time while the malfunctions. [1]. system is waiting for work (stand-by) ( ) The more complex the machine, the and the time when the system is working harder it is to detect failures. A large per- ( ). The time when the system is in failure centage of maintenance time is taken up by a is divided into: organizational time ( ), fault finding and thus increases maintenance logistic time ( ) and active repair time costs and production losses. ( ) which can be the time for corrective The maintenance function is defined repairs ( ) and time for preventive re- as the distribution of time that the ma- pairs ( ). [6]

No. 3-4, 2020 29 Mining & Metallurgy Engineering Bor

Figure 6 Time image condition [6]

The availability is determined as the bearings, cracking of caterpillars, tooth re- quotient of the total time during which the placement, etc.), electrical (cable break- system is in a good condition and the total down, TT connection interruption, interrup- time that makes the time in a good condition of blockage, etc.) were formed as well tion and time in failure (Operational avai- as the other failures (overhaul, service, con- lability). [6] ditional stop due to the bad weather conditions, etc.) of the SchRs 800.15/1.5 rotary ∑ ( ) [6] excavator for a period of 3 years (2016, ∑ 2017 and 2018). 2 DATA STRUCTURE OF FAILURE. Figure 7 shows the layout of one of da- STATISTICAL PROCESSING OF tabase. In each cancellation database there is FAILURE DATA a column in which the date, the object on which the failure occurred (delay), the be- There is no machine (rotary excavator) ginning of delay, the end of delay and the that works without failure. Failures on rotary total time in delay. excavators have negative production and Determining the affiliation of sample to economic effects, and the goal of mainte- the theoretical distribution can be done by nance and operation function is to minimize applying the 2 - test, i.e. the agreement of these negative consequences. empirical function F*(x) with the assumed A failure or malfunction is the cessation theoretical distribution function F(x) is of an element ability to perform its function. checked. [8] There is a complete (stoppage of the ma- The Hi-square test was used to deter- chine operation) and partial failure (the ma- mine whether there was a significant differ- chine operates but with worsened character- ristics). [1] ence between the expected frequency distri- Based on the data obtained from Ele- butions and observed frequency distributions ktroprivreda Srbije, which also includes the in one or more data categories. open pit "Drmno", databases related to the Table 2 shows the results of applying the mechanical (damage to the superstructure 2 - test.

Figure 7 Database form - electrical downtime

No. 3-4, 2020 30 Mining & Metallurgy Engineering Bor Table 2 Results of application the 2 test Distribution of Distribution between Ord. Delay Sample Object repair time failure times No. type size Type Parameter  Type Parameter 1. EXCAVATOR Electro 262 E1 0.016292425 E1 0.004015940 SchRs-800.15/1,5 2. EXCAVATOR Mechanical 359 E1 0.028463641 E1 0.002598397 SchRs-800.15/1,5 3. EXCAVATOR Others 161 E1 0.004390628 E1 0.004407482 SchRs-800.15/1,5 4. EXCAVATOR E+M+O 782 E1 0.019389661 E1 SchRs-800.15/1,5 E1 – Exponential distribution, – exponential distribution parameter - failure intensity,  – exponential distribution parameter - maintenance intensity.

Figure 8 shows the exponential distri- ure intensity) and parameters  (exponen- butions of electrical, mechanical and other tial distribution parameter - maintenance failures with the values of parameter intensity). (exponential distribution parameter - fail-

Failure Repair time (in failure) Operating time to failure (in operation)

type

Electro

. 2 2 25 . 5

Mechanical

. 2 . 25

No. 3-4, 2020 31 Mining & Metallurgy Engineering Bor

Others

. 2 . 2

Mechanical+Electro+Others

. Figure 8 Exponential distributions of electro, mechanical and other failures

maintenance intensity of the electrical elements of excavator maintenance intensity of the excavator machine elements maintenance intensity of the other failures maintenance intensity of the SchRs 800.15/1.5 excavator failure rate of the excavator electrical elements failure rate of the excavator machine elements intensity of the other failures

3 ANALYTICAL EXPRESSION FOR THE SCHRS-800.15/1.5 EXCAVATOR AVAILABILITY

3.1 Reliability of the SchRs-800.15/1.5 excavator

. 5 Reliability of the electrical elements of ( ) , excavator, based on the testing of sample of the operating time to failure, can be shown where: [1/h] - failure rate of the ex- by the exponential distribution forms: cavator electrical elements.

No. 3-4, 2020 32 Mining & Metallurgy Engineering Bor The average operating time between which means that the expected number of the failures, excavator electrical elements, failures of the mechanical elements of is equal to: excavator SchRs-800.15/1.5 for one year is equal to ~ 23. Reliability of the excavator connected . 5 to the other failures, based on the testing 2 . h. of sample of operating time to failure, can The function of restoring the electrical be shown by the exponential distribution elements of excavator ( ) is of the form: form:

. 2 ( ) . ( ) ,

For a period of one year (8760 h), the where: [1/h] – intensity of the other value of restoring function of the electrical failures. elements of excavator has the value: The mean operating time between other failures of excavator, is equal to: ( ) . 5 =35. , which means that the expected number of failures of the electrical elements of exca- . 2 vator SchRs-800.15/1.5 for one year is 22 . h. equal to ~ 36. Reliability of the machine elements of The function of restoring the other excavator, based on the testing of sample failures of excavator ( ) is of the of operating time to failure, can be shown form: by the exponential distribution form: ( ) . . 25 ( ) , For a period of one year (8760 h), the value of restoring function of the other where: [1/h] - failure rate of the excavator machine elements failures of excavator has the value: The mean operating time between failu- ( ) . 2 = res, excavator machine elements, is equal to: . , which means that the expected number of

. 25 other failures of the SchRs-800.15/1.5 excavator for one year is equal to ~ 39. . 5 h. The adopted principle at the open pits of The function of restoring the mechani- lignite of EPS, when it comes to consider the cal elements of excavator ( ) is of the failure of rotary excavators, is that the elec- form: trical, mechanical and other failures are in- ( ) . dependent of each other. If any type of fail- For a period of one year (8760 h), the ure occurs, the excavator stops working. value of restoring function of the mechan- Based on this, the reliability of the SchRs- ical elements of excavator has the value: 800.15/1.5 excavator can be shown by a

( ) . 25 = serial connection. (Figure 9)

22. ,

No. 3-4, 2020 33 Mining & Metallurgy Engineering Bor

Figure 9 Reliability of the SchRs-800.15/1.5 excavator - serial connection (electrical - mechanical - other)

Reliability of the SchRs-800.15/1.5 to electrical, mechanical and other fail- excavator ( ) is equal to: ures. The maintenance convenience function is of the exponential shape: ( ) ( ) ( ) ( ), ( ) ( ) ( ) . , . 2 , where: [1/h] – maintenance intensity where: [1/h] – failure rate of the of the SchRs-800.15/1.5 excavator SchRs-800.15/1.5 excavator The average repair time of the excavator, The unreliability function of the SchRs- the failure time, is equal to: 800.15/1.5 ( ) excavator is equal to:

5 .5 h. ( ) ( ) = . . 2 . The mean repair times due to the failures of electrical and mechanical elements The mean operating time of excavator and other failures are: between the failures, is equal to: Electrical:

. h. . 2

The function of restoring the excavator ( ) is of the form: h.

( ) . Mechanical: For a period of one year (8760 h), the value of restoring function of excavator has the value: h. ( ) Others: , which means that the expected number of failures of the SchRs-800.15/1.5 excavator for one year is equal to ~ 97 h.

3.2 Maintenance convenience function of 3.3 Availability of the the SchRs-800.15/1.5 excavator SchRs-800.15/1.5 excavator

The maintenance convenience function Statistical processing of data on operating time to failure and repair time of the of the SchRs-800.15/1.5 ( ) excavator was determined by testing a sample con- SchRs-800.15/1.5 excavator showed that the sisting of the time required for repair due unreliability function of excavator can be

No. 3-4, 2020 34 Mining & Metallurgy Engineering Bor described by the exponential distribution Finally, based on the results of statistical form ( ) , while the func- data processing on operating time to failure tion of benefits the excavator maintenance and repair time, the analytical expression for can also be described by the exponential availability of the SchRs-800.15/1.5 excava- distribution form ( ) . tor is of the following form:

( ) ( ) ,

( ) . 5 2 . . ,

where: – | ( ) | . availability coefficient, i.e. stationary availability value A. Solving the above inequality gives that: h. The approximate time , when the excavator availability reaches a stationary The change in availability of the value of A, can be determined based on SchRs-800.15/1.5 rotary excavator over the expression: time is shown in Figure 10.

Excavator availability SchRs-800.15/1,5

1.2

0.8

0.6

0.4

0.2

0 0 50 100 150 200 250 300 350 400 450 500

Time [h] Figure 10 The change in availability of the SchRs-800.15/1.5 excavator

4 CONCLUSION

The application of analytical method mination the key factors of system opera- for determining the availability and other tion as a function of time. By modeling parameters of the operation reliability of the work process as a function of time, rotary excavators allows efficient deter- applying the appropriate statistical met-

No. 3-4, 2020 35 Mining & Metallurgy Engineering Bor hods, the functional dependence of pa- [3] Polovina D.: Methodology for Deter- rameters such as availability, failure time, mining The Remaining Possibilities of work time, etc. is defined. as a function of Rotary Excavators in Exploitation and time. Revitalization - Doctoral Dissertation, In order to determine the relevant indica- University of Belgrade, Faculty of tors, it is necessary to have data on the oper- Mining and Geology, Belgrade, 2010 ation and failures of system for a longer period of time, and then to select the charac- (in Serbian) teristic cases. Within the selected character- [4] Vukotić V., Čabrilo D.: Increasing the istic cases, it is necessary to determine a Reliability of Excavation Subsystem of representative sample and perform the pre- a Rotary Excavator by Adjusting the sented analysis on it. Tribological Characteristics of Cutting Statistical analysis according to the pre- Elements, 13th International Confe- sented methodology and performed on a rence on Tribology Serbiatrib 13, 2013 representative sample, for the SchRs (in Serbian) 800.15/1.5 rotary excavator, shows that the [5] Milovanović I., Dimitrijević Ž., Vuč- intensity of all failures ( ) is 0.011021819 ković B., Radovanović B., Bogdanović and the maintenance intensity ( ) is 0.019389661. V., Stojanović S., Vučković M., Šuba- The values of these parameters indicate ranović T., Polomčić D., Božić M., at what stage of life time the rotary excava- Miletić D., Raščanin Z., Spasić A., tor is located. In the specific case, the rotary Milovanović S., Kulić Z., Lukić V.: excavator SchRs 800.15/1.5, according to Additional Mining Project of The the curve of tub, is in the operation phase, Open Pit "Drmno" for a Capacity of 6 which corresponds to the real situation. The 12x10 tons of Coal Per Year, PE EPS calculated parameters serve to determine the Belgrade, Branch RB Kolubara, availability of a specific rotary excavator Organizational Unit "PROJECT" and system as a whole, which is the basic Lazarevac, May 2019 (in Serbian) input data for production planning at the [6] Djenadić S., Ignjatović D., Tanasijević lignite open pits of EPS, but also the other M., Bugarić U., Janković I., Šuba- activities in the field of planning, monitoring ranović T.: Development of the of production or maintenance of equipment. Availability Concept Using The Fuzzy Theory with AHP Correction, a Case REFERENCES Study: Bulldozers at the Open-Pit Lignite Mine, Energies, October 2019. [1] Ivković S.: Failures of Mining Machine Elements, University of [7] Đurić R.: Concept of Availability in Belgrade, Faculty of Mining and Defining The Efficient Maintenance of Geology, Belgrade, 1997. Auxiliary Machinery at the Open Pits, Doctoral Dissertation, University of [2] Vujić S., Stanojević R., Tanasković T., Zajić B., Živojinović R., Maksimović Belgrade, Faculty of Mining and S.: Methods for Optimization the Geology, Belgrade, 2016 (in Serbian) Exploitation Life Time of Mining [8] Bugarić U., Petrović D.: Service System Machines, Faculty of Mining and Modeling, University of Belgrade, Geology, Belgrade, Electric Power Faculty of Mechanical Engineering, Industry of Serbia, Engineering Belgrade, 2011 (in Serbian) Academy of Serbia and Montenegro, 2004 (in Serbian)

No. 3-4, 2020 36 Mining & Metallurgy Engineering Bor MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 622.33/.272:6814.325(045)=111 DOI: 10.5937/mmeb2004037V

Nenad Vušović*, Milica Vlahović**

PREDICTION OF SURFACE SUBSIDENCE AND DEFORMATIONS DUE TO THE UNDERGROUND COAL MINING***

Abstract

Throughout its historical development, mining has faced the problem of moral and material re- sponsibility due to various types of endangerment and damage to the environment. As a result of the underground coal exploitation, a movement of the rock massif above the coal seam, and changes on the terrain surface due to the process of massif stabilizing take place. The process occurs in space and time, from the moment of balance disturbance in the massif, i.e., the beginning of excavation, during excavation, and after the final excavation of deposit, when the equilibrium state is reestablished in the massif. The character and intensity of these movements and principles according to which they are performed, depend on numerous natural and mining-technological conditions, and are specific to each individual coal deposit. Deformations on the terrain surface in the sinkhole occur in the horizontal and vertical directions. Their values serve to determine the vulnerability level of individual objects on the terrain surface. On the basis of the Patarić-Stojanović stochastic method for the predictive subsidence and deformations calculation, an original MITSOUKO program package, supported by the spatial analyses in the Geographic Information System (GIS), was designed. A case study in Sladaja village influenced by the underground exploitation in the coal mine "Rembas"- Resavica, one of the biggest Serbian coal mines, has been chosen. The data processed in the GIS provided determining the module, sense, and direction of the displacements, sinking velocity, and possible effects of subsidence on facilities. Keywords: underground coal mining, ground surface movements, stochastic theory, GIS, spatial analysis

INTRODUCTION

The surface subsidence and its harmful materials, which are often near and below effects on infrastructures above mining populated areas or natural and technical fa- operations is a serious problem resulting cilities, dictate the position of underground from the underground coal mining in min- pits and surface mines. It is truly claimed ing basins. The inevitability of conse- that the fight against these phenomena is the quences for objects on the terrain surface main feature of the entire mining history. can be related to the conditionality of the The environment and surface objects can be mine location. Deposits of mineral raw seriously affected by the subsidence [1].

* University of Belgrade, Technical Faculty in Bor, Vojske Jugoslavije 12 Bor, Serbia, e-mail: [email protected] ** University of Belgrade, Institute of Chemistry, Technology and Metallurgy, Njegoševa 12, Belgrade, Serbia, e-mail: [email protected], [email protected] *** This work was financially supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Grant Nos. 451-03-68/2020-14/200131 and 451-03- 68/2020-14/200026).

No. 3-4, 2020 37 Mining & Metallurgy Engineering Bor

STOCHASTIC MODEL OF THE GROUND SURFACE MOVEMENTS DUE TO THE UNDERGROUND COAL MINING

In the zone of mining works, an impact Surface subsidence can be caused by sinkhole occurs on the terrain surface. The the underground mining during operations shape and position of the sinkhole in rela- or later owing to deformations in the rock tion to the excavated space depend on the mass whereby the geologic factors such as mining and geological conditions of exca- the quantity and quality of the subsoil, vation. When the deposit lies horizontally, rock components and superficial condi- the sinkhole is symmetrical with regard to tions are of significant importance [4]. the excavated space, while with steep The developed subsidence prediction seams it acquires an asymmetrical shape. methods with different starting assumptions Damages due to the surface subsidence for deriving equations that describe the sub- can be provoked by the surface slope sidence curve are: profile function methods, changes, differential vertical displacements, inluence function methods, empirical meth- and horizontal strains and based on their ods and numerical models. Theoretical values, the vulnerability level for individual methods try to explain a mechanism that objects on the terrain surface can be esti- can predict the magnitude of subsidence: mated. Structural damages on facilities de- profile function methods are based on the pend on the construction method and used application of inluence function of the ele- materials; also, the chosen mining method mentary excavated volume on the ground has a great influence [2]. surface subsidence; influence function Case study presents a predictive calcu- methods are based on the effect of extrac- lation of the subsidence and deformations tion the infinitesimal elements of an area; based on the stochastic method by the empirical methods based on the results of Pataric and Stojanovic in the MITSOUKO systematic measurements in the local condi- program package, and the GIS model us- tions of a coal basin; numerical models use ing the input data from the underground the finite elements methods, boundary ele- coal mine "Rembas"- Resavica in Serbia. ments method, distinct elements method The calculated subsidence and defor- and finite difference methods to calculate mations in the analysed period have been the displacements and subsidence of ground presented graphically and described in the surface [3]. spatial analysis in GIS. Hence, the system Mining prophylaxy was greatly dis- created can be a useful tool to manage the subsidence data, determine its evolution, turbed and disabled because of the modest predict deformations and future environ- calculation capacity and lack of automa- mental and social impacts, and control tion. Computer technology and GIS ena- corrective measures. The application of bled benefits in this field [2,3]. the presented method supported by GIS on the chosen area enables a more automated Stochastic medium theory for subsidence assessment of building damage caused by and deformations prediction the mining activity. The procedure out- lined in this paper may also be satisfacto- Ground surface movements, caused by rily applied in the other counties which the underground coal mining, are very cope with the problem of building damage complex and therefore difficult for mode- risk assessment optimization [3]. ling due to the complicated behavior of the

No. 3-4, 2020 38 Mining & Metallurgy Engineering Bor overlying rock mass and land profiles. Since method, for the prognosis of underground the behavior of overlying strata is compli- mining-induced surface movement, which cated due to numerous known and unknown is the most commonly used method in Chi- factors that affect and conduct moving of na [7,8]. the rock mass, the stochastic theory of The Pataric-Stojanovic (1994) stochas- ground moving was used in these models tic method applies the mathematical statis- for the mine subsidence prediction. tics and starts from the assumption that the Generally, it is easier to predict the massif is multi-layered, divided by a series definite subsidence than the movements of cracks into a large number of elements caused by sequential and complicated whose movements have stochastic charac- mining processes. Therefore, the stochas- ter. Since the subsidence is plane, two tic theory can be a universal method for coordinates are sufficient: an abscissa par- the mine-subsidence and deformations. allel to the layers (horizontally) and an Litwiniszyn (1950) proposed a stochas- elevation vertically with the upward direc- tic subsidence model presuming the ground tion-to determine the position of elements mass as a discontinuous medium where an in the massif [9,10]. For the boundary element movement towards a collapsing transition from a discrete division to a cavity is considered as the Markovian pro- continuous massif, the starting point is the cess [5,6]. According to the stochastic theo- position of elements that are defined by ry, moving of the rock mass above the ex- the coordinates, i.e.: cavated element might happen randomly 1 with a certain likeliness. It assumes that the F x, z  h  F x  a, z F x  a, z , rock mass can be moved from one location 2 to another and its shape can vary under unit (1) element mining, however its total volume where F x, z is the function of subsidence remains the same. The procedure is based on the concept of stohastic process. Since its probability. beginning, this theory has undergone nu- Basic formula for calculating subsid- merous and constant improvements. ence during the inclined seams excavation Liu and Liao (1965) established a sto- is obtained: chastic method named the Stochastic Medi- U x, yU0 X x, y Yy , (2) um Theory Model (SMTM), a profile function based on the statistic medium algorithm where:

1   a  x   a  x  X x, y    p     p  2   H  ctg  y   H  ctg  y      

1   b  m  y   b  m  y  Yy   q    q  2   H  ctg  y   H  ctg  y       where: parameters: H - seam depth;  - angle of seam dip; p p  0 ; q  1  sin Q ; a - dimension of excavation area; sin

No. 3-4, 2020 39 Mining & Metallurgy Engineering Bor l cos H  cos rence of absolute subsidence values, or hori- b  ; m  ; 1  sin 1   sin zontal displacements of adjacent points, reduced to a length unit. cos q0   ; q  ; Based on their values, the vulnerability sin    sin level of individual objects on the ground surface is determined. Vertical deformations  - angle of full subsidence. are expressed through the slope changes and The stochastic subsidence prediction en- curvature of the terrain. Horizontal defor- ables the calculation and presentation of mations-dilatations, are expressed through surface subsidence at any point in a grid elongation or shortening of individual inter- with a large number of numerical data. The vals between adjacent points [11]. subsidence curve will be the same in any profile by the dip, so it is a plane subsidence: Slope

Uy  U0 Y y, (3) Subsidence values can only be measured at a limited number of discretely ar- where Y y is calculated from the Eq. (1). ranged points and the slope can be calculated from this data. The slope ( N ) repre- Deformations during subsidence sents the ratio of difference in the subsidence of adjacent points according to their Deformations are relative changes that distance. It is expressed in (mm/m). In occur as a result of uneven subsidence or fact, it is the mean slope between the ten- horizontal displacements on the undermined don AB of the subsidence curve and the terrain. They are calculated from the diffe- horizontal (Figure 1):

Figure 1 Slope [9]

With the coordinate origin above the U N  N   (4) middle of excavated space, the x -axis in a M  . direction of coal seam dip and the y -axis in In the general case, when the equation of a direction of coal seam strike, the slopes the subsidence curve U x, y is known, the   will be positive (+) by the strike and nega- point M and slope direction at that point tive (-) by the dip. must be given, because an unlimited number If the equation U  in a given profile of vertical planes can be placed through each point on the surface of subsidence curve, is known, its first derivative determines the whereby to each plane corresponds a diffe- slope of tangent at some arbitrarily chosen rent subsidence curve and thus the other point M , determined by the coordinate  : slope value (Figure 2).

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Figure 2 Slope value determination at a point M on the surface of the subsidence curve [9]

To solve practical problems, it is neces- Nx xM , yM   Nx M  sary to know the main slope in the plane, in which it has the maximum value. If  is a and vertical plane through a point M , which N y xM , yM   N y M . makes an angle  with the axis Ox (Figure 2), the coordinates of the point M are: Main slope. It can be seen from Eq. (5) that there is such a value of the angle xM  xA M cos    for which the slope at an arbitrarily 0 chosen point M will be N    0 , so yM  yA M sin , M 0 using: then, according to Eq. 4, the slope equation will be: Nx M cos0  N y M sin0  0 U x U y N    , it follows that: M x  y  N M  that is: tg   x . 0 N M  (6) U U y N   cos  sin (5) M x y . The angle 0 obviously determines a U U direction of subsidence contour line at the If  N x, y and  N x, y, x x y y point M . Also, a position of the plane  such that for a certain point M xM , yM  it follows the slope has an extreme value N  can that: M

No. 3-4, 2020 41 Mining & Metallurgy Engineering Bor N  be found; if    I is the angle determining M  0 , it follows that: that position, from the condition 

 N x M   sinI  N y M cosI  0 so it is: N M 1   N1M  is called the main N M y   slope at the point M [9]. tgI  (7) N x M  Based on Eq. (7) for known projec- tions and , using familiar The angle  determines the main di- NxM  N y M  I rection, and the extreme value of the slope trigonometric identities, the following can be calculated:

tgI N y M  sin1   2 2 2 1 tg I N x M  N y M 

1 N x M  cos1   . 2 2 2 1  tg  I N x M   N y M 

If these results are entered in Eq. (4), 2 2 the value of the main slope is obtained: N I M   N x M  N y M  . N   N M  (8) M 1 I Since the second derivative is:

2  NM   N x M cos  N y M sin N I M  0 ,  2 then this extreme value is also the maxi- and this normal. For example, it is the angle mum. that the axis of a pillar after the massif sink- From Eqs. (6) and (7), it follows that: ing will form with its original direction (ver- tg tg 1 0 , so the main direction tical). 0 I In practice, depressions and defor- I is perpendicular to the subsidence con- mations are most often determined in the tour line at the point M is: main profiles, in which their extreme values also occur. However, if the excavated sur- U x, y  UxM , yM   const. face is not full, i.e., the subsidence did not Since the main plane  I is determined reach its maximum possible value on the by the vertical and main direction  I , it terrain surface, general conclusions about these values cannot be made, neither the also contains the normal at the point M of places where the greatest deformations oc- sinkhole, and the main slope N M also I   cur, because the result depends on the exca- represents the angle between the vertical vated field [9,10].

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Curvature

Curvature represents the ratio of differ- (+) sign, and concave curves are negative ence in the slope of adjacent intervals and with a (-) sign, as shown in Figure 3. the mean value of their lengths. It is denoted Radius of curvature is the reciprocal by K , ant its unit is (1/km). With slope of curvature. It is denoted by R and its signs, the convex curves are positive with a unit is (km).

Figure 3 Curvature [9]

If the equation U   of the subsidence pler formula is used to calculate the curvature at a point: curve in the observed profile is known, its 2 first derivative defines the slope N U x  U  K    (9) and the second derivative determines the 2  curvature. The curvature at any point M Finally, if the equation of the subsidence determined by the coordinate  can be cal- sinkhole U x, y is known, a curvature can culated, using a known formula from differential geometry: be calculated at any point M x, y of the profile that angle  forms with the axis U  K     3/ 2 . Ox . From Figure 3, it is obvious that: 1  U  2  xM  xA M cos As the value of the slope is small, the 2 2 y  y  sin , member U     N () can be ne- M A M   glected in relation to the unity, so a sim so, based on Eq. (12):

2 2  2U  x  2U x y 2U  U  KM      2    , x2    xy   y 2    or, if shorter forms are introduced:

No. 3-4, 2020 43 Mining & Metallurgy Engineering Bor  2U  2U  2U K x  , K x  , K y  x2 y xy 2 y , it follows that:

2 2 KM   K x cos   2K xy sin cos  K y sin  . (10)

Instead of squares, i.e., products of 2 1 sines and cosines, a double angle can be sin   1 cos 2 introduced, based on the known trigono- 2 metric identities: and 2sin cos  sin 2 . So, a simpler form of the equation is 2 1 cos   1  cos 2; obtained: 2

1 1 K   K  K  K  K  cos 2  K sin 2 . M 2 x y 2 x y xy (11)

The members K and K in this extreme values of curvatures K and K x y I II formula according to Eq. (9) represent the at the point M x, y, which are called the curvatures at the point M x, y for pro-   main curvatures at a point, and the angles files parallel to the coordinate axes. The 1 and 2 of the corresponding profiles 2  U determine the main directions. According to third member, K xy  represents the xy Eqs. (10) and (11), the value of curvature at twist in a direction of coordinate axes at a point depends on the angle  , so deter- the point M x, y. miniation of extreme values of the function K  is mathematically reduced to the Main curvatures. To solve practical M   problems, it is necessary to determine the trigonometric equation:

K M    K  K  sin 2  2K cos 2  0 , (12)  x y xy whose solution: If trigonometric identities: 2K xy tan 2 2K xy tan 2  (13) sin 2   K x  K y 1 tan 2 2 K - K 2  4K 2 determines the main directions. If the main x y xy direction is known, the other is K  K o 1 x y   90   , because: cos 2   2 1 2 2 2 o 1  tan  K x - K y   4K xy tan 22  tan 180  21   tan 21 and are entered in Eq. (11), values of the main therefore  is the solution of Eq. 13. The 2 curvatures are: main directions are orthogonal.

No. 3-4, 2020 44 Mining & Metallurgy Engineering Bor 1 1 where: K  K  K  K  K  2 4K 2 I 2 x y 2 x y xy a  x  a  x  a  x  a  x  X 02x          (14)  n  n  n  n 

1 1 2 2 l  y  l  y  l  y  l  y  K II  K x  K y  K x  K y   4K xy Y x      2 2 02        n  n  n  n  . whereby K is the highest and K the I II lowest value of the main curvatures [9, 10]. Horizontal deformations - dilatations Members K , K and K are calcu- x y xy Horizontal deformations- dilatations, D , lated by the formulas: with the unit (mm/m), are determined from U the displacement of neighbouring points on K  0  X x Y y x 2 02  0  ; the terrain surface in the horizontal plane n (Figure 4) and expressed through elongation (+), or shortening (-) of the interval between U 0 adjacent points (Eq. 15): K y   X 0 xY02y ; n 2 P  D  (15) l U 0 AB K xy   X 01xY01y n2 where: P  PB  PA

Figure 4 Horizontal deformations- dilatations [9]

Elongation occurs if, after moving the and angle  between the line segments undermined terrain, the horizontal dis- A0 B0 and AB (Figure 4) can be found tances between adjacent points are in- analogously to the slope (Eq. 16): creased, and shortenings in the opposite case. When the points on the undermined P  P A  B massif surface move horizontally, defor-   , (16) mations similar to those during subside- l0 nce, also occur. Two arbitrarily chosen where PA and PB are the distances of points, A0 and B0 , of undisturbed massif, the points A and B from the original at a distance A B  l after consolida- 0 0 0 direction; the angle  is called the shear tion, move into position A , that is B , strain.

No. 3-4, 2020 45 Mining & Metallurgy Engineering Bor

Figure 5 Shear strain [9]

The shear strain at a point M x, y is o   ( ABC  90 ). Due to the rock massif un- calculated according to Eq. (17): dermining, there is a horizontal movement and these points move to positions A1 , B1 2 1  M  xy   xy cos 2  Dx  Dy  sin 2 and C , whereby, in general case, the angle 2 1 A B C is no longer a right angle. Shear (17) 1 1 1 whereby: strain of the line segment ( AB ),   AB  will be positive if   0 ; the 1  Py Px       , l1 xy 2  x y    deflection  is positive if   0 , so the AC   P P  change of right angle is  AB  AC . Half of 1  y x   xy     ; this change is slide: 2  x y  1     P       (18) Px y 2  l l  D  , D  .  1 2  x x y y As P  Px cos  Py sin , it follows where  xy denotes slide that will be ex- that: plained in the following text. P  Px cos  Py sin The points A , B and C of the undisturbed massif surface are at distances P  Px sin  Py cos AB  l and AC  l , and at a right angle 1 2

No. 3-4, 2020 46 Mining & Metallurgy Engineering Bor and: and B on their original direction A0 B0 , 1 according to Figure 5, it is obvious that:     xy cos 2  Dx  Dy  sin 2 2 l     l  P  P A B 0  A  B Half the difference l  l l0  P A  P B . 1            is rotation. This 2  l1 l2  In the general case P A  P B  0 , so quantity is not a deformation, because it l is an elongation when P A  P B , or a does not change the shape of triangle P  P  0 ABC , but only its rotation. For the point shortening when  A  B . rotation, the following can be applied: According to Eq. (15), the relation

1  Py Px  l        , D  is dilatation of line segment AB ;  xy 2  x y  l   0 it is the average elongation or the shortening so the shear strain at the point is the sum of this line segment. of rotation and slide: When the equations P x, y and x        M     . (19) Py x, y for horizontal displacements are known, the dilatation at a point is defined Main dilatations. If l  AB is the dis- analogously to the slope: tance between the projection of points A

P P  P P  P  x 2  y x  y 2 D   cos      sin cos  sin  (20)  x  x y  y .

If denotations and a double angle are introduced, the following is obtained:

1 1 D  D  D  D  D  cos 2   sin 2 . (21)  2 x y 2 x y xy

This formula has the same form as Eq. 1 1 2 2 D  D  D  D  D   4 . (11), so the main dilatations directions are II 2 x y 2 x y xy determined similarly as for curves [9,10]: Since the formulas have the same form 2 xy as those for the curvature, it follows that the tan 2  , (22) Dx  Dy sliding in the main directions is  12  0 , and the greatest sliding: as well as their values: 1 1 1   D  D  (24) D  D  D  D  D  2 4 2 xy 2 1 2 I 2 x y 2 x y xy

(23)

No. 3-4, 2020 47 Mining & Metallurgy Engineering Bor is for the axes Ox and Oy , which form enabling to distinguish the limits between o different intensities of damage, and to the angle of 45 with the principal axes. define the protection criteria. Such obser- PROTECTION OF FACILITIES AND vations were performed in many mining PROTECTION CRITERIA developed countries with different levels of population, in different mining condi- A protective pillar is a part of deposit tions, on facilities of different construction under a facility that is not excavated or is methods and characteristics, so that vari- excavated in such a way that no harmful ous protection criteria were created. The deformations appear on the object. The main difference between them is in terms endangerment of objects on the terrain of their generality, or their detail, which surface outside the boundary of the non- arises from the scope and level of study in excavated protective pillar, or within its the individual countries around the world boundaries if it is excavated, depends on [12,13]. In Serbian mining practice, there the type and value of deformations that are still no adopted criteria for the protec- may occur on the object [9]. tion of facilities from the impact of under- The type of deformation according to a ground mining works [9]. certain criterion depends on the object According to the Polish instructions type, and the level of these deformations for assessing the dangerous impact of depends on the construction of object. mining on buildings at the planned mining There are objects, in terms of damage, sites, which are most often used in solving sensitive only to a certain-primary type of these problems in the Serbian coal mines deformation, while the other types of de- [9], the basic criteria for protection of ob- formation are of secondary importance. jects are the allowed values of slope ( N ), Buildings and similar masonry buildings radius of terrain curvature ( R ) and hori- are most vulnerable to the horizontal de- zontal deformations - dilatations ( D ). To formations, which lead to the appearance determine the degree of dangerous impact of cracks. Tall buildings, chimneys, and of continuous deformations on the existing towers are sensitive to changes in a slope. and planned facilities in the analyzed area, The main structures (railways, roads, pipe- the mining terrain is divided into catego- lines) are sensitive to changes in curva- ries [2,12,14], whereby the limits are de- ture. There are objects of complex con- termined on the basis of the highest max- structions that are simultaneously vulner- imum values of deformations for a given able to the appearance of several types of category. Then the area of a given catego- deformations, and in that case, they must ry is determined by selection the maxi- be expressed through some common crite- mum ranges, which are the result of the rion [2,9,12]. least favorable distributions of specific A long-term observation of behavior deformation indices. Accordingly, the and damage of various facilities in differ- facilities are divided into four protection ent excavation conditions, empirical and categories (I-IV), whereby for each cate- statistical laws of occurrence of certain gory, the allowed values of deformations deformation types were obtained thus are prescribed, as shown in Table 1.

No. 3-4, 2020 48 Mining & Metallurgy Engineering Bor Table 1 Criteria for classification the surface movements and deformations [12]

Magnitude of expected deformations Usability for Terrain Possible degree of damaging; N D spatial category max Rmin max types of surface structures development (mm/m ) (km) (mm/m) 0 N <0.5 R 40 D  0.3 Small, easily fixable damage may occur. Safe areas, no Mo-numental objects, industrial systems, protection of ob- especially important for safety of life rea- jects is needed I <0.5 N 2.5 40> R 20 0.3< D 1.5 sons, or regarded as especially important, e.g., gas pipelines, the damaging of which may cause gas outbursts; water reservoirs. Small damage of objects may occur; rela- Areas, where tively easy to remove. The most important partial protection objects, industrial objects, large-furnaces, of all objects is coke furna-ces, hoisting shafts and ma- not profitable chines, Industrial objects-monolith or with overhead cranes, public utility objects, e.g., II <2.5 N 5.0 20> R 12 1.5< D 3.0 hospitals, theatres, vaulted churches), river valleys, water reservoirs, main railways and stations, tunnels, vaulted bridges, main water-works unprotected against mining damage, huge houses of residence (longer than 20 m). Big cities. Bigger damage of objects may occur, with- Areas requiring out destroying them. The main roads, routes partial protection and small railway stations, industrial objects of objects (type of which are less susceptible to the movement protection de- of the subsoil (no overhead cranes), uncoated pends on the type III 5.0< N 10.0 12> R 6 3.0< D 6.0 freezer-rooms, high chimneys, smaller of object, its houses of residence (10–20 m in horizontal sensitivity, subsoil prospection), city sewage treatment plants, properties, and main collectors, sewage pipelines, gas pipe- magnitude of lines, steel gas pipelines. deformations) Serious damage, objects are nearly de- Areas requiring IV 10.0< N 15.0 6> R 4 6.0< D 9.0 stroyed. Stadiums, small houses, other less serious protection important objects. of objects Areas which are V N >15.0 R <4 D >9.0 Very serious damage, objects are destroyed. not fit for spatial development

A CASE STUDY

The entire raw material potential of coal tectonics in the deposits. The seams from in Serbia, which is predisposed to the under- several to 40 m thick are from horizontal to ground exploitation systems, belongs to the steep. It should be added that the basic phy- JP PEU coal mines. In active coal deposits, sico-mechanical properties of the working the dominant geological forms are layered environment are relatively unfavorable be- sloped structures with the pronounced tec- cause predominant are the deposits where tonic deformations, whose consequences are the values of compressive strength of the irregular shapes of limited exploitation areas mine roof and floor are lower or significant- as well as possible short lengths of excava- ly lower than coal, which greatly narrows tion fields and panels with frequent changes the possibility for application of large mech- in the strike and angles of seam dip. These anized systems and concentration of produc- phenomena are the result of complex post- tion in them. In terms of the depth of coal

No. 3-4, 2020 49 Mining & Metallurgy Engineering Bor

Mine subsidence prediction based on

the stochastic method and spatial

analysis in GIS seams, most deposits belong to the group of The problem of surface subsidence and mines with a medium depth of exploitation, protecting infrastructure above the mining up to 500 m. The natural-geological condi- operations has been actual for decades in the tions in the deposits have a decisive role in “Strmosten“ deposit. In the Technical Min- choosing certain technological solutions of ing Project, the parameters of displacement exploitation, excavation systems (methods the undermined terrain and protection of the and technologies) and security measures in facilities of the Sladaja village from the im- the underground mining facilities [15]. pact of underground mining works above the "Strmosten" pit were determined [17]. Characteristics of the research site According to the stochastic Patarić- Stojanović method, subsidence at any point The "Strmosten" coal deposit has a syn- was calculated in the coordinate system cline shape whose wings spread to the placed in the centre of a certain excavation southwest. The axis of syncline extends panel (EP). This enabled to calculate the from the east and sinks to the west at an parameters of displacement process for each angle of 10-20°. Limestones form the rim EP and obtain complete information on the and, for the most part, the basis of produc- consequences of undermining on the terrain tive series, thus presenting the paleorelief of surface in the form of subsidence (U ) and basin together with the andensites. A deve- slope ( N ), cumulatively after successive loped coal seam with complex structure in mining of 21 EP in the excavation field OP2 the "Strmosten" deposit is stratified in three of the "Strmosten" deposit (Figure 6). parts in the northeastern area, and in two Calculating and graphical presenting parts in the central, eastern and western are- the subsidence of undermined terrain is as. The thickness of coal is from 2 to 8 m, on based on the originally developed soft- average 5.87 m at a depth of 380 to 525 m. ware application MITSOUKO and the The barren sediments in the layer are com- possibilities of spatial analysis in GIS, posed of marly and coal clays, marls, clayey which are the result of modern scientific sandstones and sandstones. Roof deposits, research [3,19,20,21,22]. Subsidence and with the exception of the roof immediately deformations using the MITSOUKO are above the coal seam which are of the Mio- calculated by the simulation of excavation cene age (red sandstones, marls, sandstones, according to the polygonal EP and adop- limestones and conglomerates) are most ted mining dynamics, whereby the results often homogeneous and undamaged. Most were integrated and processed in GIS [3]. of the roof sandstones are red sandstones, The basic formulas in the Patarić- and the conditions of collapse during exca- Stojanović stochastic method, contain vation and level of the manifestations of pit parameters dependent on the excavated pressures depend on their structural and space ( a,l,H,d,b ) and included in the mi- physico-mechanical characteristics [15,16, ning project, as well as parameters 17,18]. (U 0 , p, m, q ), which are not determined

No. 3-4, 2020 50 Mining & Metallurgy Engineering Bor in physical meaning, but define the be- connection with the geometric character- havior of the undermined terrain during ristics of displacement process in the consolidation and have to be brought into rock massif. Angles of draw ( 1, 1, 1 ),

Figure 6 Excavation field OP2 of the “Strmosten“ deposit [17] which limit the zone affected by the tematic subsidence monitoring in mines movements on the ground surface, and over the world were performed mainly on angle of full subsidence ( ), as the basic the surface of undermined terrain. Finally, angular parameters of displacement pro- Figure 7 presents the mining operation cess, are among them [17]. When deriving plan and predicted the subsidence contour the empirical formulas for the predictive lines with the maximum subsidence value subsidence calculation by the Patarić- (U max = − 2927 mm) after mining 21 ex- Stojanović method, all points of the massif cavation panels in 2038, that is the entire were observed, although the application of excavation field in the “Rembas” Resavica formulas is li-mited only to its surface- - Serbia coal mine [17]. undermined terain, since a long-term sys

No. 3-4, 2020 51 Mining & Metallurgy Engineering Bor

Figure 7 Subsidence contour lines after mining the entire excavation field in the coal mine “Rembas” Resavica- Serbia [17]

Vulnerability Assessment of the Cemetery in the Sladaja Village

The MITSOUKO software, in the The cemetery in the Sladaja village TILT module, calculates and tabulates the covers an area of 10100 m2 and a perime- slope components at the specified points ter of 426 m. Specific objects, such as of defined EP. First, the slopes in a direc- monuments in the area of the cemetery in tion of the absolute coordinate system, the village, are most sensitive to changes formed by excavating one EP, are calcu- in slope ( N ). On the other hand, this type lated, and then the procedure is repeated of objects is not affected by the horizontal for all EPs. The components of the total deformations ( D ) and radius of curvature slope in a direction of axes of the absolute of the terrain ( R ) because the dimensions coordinate system at a given point are of monuments are relatively small. obtained by summing the components of slopes of individual EPs [3,17].

No. 3-4, 2020 52 Mining & Metallurgy Engineering Bor To protect the terrain surface from subject area [18]. Based on the prediction [17], sidence, and thus the rural cemetery in the after excavation of all EPs without leaving a village, the management of the Rembas - protective pillar, the calculated subsidence Resavica mine decided to leave a protective values in this area were from U =- 2,200 pillar in a part of coal seam below the sub mm to U = - 2,920 mm (Figure 8).

Figure 8 Subsidence contour lines after mining the entire excavation field in the surrounding of the Sladaja village and cemetery [17]

Based on these subsidence data, the can be explained by the greater layer slope values were calculated for the pur- thickness ( d = 6.5 m), smaller excavation pose of determining the deformations in depth ( H ranged from 385 m to 415 m) the area of rural cemetery. The maximum and proximity of the old mining opera- slope was calculated at a value of N max = tions [17,18]. 11.0 mm/m in the eastern part at a very By comparison the calculated slope values with the allowable values, it can be border of the cemetery; slope values N in the central part of the cemetery ranged concluded that the maximum slope value from 2 to 7 mm/m and increased in the of 11 mm/m is below the allowable for eastern part to a value of 14 mm/m (Fi- objects of protection category IV (Table gure 9). Higher slope values in this part 1) [12,17,18].

No. 3-4, 2020 53 Mining & Metallurgy Engineering Bor

Figure 9 Slope values in the region of Sladaja village [17]

In the subsidence calculation, the de- serves in the OP2 excavation field of the posit recovery is taken with a value of "Strmosten" pit in RMU "Rembas" – Re- 65%, which can be considered as the savica a protective pillar should not be highest in the given conditions of mining left [17,18]. works of the "Strmosten" pit. According to the real estimation, the excavation loss- CONCLUSION es will be significantly higher, i.e., the recovery will be lower, so there is a cer- Deformations are relative changes that tain uncertainty in estimation the maxi- occur due to an uneven subsidence or hor- mum slope value on the terrain surface. It izontal displacements on the undermined is realistic to expect that the maximum terrain. Damages owing to the surface slope value will be significantly below the subsidence can be the result of surface calculated values in the area of cemetery slope changes, differential vertical dis- in the village [17]. placements, and horizontal strains. Based Based on the above facts concerning on their values, the vulnerability level for the predicted values of subsidence and individual objects on the terrain surface is slope, it can be concluded that under the determined. Case study presents a predic- area of cemetery in the Sladaja village tive calculation of subsidence and defor- when excavating the remaining coal re- mations using the input data from the un-

No. 3-4, 2020 54 Mining & Metallurgy Engineering Bor derground coal mine "Rembas"- Resavica Advances in Civil Engineering, Article in Serbia by the MITSOUKO program ID 4865161 (2019) 18. package, designed based on the stochastic [9] Patarić M., Stojanović A., Moving the Pataric-Stojanovic method, and supported Underground Terrain and Protecting by spatial analyses in the GIS. Objects from Mining Works, University of Belgrade - Faculty of REFERENCES Mining and Geology, Belgrade, 1994. [10] Djorđević D., Vušović N., Prognosis [1] Bell F., Stacey T., Genske D., Mining of the Displacement and Deformation Subsidence And Its Effect on the of the Underground Terrain, Environment: Some Differing University of Belgrade, Faculty of Examples. Environmental Geology 40 Mining and Geology, Belgrade 2014, (2000) 135–152. pg. 311. [2] Malinowska A., Hejmanowski R., [11] Meng F., Li-Chun W., Jia-Sheng Z., Building Damage Risk Assessment on Guo-Dong D., Zhi-hui N., Ground Mining Terrains in Poland With GIS Movement Analysis Based on Application, International Journal of Stochastic Medium Theory. Hindawi Rock Mechanics and Mining Sciences Publishing Corporation e Scientific 47 (2010) 238–245. World Journal, Article ID 702561 [3] Vušović N., Vlahović M., Ljubojev (2014) 1-6. M., Kržanović D., Software Solution [12] Malinowska A., Hejmanowski R., Dai for The Mine Subsidence Prediction H., Ground Movements Modeling Based on the Stochastic Method Applying Adjusted Influence Function. Integrated With The GIS. Mining and International Journal of Mining metallurgy Engineering Bor No. 1-2 Science and Technology, 30(2) (2020) (2020) 1-16. 243–249. [4] Sanmiquel L., Bascompta M., Vintró [13] Djamaluddin I., Mitani Y., Esaki T., C., Yubero T., Subsidence Evaluation of Ground Movement and Management System for Underground Damage to Structures from Chinese Mining. Minerals 8(6) (2018) 243. Coal Mining Using A New GIS [5] Litwiniszyn J., The Theories and Coupling Model. International Journal Model Research of Movements of of Rock Mechanics and Mining Ground Mass, Proceedings of the Sciences 48(3) (2011) 380-393. European Congress in Ground [14] Blachowski J., Application of GIS Movement, Leeds, 1957. Spatial Regression Methods In [6] Borela V. R., Stochastic Modeling Assessment of Land Subsidence In And DEM Simulation of Granular Complicated Mining Conditions: Case Media Subsidence Due To Study of The Walbrzych Coal Mine Underground Activity, Master Thesis, (SW Poland). Nat Hazards (84) (2016) Purdue University, West Lafayette, 997-1014. Indiana, 2016. [15] Ivković M., Systematization of [7] Liu B., Liao G., Basic Regulars of Natural-Geological Conditions of Coal Coal Mine Subsidence, China Industry Exploitation in the Underground Press, 1965. Mines in Serbia, Monograph, Committee for Underground [8] Li P., Yan L., Yao D., Study of Tunnel Damage Caused by Underground Exploitation of Mineral Resources - Resavica. Family Press, Kragujevac, Mining Deformation: Calculation, 2012 (in Serbian) Analysis, and Reinforcement.

No. 3-4, 2020 55 Mining & Metallurgy Engineering Bor [16] Patarić M., Supplementary Mining Damage From Coal Mining Beneath Project For The Exploitation Of The A Reservoir Kyushu, Japan. Q J Eng Main Seam at The "Strmosten" Pit, Geol Hydroge, 41(3) (2008) 381- Technical Mining Project for The 392. Excavation Impact on The Damage [20] Djamaluddin I., Mitani Y., Ikemi H., of Objects on The Surface. GIS-Based Computational Method Ugaljprojekat, Belgrade 1983. for Simulating the Components of [17] Vušović N., Technical Mining 3D Dynamic Ground Subsidence Project for Determining The during the Process of Undermining, Parameters of Displacement of International Journal of Undermined Terrain and Protection Geomechanics, 12(1) (2012) 43-53. of Sladaja Village Objects From The [21] Banerjee T. K., Roy S., Dey S., A Infuence of Underground Mining GIS Solution for an Integrated Works Above The “Strmosten” Pit at Underground Coal Mine Mana- RMU “Rembas” Resavica. gement: A Conceptual Framework. University of Belgrade - Technical Journal of Management Policies and Faculty in Bor, Bor 2018. Practices 2(2) (2014)129-143. [18] Djukić B., Vušović N., et al., [22] Cai Y., Jiang Y., Liu B., Supplementary Mining Project for Djamaluddin I., Computational Development and Excavation the Implementation of A GIS Developed Remaining Reserves in the Tool for Prediction of Dynamic Excavation Field 2 of the Pit Ground Movement and Deformation "Strmosten", The Mine "Vodna", Due to Underground Extraction RMU "Rembas" - Resavica, Sequence. International Journal of Ugaljprojekat, 2019 (in Serbian) Coal Science & Technology 3(4) [19] Esaki T., Djamaluddin I., Mitani Y., (2016) 379-398. A GIS-based Prediction Method To Evaluate Subsidence-Induced

No. 3-4, 2020 56 Mining & Metallurgy Engineering Bor MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 622.271.3/.46(045)=111 DOI: 10.5937/mmeb2004057I

Miloš Ilić*, Sandra Milutinović*, Branislav Rajković*, Daniela Urošević*

SELECTION OF A DEDUSTING SYSTEM FOR THE LIME STONE PREPARATION PLANT IN THE DEPOSIT "ZAGRADJE - 5"**

Abstract

This paper presents an example of a dedusting system in the deposit "Zagradje - 5" with the use of two different dedusting systems in order to more efficiently removal of harmful dust from the plant. The analysis is done by calculation and is a universal method of calculating the dedusting system, the results of which are necessary to verify the reliable operation of selected equipment. The technical characteristics of the filter and deduster as well as the technological scheme of dedusting are also given. Keywords: central dedusting, single deduster, bag filter

1 INTRODUCTION

The problem of clean, unpolluted air in working medium for mineral dust with 3 the industrial environments has become very less than 1% SiO2 is 15 mg/m . acute today, and it must be solved very The allowed concentration of dust in the quickly. The air we breathe at workplaces in air in the working environment is ensured by the factory halls is increasingly expressed in removal of dusty air from the source of dust the number of concentrated dust particles. In by forced air circulation by means of a fan fact, a large number of air pollutants in cities and its one-stage purification in the appro- come from industry. priate dedusting devices - bag filters so that This paper is aimed at sizing and se- the concentration of dust emitted into the lection of technological and mechanical atmosphere after purification is within the equipment that will ensure that the con- allowed limits. centration of dust in the plant that occurs According to the Decree on Limit Val- during operation is within the acceptable ues for Emissions of Pollutants into the limits [7]. According to the standard SRPS Air from the Stationary Pollution Sources, Z.B0.001-1991 [8] entitled the "maximum Except for the Combustion Plants (Offi- permissible concentrations of harmful cial Gazette of RS, No. 111/2015) [9], the gases, vapors and aerosols in the atmos- emission limit values for the total particu- phere of working premises and construc- late matter in waste gas are 20 mg/m3 for tion sites" ("Official Gazette of SFRY", the mass flow greater than or equal to No. 54/91), the maximum permissible 200 g/h or 150 mg/m3 for the mass flow of concentration of the total dust in the less than 200 g/h.

* Mining and Metallurgy Institute Bor, Zeleni bulevar 35 ** This work is financially supported by the Ministry of Education, Science and Technological Develop- ment of the Republic of Serbia, Agreement on the realization and financing of scientific research work in 2020 for the Mining and Metallurgy Institute Bor, no. 451-03-68 / 2020-14 / 200052.

No. 3-4, 2020 57 Mining & Metallurgy Engineering Bor

2 DESCRIPTION OF A TECHNOLOGICAL SCHEME OF DEDUCTING

Figure 1 shows the Technological shows the positions that will be processed scheme of dedusting installation, which in this text.

Figure 1 Technological scheme of dedusting installation

The central dedusting system will be jaw crusher. Through this feeder and one installed next to the open warehouses at slider (Pos.8.1), limestone is dosed in a positions 15.1,15.2,15.3, and after that, the controlled manner into the hatch of the individual dedusters will be used. C130 jaw crusher. The "Jaw crusher C The central dedusting system will use 130" performs the primary reduction of two HVP bag filters with involute input limestone size. 8HVP504, filter area: 453,274 m². Dimen- At the loading point above the primary sions of the HVP filter are: Ø4267.2 × crusher, a suction hood will be installed, 12911 mm. pos. N01 on a section D01 which extracts From the open pit "Zagradje -5", the the dusty air in an amount of 5000 m³/h, excavated limestone is transported by wherein the concentration of dust of 11.5 trucks to the shaft pit, where there is a g/m³. Via the slide (Pos.8.1), the primarily robust steel grid with square openings. crushed limestone is directed to a belt Limestone passes through the grid and conveyor Pos. T-1 which transports the then falls into the shaft pit. It descends material to the conveyor at position T-2, directly to a jaw crusher. A feeder with which transports the limestone to the pri- chains (Pos.6) is provided in front of the mary screen (Pos. 9.1).

No. 3-4, 2020 58 Mining & Metallurgy Engineering Bor A suction hood, pos. N02, is installed is directed to the conveyor Pos. T-5, which at the unloading point of the crusher, deposits this size class, which is the first which sucks out dusty air in the amount of finished product of the limestone prepara- 14000 m³/h, where the dust concentration tion plant, to the first open warehouse is 11.87 g/m³ on section D08. (Pos.15.1). From there, this size class A suction hood was installed at the pres- - 80 + 40 mm through concrete openings sure point pos. N03 between the belt con- and 4 bars (Pos.8.19-4) and 4 vibrating veyors T1 and T2, which sucks out dusty air feeders (Pos.17.1) is dosed to the conveyor in the amount of 3350 m³/h, where the dust with a rubber conveyor belt Pos.T-8, which concentration is 6.5 g/m³. The sieve has a this size class, i.e. the finished product of sieving surface of 11.4 m² and circular crushing and screening is transported to the openings of the sieving surface of the sieve conveyor on Pos.T9, more precisely it is of 88 mm (separation 80 mm). A suction connected to this conveyor. Via the con- hood, pos. N04, is installed above the sieve, veyor T9, which will work in alternating which sucks out dusty air in the amount of mode with the conveyor T8, i.e. the alternat- 9800 m³/h. ing functioning and dosing of the material The screening of the sieve at Pos.9.1 will be provided, via the reversible convey- through one slide (Pos.8.3) is directed to the or T11, to the receiving bunkers of the lime receiving hopper of small capacity (Pos.10) plant (Pos. 13 and 14).The sieving of the below when there is a belt feeder T3 secondary sieve CVB 302P of the I sieving (Pos.11). The mentioned feeder doses lime- surface, size class - 40 + 0.0 mm, imme- stone into the hatch of the secondary Cone diately falls on the II sieving surface of the crusher HP300 in which the secondary re- sieve CVB 302P (Pos.9.2) on the third siev- duction of the size of limestone is per- ing. The screening of this sieve CVB302P formed (Pos. 12). A suction hood, Pos. N05, (Pos.9.2) II sowing surface, size class - 40 + will be installed in the recessed place above 20 mm, is the second finished product of the the crusher, as well as at the exit from the limestone preparation plant. This size class crusher Pos. N06. An exhaust hood N07 -40 + 20 mm, i.e. the screening of the sieve will be installed at the loading point of the II of the sieving surface is directed via one T4 belt conveyor from the sieving of the slide (Pos.8.7) to the conveyor Pos.T-6, CVB301P sieve. which deposits this class of size to another The crushed material of the secondary open stack (Pos.15.2). From there, this size crusher HP 300 is combined with the sieve class - 40 + 20 mm is dosed to the trans- of the primary screen CVB 301P where porter with a rubber conveyor belt via con- another hood Pos. N07 will be installed, crete openings and 4 bars (Pos.8.10-4) and 4 where the air capacities are 4000 m³/h, vibrating feeders (Pos.17.2). T-9 which this 8500 m³/h and 5400 m³/h, respectively. The class of size i.e. the finished product of material is then transported with a T-4 con- crushing and sifting is transported to the veyor to the sieving via a slide (Pos. 8.5), on receiving bunker of the lime plant (Pos 13). a secondary sieve CVB 302P (Pos.9.2) Therefore, the two main products, fractions manufactured by Metso minerals. The sieve -80 + 40 mm and -40 + 20 mm, will be has two sieving areas of 11.4 m2. Above the transported to the receiving bunkers, Pos.13 sieve is placed the hood Pos.N08. The and 14, via the reversible conveyor T-11. openings of sieving surfaces of wire panels This further means that the T-8 conveyor, as are: 48 × 48 mm (separation 40 mm) and already mentioned in the text, "connects" to 23 × 23 mm (separation 20 mm). Screening the T-9 conveyor, which disposes of the of sieve I, sieving area on (Pos.9.2) size mentioned fractions in the receiving bun- class - 80 + 40mm over one slide (Pos.8.7) kers via the T-11 reversing conveyor, each

No. 3-4, 2020 59 Mining & Metallurgy Engineering Bor intended for a specific fraction. While the individual dust collectors, manufactured conveyor T-8 is in operation mode, and by KDK-EKO or similar, will be installed delivers the size class - 80 + 40 mm, from at the filling points pos. NO12-NO17. the warehouse Pos.15.1, to the conveyor All dust will be unloaded from the T-9, it is clear that the dosing of product central dedusting system from these two -40 + 20 mm, through the warehouse 15.2, HPV filters into two pyramidal steel dust will be suspended and vice versa, when collection bunkers, and from there via dosing, i.e. feeding the bunker pos.13, telescopic devices for unloading material with the product - 40 + 20 mm, via the into trucks. conveyor T-9 and T-11, feeding the bunker Pos.14 with the product - 80 + 40 mm, 2.1 Calculation of the Suction Air via the conveyor T-8, T-9 and T-11 will Quantities be suspended. The introduction of the T-11 reversible conveyor enables uninter- The quantities of exhaust air for all rupted feeding of the provided bunkers for exhaust points are given in Table 1. the appropriate required products, while The quantities of exhaust air for loading the alternating operation of the T-8 and places NO1, NO2, NO5 and NO6 were T-9 conveyors, more precisely the alter- adopted from the literature No11k [1]. For nating dosing of materials from open loading places NO7, NO9, NO10, NO11, warehouses to the mentioned conveyors, NO12, NO13, NO14, NO15, NO16, NO17, enables uninterrupted transport of defined NO18, the Molčanov [2] calculation meth- products without mixing them. od was used. And for loading places NO4 Above the CVB302P vibrating screen, a and NO8, the Volkov method was used. NO8 extraction hood is provided for an air The Molčanov calculation method is the volume of 10200 m³/h at a dust concentra- following: tion of 11 g/m³. The quantity of suction air is calculated A closed hood will be installed at the according to the following formula: loading point of screening sieves on the belt [ ⁄ ] conveyor Pos. NO9, for the air capacity of 2650 m³/h, and at the unloading places Pos. where: NO10 and NO11 on belt conveyors T5 and - quantity of air introduced by T6 hoods for the air capacity 2300 m³/h and material 1700 m³/h, respectively, where the dust - quantity of air entered through concentration for all three suction points is the openings 6.5 g/m³. Quantity of air introduced by material Furthermore, sieve of the screen is calculated by the following formula: CVB302P class size - 20 + 0.0 mm is a product that is transported by conveyor [ ⁄ ] Pos.T-7 to the third open warehouse where: (Pos.15.3) and which will be through 4 - coefficient (depending on construc- concrete openings and 4 bars (Pos.8.11- 4) tion and type of material) - in this and 4 vibration feeders (Pos.17.3) for fur- case we adopt 1.4 for ordinary loa- ther treatment should be sent to a new ding troughs conveyor with a rubber conveyor belt Pos. – volume flow of material T-10, on micronization in the lime plant. – final speed of material Individual dust collectors PO1-PO7 with compressor stations for production The final speed of material is calcula- the compressed air for impulse blowing of ted by the following formula:

No. 3-4, 2020 60 Mining & Metallurgy Engineering Bor

√ ( ) [ ⁄ ] where: where: H – height of material drops – volumetric flow of material - coefficient of material friction aga- – final speed of material inst the walls (according to the document SN 155-61[3] it can be seen for Final speed of material is calculated by lime 0.56) the following formula: - inclination angle of a section √ ( ) Volume flow of material is calculated: where:

[ ⁄ ] H – height of material falls

- coefficient of material friction where: against the walls (according to the Q – mass flow of material document SN 155-61[3] it can be - bulk density of material (according seen for lime 0.56) to OHTII-10-85[4] for lime is 1.5 - inclination angle of a section

[ ⁄ ]) Volume flow of material is calculated:

The quantity introduced through the [ ⁄ ] openings is calculated by the formula: where:

Q - mass flow of material where: - bulk density of material (according A - coefficient for material loading from to OHTII -10-85[4] for lime is 1.5 a belt conveyor [ ⁄ ]) C – coefficient for a belt width 800 mm The quantity introduced through the - coefficient for impassable loading openings is calculated by the formula: place B – width By Volkov[5] the quantity of suction where: air for sieve is calculated by the formula: F– surface of tightness - air speed through tightness (by Vol-

[ ⁄ ] kov [5] it can be adopted for sieves of 2) where: – quantity of air introduced by material where: – quantity of air that enters through 0.1 - coefficient of tightness (by Volkov the openings it can be adopted for sieves of 0.1) The amount of air introduced with the P – surface material is calculated according to the Table 1 is formed on the basis of given following formula: calculations.

No. 3-4, 2020 61 Mining & Metallurgy Engineering Bor Table 1 Amount of suction air in the limestone preparation plant Amount of air in Dust concentration in Suction mark m3/h g/m3 NO1 5000 11,50 NO2 14000 12,00 NO3 3350 6,50 NO4 9800 11,00 NO5 4000 20,00 NO6 8500 20,00 NO7 5400 6,50 NO8 10200 11,00 NO9 2650 6,50 NO10 2300 6,50 NO11 1700 6,50 NO12 1260 6,50 NO13 1700 6,50 NO14 1260 6,50 NO15 1700 6,50 NO16 1260 6,50 NO17 1700 6,50 NO18 2520 6,50

2.2 Dust Concentration at Suction Points

For dust concentration at suction points, Following the example of calculation the recommendations for certain devices, the dust concentration on the following given in the literature SN 155-61[3], were sections, Table 2 is given. used.

Figure 2 Section view

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[ ⁄ ] where: – air quantity in given section

[ ⁄ ] where: – dust concentration in given section

Table 2 Air quantities and dust concentrations in given sections Amount of air in Dust concentration in Section mark m3/h g/m3 D01 5000 11,50 D02 19000 11,87 D03 22350 11,06 D04 50500 12,80 D05 66900 11,90 D05a 33450 11,90 D05b 33450 11,90 D06a 33450 0,0119 D06b 33450 0,0119 D06 66900 0,0119 D07 66900 0,0119 D08 14000 12,00 D09 3350 6,50 D010 8500 20,00 D011 12500 20,00 D012 22300 16,04 D013 27700 14,18 D014 4000 20,00 D015 9800 11,00 D016 5400 6,50 D017 2650 6,50 D018 4950 6,50 D019 15150 9,53 D020 16850 9,22 D021 2300 6,50 D022 1700 6,50 D023 10200 11,00

Based on the given parameters, the system equipment in the limestone prepa- machine design and selection of dedusting ration plant is done.

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3 TECHNICAL DESCRIPTION OF A

DEDUSTING SYSTEM

The dedusting system of the limestone conical part of the filter. From the conical preparation plant comprises two units or part of the filter, dust is discharged into phases. Phase 1 includes a transport sys- bunkers via a star feeder on electric drive. tem from the primary crushing to the two- Phase 2 includes dedusting of the load- level sieve facility, and since it is a de- ing parts of conveyor, and since the pendent system that is in operation at the transport system is independent, i.e. the same time, a central dedusting system is conveyors work independently of each oth- adopted where dust is suctioned from all er, an individual dedusting system was dust sources that are in operation at the adopted. The mentioned system is based on same time. purification the dusty air in a deduster itself The central filter plant is located on a (which is installed at the suction point), and filter facility located on the existing road then returns it to the belt conveyor as puri- near the two-level sieve facility. It consists fied. Depending on the required amount of of two symmetrical lines that work in par- air for suction, 3 dedusters, manufactured allel. Each line consists of a bag filter with by KDK-EKO, with the following charac- air blowing under which there is a pyram- teristics were selected: idal steel bunker for dust collecting with - Designation: KFE-12-TV/2-R the associated equipment. Technical char- - Filter area15 m2 acteristics of the filter are as follows: - Capacity: 1260 m3/h Type: HVP bag filter with involute inlet - Power: 4 kW Producer: CAMCORP - Designation: KFE-16-TV/2-R Designation: 8HVP504 2 2 - Filter area: 20 m Filter area: 453,274 m - Capacity: 1700 m3/h Filter capacity: 33450m3/h - Power: 4 kW Dimensions: 4267,2x12911mm Total mass: 9915 kg - Designation: KFE-24-TV/2-R 2 From the fan, the purified air is ejected - Filter area: 30 m 3 into the atmosphere through the exhaust - Capacity: 2520 m /h element with a protective net. On this sec- - Power: 5 kW tion, a connection for measuring and sam- pling dimensions is provided, and in its 3.1 Calculation vicinity, the same connection is also provided on the incoming pipeline of dusty The following calculation formulas air on the section. The choice of a fan with were used in the aerodynamic [6] calcula- a frequency regulator enables a relaxed tion of the pressure drop: start when starting the fan, easier regula- √ [ ] - diameter of a pipe- tion of the plant as well as the possibility for more flexible operation of the plant. line section (equivalent diameter) Dust separated in the filters is first collec- – friction coefficient ted in the conical lower part of the filter.

A level measuring device for signaling the √ [ ] - critical air maximum level as protection against over- filling will be mounted on the wall of the speed

No. 3-4, 2020 64 Mining & Metallurgy Engineering Bor

( ) [ ] - presure [ ] - gravitational constant drop in clean air flow [ ] - length of a pipeline section

- pressure increase [ ] - sum of the coefficients of local

resistance of a pipeline section factor [ ] - inclination angle of a pipeline sec- ( )[ ] – pressure tion drop during dusty air flow [ ] za - coefficient of Individual labels in formulas have the pressure increase following meanings:

[ ] za - coeffi- [ ] - air speed cient of pressure increase

[ ] - volume air flow The total pressure drop includes the

additional pressure drops in the appropri-

[ ] - concentration of solid parti- ate sections, as follows: [ ] cles in the air 1. - underpressure in suction hoods

[ ] - density of solid parti- 2. [ ] - pressure drop in cles a bag filter with pulse shaking

Calculation of the pressure drop in a [ ] - air density pipeline for the most unfavorable circuit is given in the table.

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4 CONCLUSION

If the problem of spreading the air pollu- проектированию санитарно-техни- tants would be solved where it is regenerat- ческих устройств основных цехов и ed, then it would be a significant contribu- отделений заводов огнеупоров СН tion to the preservation of the human envi- 155-61», Москва, 1961 ronment. The importance of clean, unpollut- [4] ОНТП-10-85 Минстройматериалов ed air in the industrial zones is well known. СССР: «Общесоюзные нормы Well-designed and executed ventilation of- технологического проектирования fers a solution that will bring the air pollu- предприятий по производству tants at least below the maximum allowable извести» concentrations, and thus provide the neces- [5] Волков Олег Димитриевич: sary protection for workers in such condi- «Проектирование вентиляции tions. This paper gives a practical solution to промышленного здания», Харьков, the problem related to the appearance of 1989 increased dust concentration at the suction points in the plant for limestone preparation [6] M. Bogner, D. Vuković: Problems Zagradje-5. from Mechanical and Hydro- Figure 1 defines an optimal layout of air mechanical Operations, Faculty of purification equipment. Air purification Mechanical Engineering, Belgrade, equipment can be installed in other ways 1991 (in Serbian) depending on the specific conditions. [7] Supplementary Mining Project for Excavation and Preparation of REFERENCES Limestone in the Deposit "Zagradje- 5", Mining and Metallurgy Institute, [1] Приложение N°11к Приказу Bor, 2020 (in Serbian) Министра охраны окружающей [8] Standard SRPS Z.B0.001-1991 среды Республики Казахстан от 18 entitled "Maximum Permissible 04 2008 года N°100-п: «Методика Concentrations of Harmful Gases, расчёта выбросов загрязняющих Vapors and Aerosols in the веществ в атмосферу от пред- Atmosphere of Work Premises and приятий по производству строи- Construction Sites" ("Official Gazette тельных материалов» of SFRY", No. 54/91) [2] Борис Семенович Молчанов: [9] Decree on Limit Values for Emissions «Проектирование промышленной of Pollutants into the Air from the вентиляции», Стройиздат, Ленин- Stationary Pollution Sources, Except град, 1970 for Combustion Plants ("Official [3] Государственный Комитет Совета Gazette of RS", No. 111/2015) Министров СССР по делам строительства: «Указания по

No. 3-4, 2020 66 Mining & Metallurgy Engineering Bor MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 681.325:622.271.2(045)=111 DOI: 10.5937/mmeb2004067B

Dejan Bugarin*, Ivan Jelić*, Miljan Gomilanović*, Aleksandar Doderović*

APPLICATION OF THE COMFAR III SOFTWARE PACKAGE IN DEVELOPMENT A FEASIBILITY STUDY OF INVESTMENT ON AN EXAMPLE OF TECHNICAL-CONSTRUCTION STONE OF THE OPEN PIT GELJA LJUT**

Abstract

This work presents the application of the COMFAR III software package in development a feasibility study of investment. The application of this program enables an efficient analysis of investment justification and numerous variations of both input and graphic and alphanumeric output data. The methodological basis of economic analysis, used in this software package, is based on decades of experience of economists, engineers, managers, ecologists and experts from the other fields, as well as on the experience of numerous investment projects within the United Nations Industrial Development Organization. The applied methodology is the current standard in the field of economic evaluation and analysis of the industrial development projects. The software package was used on a specific example of the open pit of technical stone Gelja Ljut-Gacko, in a function of providing the concession right of this deposit for the needs of the Gacko Mine and Thermal Power Plant. Keywords: Investment Feasibility Study, COMFAR III, investments, costs, techno-economic assessment

1 INTRODUCTION

The Mine and Thermal Power Plant Plant Gacko performs a number of activities Gacko a.d. Gacko is a subsidiary that oper- in the function of stable, reliable and eco- ates within the Mixed Holding "Elektro- nomically efficient production. The com- privreda Republike Srpske", Trebinje. The plexity of production process, the number main activity is the production of thermoe- and variety of activities and influential fac- lectric energy, and the other special activities tors that are one of the basic characteristics are lignite mining at the open pit, quality of production within the Mine and Thermal improvement, transport and storage, quarry- Power Plant Gacko [1]. In the set of activi- ing, crushing and breaking of construction ties related to the surface exploitation of stone, chalk and limestone, machine repair, lignite and technological processes of exca- electrical equipment repair and sale of elec- vation and exploitation of coal, there are tricity to the customers. significant needs for the technical- In order to realize its basic goal, to en- construction stone of appropriate quality sure the production of planned amount of within the preparatory and auxiliary electricity, the Mine and Thermal Power works.

* Mining and Metallurgy Institute Bor ** This work is financially supported by the Ministry of Education, Science and Technological Develop- ment of the Republic of Serbia, Agreement on the realization and financing of scientific research work in 2020 for the Mining and Metallurgy Institute Bor, no. 451-03-68 / 2020-14 / 200052.

No. 3-4, 2020 67 Mining & Metallurgy Engineering Bor In the process of exploitation, tech- open pit Gacko - Centralno polje. In addi- nical stone is regularly used for the needs tion to this, a road and pipeline are located of maintenance the transport and access in the immediate vicinity, the infrastructure roads [2], various embankments, construc- facilities that are maintained and exploited tion of plateaus, drainage filling, construc- by the Mine and Thermal Power Plant tion of protective barriers and embank- Gacko. ments for the purpose of improving the As a basis for the future business deci- bearing capacity and stabilization of soil sion, the management of the Mine and and slopes as well as the other purposes. Thermal Power Plant Gacko required a de- In addition to this, in the coming period, velopment of a Feasibility Study for in- there is a significant additional need for vestment in providing the concession right technical stone in order to regulate the at the Gelja Ljut deposit with a comparative flow of the river Musnica (Phase II) and economic analysis of providing the tech- construction the infrastructure facilities nical stone from the Ponikve location. The that accompany mining at the open pit. main goal of this study was to determine the The need for this type of material is var- economic parameters of investment in iable and is mainly in the function of dy- providing, purchase, a concession right for namics the development of coal mining exploitation of limestone for the needs of works. Based on previous experiences, the the Mine and Thermal Power Plant Gacko annual need for limestone as a technical- at the Gelja Ljut deposit in order to make an construction stone of about 30,000 čm3 has investment decision. been estimated. For the construction of in- In order to make this assessment of the frastructure facilities in 2020 and 2021, it is Project success as objective as possible, in necessary to provide significantly larger addition to the economic assessment of quantities of limestone and they are estimat- providing the concession in question, the ed at an additional about 70,000 čm3. In the other important factors were also consi- previous period, the needs for technical dered, such as the possibility of using this stone the Mine were mainly provided from space to form an external landfill of the the open pit Ponikve, which also belongs to Gacko - Centralno open pit and other forms the Mine and TPP Gacko. of this area usage, and also an assessment Considering the dislocation of the sur- was given for possible legal, technical and face mine Ponikve in relation to the open pit environmental risks both in the case of of lignite, there was a need for analysis the providing a concession and in the case of provision of technical stone from the other maintaining the existing situation [3]. The sources as well. The Gelja Ljut limestone techno-economic assessment also includes deposit has been identified as one of the the results of a comparative analysis of possible sources of supply with technical- limestone providing from the existing open construction stone. pit Ponikve and the open pit Gelja Ljut. The area of concession right for exploi- When providing the technical stone, it tation the technical construction stone - was necessary to keep in mind some special limestone at the location of Gelja Ljut bor- requirements, which differ from the usual ders the concession area of the open pit system of providing technical stone for the Gacko - Centralno polje in its southwestern market. In the first place, there is a high va- part. The subject concession area is in the riability in the need for technical stone at the immediate vicinity of the regulated course open pit. Requirements can often be urgent of the river Mušnica and the zone of influe- and high capacities are needed only for a nce the designed works on the external dis- limited time. In the periods of construction posal of overburden and waste from the the important infrastructure facilities, it is

No. 3-4, 2020 68 Mining & Metallurgy Engineering Bor necessary to provide the quantities that ex- - providing a raw material base for the ceed the capacity of the open pit many production of technical stone, times, and these requirements are expressed - providing adequate quantities of in the periods related to the construction of technical stone dynamically, capaci- the facilities themselves, i.e. they do not tively and qualitatively in accordance have a permanent character. with the needs of the Mine and the Also, the special purpose of purchasing Thermal Power Plant, a concession at the Gelja Ljut site is to pre- - unification of concession areas in or- vent the occurrence of conflicts of interest der to prevent conflicts of interest in two neighboring concession areas. As and use of the concession area of the both spaces are in the zone of influence of Gelja Ljut deposit for formation an the other, it is possible for them to appear, external landfill of the Gacko - and in the recent past there have been such Centralno polje open pit. cases when the interests of the owners of both exploitation fields are inconsistent. So 2 THE OPEN PIT GELJA LJUT far, this has not affected the works on coal exploitation at the open pit Gacko - Cen- On the territory of the municipality of tralno polje in a way that would prevent the Gacko, as a distinctly limestone area, two realization of planned works, but such a concessions are currently issued for the scenario is known in the future considering exploitation of technical-construction stone the formation of an external landfill next to - limestone. There are two limestone quar- the concession area of Gelja Ljut. ries - Ponikve and Gelja Ljut. The position Based on the above given, three main of the concession boundaries is shown in purposes of financing have been identified Figure 1. as follows:

Figure 1 Position of the concession area of the limestone deposit as a construction-technical stone Ponikve (1) and Gelja Ljut (2)

The Gelja Ljut deposit is located on Gacko - Centralno polje is planned along the southern edge of the Gatačko field. the entire Gatacko field, the deposit is Since the development of the open pit located on the south side of the future con

No. 3-4, 2020 69 Mining & Metallurgy Engineering Bor tour [4]. The altitude of the deposit area within the exploitation field bounded by generally ranges between 930 and 970 m the coordinates of the breakpoints shown above sea level. The deposit is defined in Table 1 and Figure 2.

Table 1 Coordinates of the breaking points of the boundaries of exploitation field of the deposit of construction stone - limestone "Gelja Ljut" near Gacko Coordinates of points Point X Y A 4,777,264 6,541,716 B 4,777,415 6,541,716 C 4,777,520 6,541,815 D 4,777,510 6,542,245 E 4,777,105 6,542,245 F 4,777,105 6,542,143 G 4,777,190 6,542,850 A 4,777,264 6,541,716

Figure 2 Position of the exploitation field Gelja Ljut

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The open pit Gelja Ljut was opened in lysis can be performed using various as- th the 80s of the 20 century. During its exist- sumptions regarding the inflation, currency ence, the open pit changed several owners, revaluation and price escalation. while the production was carried out on a COMFAR III Expert is available for MS larger or smaller scale, with longer or short- Windows 98 / ME and MS Windows 2000 / er interruptions. The mine is about 15 km KSP / 2003 / Vista. away from the settlement of Gacko, while it After determining the type of project in is 3.6 km away from the open pit Gacko- the program (industrial, agro-industrial, Centralno polje. Until the moment when the infrastructural, tourism, mining or environ- works on coal exploitation in the roof coal mental) and the level of analysis (feasibility series cut the road to the village of Kula, the or feasibility study), the user is guided distance from Gacko was 4 km. through the data entry, data structuring, calculations, display and printing of results 3 COMFAR III and charts. COMFAR III Expert allows users a For the calculation of economic parame- flexibility in determining the detailed analy- ters, the COMFAR software package, sis. The main features are: [5] formed by the United Nations Industrial - new option or expansion / rehabilita- Development Organization (UNDO), and in tion project cooperation with the governments, business - joint venture option associations and individual companies en- - CDM / JI project option (Kyoto Proto- gaged in solving the industrial problems, col) was used. COMFAR, in essence, is a tool - variable planning horizon - up to 60 for forming a computer model for feasibility years analysis and reporting. The main module of - variable time structure: construction program accepts the financial and economic and start-up - up to 20 products can be listed data, prepares the financial and economic - data can be entered in up to 20 curren- reports and graphical representations and cies calculates the performance measures. The - direct cost option additional modules help in the analytical - escalation / inflation option process. - economic analysis option The methods of economic analysis de- The standard structure of investment veloped by the UNIDO and costs and bene- costs, operating and marketing costs is ex- fits of added value are included in the pro- tended to the entry of subchapters. Sources gram, taking into account the methods used of financing include the capital, long-term by the major international development loans, short-term finance and defining the institutions. The program is applicable for terms of profit distribution (Figure 3). an analysis of investments into the new pro- With these facilities, the COMFAR III jects and expansion or rehabilitation of the Expert can be applied to all types of in- existing companies, e.g. in the case of pri- vestment projects, investments with the vatization projects. For joint ventures, the medium-sized companies, to the analysis financial perspective of each partner or class of large projects or complex production of shareholders can be developed. The ana- units.

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Figure 3 Data structure within the software

COMFAR III Expert - Cash flow model: Financial analysis: The COMFAR system distinguishes the The COMFAR III Expert, based on the cash flows in domestic and foreign currency, entered data, provides the following in- and at the same time requires changes in the formation in Table with data, investment exchange rates. A number of standard func- costs. production costs, production and tions are available for calculating the net sales program. Sources of financing and working capital, debt, annual depreciation of repayment, business results (financial cash fixed assets and income tax. From different flow, discounted cash flow, income state- areas of finance and efficiency, the benefi- ment, balance sheet, data on direct costs ciary can select those data needed to evalu- and product profitability - Figure 4). ate the project. Direct prices, allocation of indirect costs to profit centers and analysis in constant or current prices are also available.

Figure 4 Example of cash flow

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Economic analysis (macro level):

The economic analysis option allows of return (Figure 5), value added, foreign the user to enter the approximate (ex- exchange effects and effects on employ- pected, assumed) prices (to express inputs ment. All results can be calculated, inclu- and project results in terms of economic ding and excluding the external economic prices) and to calculate the economic rates effects.

Figure 5 Form of the program with presentation the results of economic analysis

The COMFAR III Expert provides the as the structure of cash flows, costs and user with an overview of possibilities of revenues (Figure 6). the average graphic presentation, as well

Figure 6 An example of output graph

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Sensitivity analysis:

Using the sensitivity analysis, it is possi- bles. Different graphs are available to ana- ble to show how net cash returns or invest- lyze the structure of input and output pro- ment profitability change with different va- jects, e.g. the structure of annual production lues assigned to the variables needed for and sales program, or variable and operating calculation (sales prices, unit costs, sales margins as well as the unequal sales vo- volume, etc.). The COMFAR III expert fa- lumes. The COMFAR III offers an additio- cilitates the assessment of alternative project nal analysis to facilitate the calculation of scenarios and identification of critical varia- impact the project extensions or remediation.

Figure 7 An example of sensitivity analysis

4 CALCULATION RESULTS USING THE COMFAR III SOFTWARE PACKAGE 4.1. Calculation and dynamics of income and expenses

Input data for the needs of economic assessment of the value of existing facili- analysis were obtained within the tech- ties and equipment. nical part of consideration the exploitation The total revenues from the open pit of technical stone from this deposit. They Gelja Ljut refer to the sale, i.e. placement included both capital and operating costs of technical stone aggregates for the needs of exploitation. In this part of the activity, of the Gacko Mine and Thermal Power Plant, and infrastructure facilities that are the participation of experts from the field being constructed for the needs of the of mining is necessary in order to define mine. The annual product placement as the appropriate technical solutions, but the well as its dynamics, revenue dynamics experts from other fields such as mechani- and calculation are presented in the form cal engineering, electrical engineering and of an output form of the COMFAR III construction, in order to give a realistic software package (Figure 8).

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Figure 8 Detail of an output form of the COMFAR 3 software package with dynamics and revenue calculation

The total costs of production of lime- - investment costs, and stone and aggregates at the open pit Gelja - other expenses. Ljut included: The annual cost amounts as well as its - costs of standardized material, dynamics are presented in the form of an - processing costs, output form of the COMFAR III software - labor costs, package (Figure 9). - maintenance costs,

Figure 9 Detail of an output form of the COMFAR III software package with operating and investment costs

4.2 Financial flow

In order to analyze in more detail the sis and measurement of the effects obtained possibilities of evaluating the efficiency, i.e. from one investment project. [6] The mea- the justification of realization of invest- surement of effects brought by an investments, it is necessary to enter into the analy- ment project is done by calculating the cer-

No. 3-4, 2020 75 Mining & Metallurgy Engineering Bor tain indicators or criteria that express the includes an assessment the profitability and effects of respective investment project. The liquidity of the project. The financial flow of financial evaluation includes consideration the project is given in the form of an output the effects of the investment project that the form of the program package (Figure 10). Investor has. The financial evaluation All values are given in euros.

Figure 10 Detail of an output form of the COMFAR III software package with financial flow

4.3 Economic flow

For a successful evaluation of invest- the return expected from investment in the ment projects, it is necessary to take into project. In this Study, a discount rate of account the preferences of time, i.e. to 12% was adopted and it is significantly apply a discount account that reduces the higher than the currently valid interest rate series of future amounts to the present on loans with a currency clause of the Central Bank of Bosnia and Herzegovina, value. The basis of a discount account is a which amount to 3.139% for 2020. discount rate. In general, the discount rate A significantly higher discount rate is is the interest rate at which the central a measure of expectations of the Project bank gives liquidity loans to the commer- success from community. The economic cial banks, but it is more often linked to flow of the project was calculated for a the process of discounting and measuring discount rate of 12% and is presented in the time value of money. In this particular the form of an output form of the COM- case, the adopted discount rate represents FAR III software package (Figure 11).

Figure 11 Detail of an output form of the software package - Economic flow

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4.4 Profitability

Profitability is the ratio of difference be- given in the form of an output form of the tween the total profit and total costs to the software package (Figure 12). total profit. The amount of Profitability is

Figure 12 Detail of an output form of the COMFAR software package with profitability expressed in %

4.5 Evaluation of financial efficiency

The results presented in the illustrated come, expenditure and periodic results. financial flow, shown in the previous ta- The dominant structural share of exploita- bles, clearly show the structural share of tion costs is 26% and earnings of 23% globally individual components of in (Figure 13).

exploitation costs

processing costs

maintenance and insurance costs depreciation costs

Figure 13 Cost structure

4.6 Variation of investments by the sensitivity analysis and investment risk

Sensitivity analysis was performed by 2. Investments - costs of providing the changing the following parameters concession right (increase of fixed 1. Sales prices (Revenues from sales) assets), and

No. 3-4, 2020 77 Mining & Metallurgy Engineering Bor 3. Costs of production and processing of limestone (Operating costs)

Figure 14 Output form of the COMFAR 3 software package with sensitivity diagram Table 2 Project sensitivity (%) Change (%) Sales revenues Increase in fixed assets Operating expenses -20.00 % 4.97% 16.77% 17.31% -16.00 % 6.36% 15.71% 16.29% -12.00 % 7.78% 14.74% 15.27% -8.00 % 9.25% 13.86% 14.27% -4.00 % 10.75% 13.04% 13.27% 0.00 % 12.29% 12.29% 12.29% 4.00 % 13.87% 11.59% 11.32% 8.00 % 15.49% 10.94% 10.36% 12.00 % 17.15% 10.33% 9.40% 16.00 % 18.86% 9.75% 8.46% 20.00 % 20.60% 9.21% 7.54%

Based on the presented values, it can ject to the value of input values, the indica- be concluded that the Project is the least tors of project economy for different values sensitive to the changes in investments, of investments in providing the concession and the most sensitive to the changes in right were especially considered. The results selling price of products. of the analysis are shown in Table 3 and In addition to the sensitivity of the pro- Figure 15.

Table 3 Cost-effectiveness indicators for a variable amount of investment Internal rate of Time of return Net present value of Investments (€) return (%) (years) the Project (€) 1,250,000 22.03 3.8 628,963 1,500,000 17.45 5.34 430,118 1,750,000 14.42 6.88 231,273 2,000,000 12.29 8.41 22,428 2,040,000 12 8.66 0

No. 3-4, 2020 78 Mining & Metallurgy Engineering Bor

Figure 15 Diagrams of IRR (%), time of investment return (%) and NPV of the project (€) as a function of investment amount

5 CONCLUSION

Based on the calculated economic pa- All financial and economic parameters rameters, the provision of the concession are positive. right for exploitation of limestone as a con- The static value of the project is € struction-technical stone on the Gelja Ljut 401,320, while the net present value of the deposit, under the conditions presented in project is for a period of about 14 years. This this Study, can be assessed as economically net present value of the project is a conse- viable and socially favorable. quence of strict conditions under which the The applied methodology of economic budget of economic indicators is calculated, evaluation implied an economic analysis a discount rate of 12% and maximized oper- taking into account the time factor and is ating costs with limited capacity to the part fully in accordance with the methodology that represents the direct needs of the Mine recommended by the United Nations Indus- and Thermal Power Plant for this mineral trial Development Organization (UNDO). resource and its products.

No. 3-4, 2020 79 Mining & Metallurgy Engineering Bor The social effects of the Project ex- Level for Mining at the Open Pit pressed through the ecological and general Gacko, Mining and Metallurgy Engi- conditions of closure in the conditions of neering Bor No.1-2 2017. taking over the concession right on the Gelja [4] N. Stanić, S. Stepanović, D. Gove- Ljut deposit are positive. darica, A. Doderović, Application the Software Solution for Calculation the REFERENCES Capacity of Bucket Wheel Excavators in the Complex Conditions from the [1] N. Stanić, A. Doderović, S. Stepa- Aspect of Resistance to Excavation, nović, M. Gomilanović, Dynamics of Mining and Metallurgy Engineering Development the Works of Roof Coal Bor No.3-4 2017. Series of the Open Pit Gacko by the [5] COMFAR III EXPERT – Software for Software Gemcom Gems - Module Project Appraisal and Analysis, United Cut Evaluation, Mining and Meta- Nations Industrial Development llurgy Engineering Bor No. 4 2016. Organization, Programme Develop- [2] N. Stanić, S. Stepanović, D. Bugarin, ment and Technical Cooperation M. Gomilanović, Selection the Division, Investment and Technology Rational Model of Transport Truck by Promotion Branch, Vienna, 2009. the Selective Coal Mining at the Open [6] Prof. Dr P. Jovanović, Investment Pit Gacko, Mining and Metallurgy Management, Faculty of Organiza- Engineering Bor No.1-2 2017. tional Sciences, Belgrade, 2006 (in [3] S. Stepanović, N. Stanić, M. Šešlija, Serbian) M. Gomilanović, Analysis of Coal Quality in a Function of Selection

No. 3-4, 2020 80 Mining & Metallurgy Engineering Bor MINING AND METALLURGY INSTITUTE BOR ISSN: 2334-8836 (Štampano izdanje) UDK: 622 ISSN: 2406-1395 (Online)

UDK: 336.7(045)=111 DOI: 10.5937/mmeb2004081M

Nemanja Matić*, Boris Siljković**, Marko Savić**

POTENTIALS OF TRADITIONAL CASH METAL COINS VERSUS DIGITAL CONTACTLESS PAYMENT IN THE TIME OF CORONAVIRUS PANDEMIC

Abstract

This paper addresses the challenges associated to the strength of potential for payment with traditional metal cash and paper money versus a non-cash method of payment in the era of the COVID 19 pandemic in the world and our country. The pandemic served to accelerate the contactless method of payment, because payment without contact is now not only a convenience, but a necessity. Before the pandemic in Europe, cash accounted for close to half of the payments, and in just a few weeks of the COVID 19 pandemic, it fell by 10 percent. Concepts that have so far preferred cash were definitely compromised during the pandemic crisis, and the pandemic is actually the strongest marketing of digital contactless payment methods so far, through the dominant contactless style of money exchange in the world and Europe, as shown in the paper we have today. Some research studies described in the paper in form of the health adventages of mobile wallet payments, as opposed to the proven health-threatening cash and coin-based cash payment model, indicate that the end of the cash era is approaching, being primarily accelerated by the health risk of COVID 19 infection. Particularly interesting is the live study conducted in the area of the northern Kosovo and Metohija, presented in a form of a set of financial services offered by the Postal Savings Bank of the Kosovska Mitrovica branch office, and relation between the contactless and cash payment model, before and after the COVID 19 pandemic. Naturally, all of this is accompanied by significantly limited knowledge related to SARS Cov 2, better known as the current COVID 19 pandemic. Keywords: paper money, metal money, cash, contactless payment, COVID 19, pandemic

1 INTRODUCTION

The coronavirus pandemic of 2020 channel for delivery of most banking promoted digital mobile, network and transactions, the job was made easier both contactless payment, which means that for banks and customers. Khalek and there are few arguments against applica- Bakri [1] Telephone, Internet and mobile tion of this model in the post-pandemic phone have become the main channels of period. E-banking involves delivery of digital banking services making them im- banking products and services through the portant for the survival of banks, due to electronic channels that had been previ- their advantages and practicalities, any- ously done through telephone transactions time and anywhere. Sundarraj and Wu, and automatic teller machines (ATMs). 2005; [2], Daniel, 1999; [3], Mols, 2001. Later, with the Internet application, which [4] During and after the corona virus pan- was considered as the fastest and best demic, the banking world, along with the

* Delikos DOO Sopot, [email protected] ** Academy of Applied Studies, Department Peć-Leposavić, [email protected], [email protected]

No. 3-4, 2020 81 Mining & Metallurgy Engineering Bor

2 HEALTH POTENTIAL OF DIGITAL AND CASH EXCHANGE OF MONEY IN THE AGE OF THE COVID PANDEMIC 19 ecologically contactless payment every- The time of pandemic has indicated where in the world, should become abso- that we have an adaptable so-called a lute priority. This payment model will coronavirus environmental bank that has almost certainly be present for a long time an updated model of digital services in- even after the coronavirus pandemic. The cluding a health strategy of contactless coronavirus pandemic will definitely payment methods. The BRIC countries, change everything that was once the norm specifically the Government of India will of traditional banking financial services, perform all payments in the futuristic especially the cash payment method and world using the contactless cards, mobile the digital payment method. Digital con- phone applications and other electronic tactless banking enables the development means, while the banknotes and coins will of customer services, reducing the costs be abolished. [7] associated to face-to-face transactions Contactless payment was already on with customers in branch offices. Dootson the rise in the U.S.A, but the ongoing et al., 2016. [5] coronavirus pandemic has increased the The model of traditional banking is be- number of Americans using a variety of ing tested during this coronavirus pande- non-contact payment methods. mic and it has been shown that the tradi- In the US, more than 51% of people tional cash payment model is currently have opted to use so-called mobile wal- outdated. The European Central Bank lets, such as the Apple Pay and other Tap- To-Go credit cards. Consumers mainly surveys conducted in June 2020 showed a use the contactless cards to buy necessi- sharp decline in the share of cash pay- ties, namely: food: 85%, pharmacy: 39%, ments during the first lockdown of eco- retail: 38% fast food restaurants (KSR), nomies across Europe where consumers fast food: 36%. [8]. pay in cash, but much less than before the Table 1 actually shows the reasons pandemic. why the health benefits of digital payment Knowledge and people who know how in the COVID 19 pandemic era have pre- to apply that knowledge participate in the vailed over the traditional cash and paper development of society nowadays. [23] money payments. This has primarily allowed the electronic China, where coronavirus COVID 19 contactless banking, which represents the or Sars Cov 2 first appeared, and its Chi- application of the new/old technological nese National Health Commission have solutions, and has made possible to the classified the new coronavirus as a class A infectious disease, requiring the strictest users to perform the money transactions preventive and control measures, inclu- from anywhere and at any time they want ding mandatory patient quarantine and using the computer networks. Ilić et al., treatment of those who were in a close 2015 [6] contact with them [19].

No. 3-4, 2020 82 Mining & Metallurgy Engineering Bor

Table 1 Health potential of using the digital contactless payment versus use of metal and paper money It is moderately contagious and depends on the composition of the money alloy, its production is Use of metal coins more expensive, up to two times of nominal value, and it is harder to protect against counterfeiting. Contagious for several days, cheaper to make than Use of paper money coins and easier to protect against a counterfeiting

than coins. Less contagious if contactless, does not change the Use of contactless card, Master and owners and does not come into contact with sellers Visa card. In the USA, cards of the and traders. A plastic card costs less than paper present and the future money and coins, because it can be used longer — (Visa Inc., Mastercard Inc., American commercial moment. Payment cards have eliminat- Express Co., PayPal Holdings Inc.) ed the need to carry money while reducing the chances of theft or loss of currency. Mobile applications for payment E The least contagious with the use of hygienic clean- banking, Home banking and M banking products for the phone. It requires a mobile ing, so-called digital wallets phone or computer and an Internet connection. Cardboard The virus remains on it for 24 hours. [9] Research 1: Materials on which germs and viruses can be minimum kept: Sars Cov 1 and SARS Cov 2 - 5.6 hours on stainless steel and 6.8 hours on Stainless steel (banknotes) and plastic plastic. Although the extent of the virus has been cards significantly reduced, this virus is more stable. Research 2: Even after 72 hours, SARS Cov 2 could be found on plastic and 48 hours on stainless steel [10] Solid surfaces and materials e.g. ATMs Sars Cov 2 virus can stay alive for up to two days and POS terminals [11] SARS-CoV 2 or Covid 19 virus remain present for 4 hours. It has been proved that copper-containing surfaces show antiviral activity as opposed to pol- ymer surfaces used to make paper banknotes, where the virus could survive for several days. [12] Cop- Copper alloy for money banknotes per deficiency, although rare, makes people more susceptible to infection. [11] The continuously self- sterilizing form of copper is 99% capable of deac- tivating SARS-CoV-2 or COVID 19 in 30 seconds. [12] Analysis of 22 studies reveals that the human coronaviruses such as the Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syn- Metal and glass drome (MERS) or Endemic Human Coronaviruses (HCoV) can persist on inanimate surfaces such as metal, glass or plastic for up to 9 days. [13]

No. 3-4, 2020 83 Mining & Metallurgy Engineering Bor

3 PRIMATE OF DIGITAL MONEY EXCHANGE AS THE MAIN STYLE IN THE AGE OF THE COVID 19 PANDEMIC IN THE WORLD WITH REFERENCE TO SERBIA

If we use the research and online sur- llets and the second market with the fast- vey of Accenture NYCE: in 20 countries est growth of payments in the world. In with 120 bank directors during the pan- Germany, more than half of card pay- demic from July to August 2020 as shown ments in the year of the pandemic were in Figure 1 below, it can be seen that the contactless, compared to 35% before the biggest payment disruption was in the economy was hit by the coronavirus crisis. USA, followed by the UK, because the Since June 2020 in the Netherlands, con- consumers have been opting for the new sumers have paid 20% in cash at their digital payment methods. The surveyed points of sale. This is significantly lower markets include: Australia, Brazil, Cana- than in January and February 2020, when da, China, Denmark, Finland, France, 30% of their purchases were paid for in Germany, India, Italy, Japan, the Nether- cash, but more than immediately after the lands, Norway and Singapore. In China, outbreak of COVID 19. In the Netherlands for instance, the mobile wallets are rapidly in April 2020, only 15% of purchases were taking precedence over cash payments - paid for in cash. In October 2020, the con- 76% of transactions in 2019 come from sumers used the contactless payment meth- mobile wallets, compared to 12% in 2014. ods for 67% of their purchases at points of For several years now, the consumers in sale, compared to only 50% at the beginning China have been accustomed to use the of the year. As it can be seen in Figure 1, the mobile applications and QR codes to pay contactless payment in the Netherlands has in restaurants and stores. Even before the increased to the detriment of cash payments, pandemic, China was the second in the and in particular pin-code mobile payment - global share of payments by mobile wa- QR telephone code payment. [22]

Figure 1 Choice of payment instruments in the Netherlands at points of sale [22]

No. 3-4, 2020 84 Mining & Metallurgy Engineering Bor If we look in Figure 2 in the UK in a for contactless payment will be in markets pandemic year, the "tap and pay" model such as Southeast Asia and Latin America, makes up more than 40% of card payments. where a cash consumption dominated, and, In mature markets - such as Western Europe, in some regions, has even increased during payments are mostly commodified - only the pandemic. The size of a circle in Figure gradual changes are expected to be seen 2 indicates the relative value of transactions through purchases. The greatest opportunity in each country. [14] [22] [15]

Figure 2 Increase of digital payments during the COVID 19 pandemic worldwide [14]

Almost all users of smartphone ser- in India, Denmark, Sweden and South Ko- vices will be in the Asia-Pacific region rea. The information in Figure 3 presents an and mainly in China, which will make up overview of the global proximity payment the majority of the world's users of direct environment through the mobile applica- mobile payments. Mobile payments are tions, including adoption trends in major also popular among the smartphone users markets and key players.

Figure 3 Predictions of payment services via mobile applications in the world 2018-2023 [16]

No. 3-4, 2020 85 Mining & Metallurgy Engineering Bor

A strong cash payment culture is giving have performed at least one proximity mo- way to the non-cash payment methods main- bile payment transaction in the past six ly due to the COVID 19 pandemic and in months. Sincerily, in numerical terms, the order to prevent the spread of coronavirus. growth of people using mobile applications For instance, in 2020, there will be 59.3 mil- is predicted, and in percentage terms, there is lion mobile payment users in Western Eu- a noticeable decline in users of contactless rope, close to 18.7% more than in the previ- mobile payment services as we move away ous year. Stable growth is expected until from the base pandemic 2019 in Western 2023 through the number of service users, Europe, and Figure 4 directly proves it. [17] when 70.6 million people in the region will

Figure 4 Rise/fall in mobile phone payments 2019-2023 in the economies of Western Europe [17]

According to a research conducted by involved in e-m banking. We had intro- BuyShares.co.uk in June 2020, the global duced the mobile wallets in Serbia, and it mobile wallet industry is worth $ 1.47 was thought that everyone would immedi- trillion versus $ 405 billion in 2017. The ately pay exclusively by phone. Will the number of people choosing mobile wallets COVID 19 pandemic change that, and to manage their payments should jump indications show that it will continue in over 29.6% per year by the end of 2020. 2021, with long term consequences. How- The data reveals that China is the leading ever, the health progress is certain, but not player in the mobile wallet industry, and is visible enough for the time being, since predicted to reach a value of 50% of the the mass immunization just began in Jan- world’s overall market value in 2020. uary 2021. However, the statistics show that the Unit- When it comes to the wider use of mo- ed States, Great Britain and Brazil, as the bile wallets, it is still going slowly both in leading markets for mobile wallets, are Serbia and the region, cash is still used a expected to grow in 2020. [18] lot. What is being talked about and written Serbia is in the early stages of e- about everywhere is reaching the ordi- banking growth because just over a third nary people and wider population in the of the population is currently active or region and Serbia more slowly.

No. 3-4, 2020 86 Mining & Metallurgy Engineering Bor

4 LIMITATION / DIVERSITY OF PAYMENT METHODS - CASE STUDY POSTAL SAVINGS BANK - KOSOVO MITROVICA

Since the declaration of the state of method of payment and use of services in emergency in Serbia and the proclamation of the territory of the northern Kosovo and the COVID pandemic on March 19, 2020, Metohija. When it comes to the Posatal Sav- the Postal Savings Bank in Serbia with its ing Bank, it called on clients to use the elec- branch office in Kosovska Mitrovica has tronic banking services as much as possible, invited its clients to use the electronic bank- i.e., remote access to payment and payment ing services as much as possible, i.e., remote services in the conditions of the state of access to payment services and transactions. emergency in the country, declared to pre- Here, for our needs, and in order to deter- vent spreading of the Covid-19 virus. mine the factual situation in the area of the Due to these circumstances, we have fo- branch office of the Postal Savings Bank in cused on examining the provision of finan- Kosovska Mitrovica, we have made an anal- cial services of the Postal Savings Bank in ysis through an anonymous survey. For this the north of Kosovo and Metohija, which is purpose, we have made an overview of the registered as a service provider in Serbia, use of contactless versus cash payment and this bank in Kosovska Mitrovica was methods from the point of view of users- officially opened on April 1, 2018 and oper- clients and service providers on the example ates in the payment system of Serbia. of the Postal Savings Bank of Kosovska The conducted survey was of an anony- Mitrovica and its four municipalities through mous type, with 100 people of different ages the branche office in which they operate: from 25 to 65 and older participated, where Kosovska Mitrovica, Zvecan. Zubin Potok both sexes were equally represented. Time and Leposavic. period of the survey was March 2020 - Au- At the very beginning of the research, we gust 2020. We received the greatest number encountered a crucial limitation in form of of answers from the respondents of young impossibility of using electronic payment age 35-44, and middle age 45-54. Signifi- services in full capacity for the simple rea- cantly few participants were very young son of unavailability, i.e., relatively small aged 18-25 and mature over 65-70. number of POS terminals in retail stores, Persons with the high school and faculty restaurants, restaurants and other facilities. It degree were equally represented in the an- is noteworthy that there is still a lack of cul- swers. Very few people with primary school ture of electronic payment amongst the pop- and high academic degree of master and ulation of the northern Kosovo and Metohi- doctor of science participated. ja, although some progress in the use of Based on the answers to the questions electronic services is noticeable, especially asked, it was confirmed that cash withdrawal after the declaration of the pandemic and the is the dominant form of using the services of use of electronic payment methods. the Post Office in the north of Kosovo and Due to these facts, all types of electronic Metohija, with most clients. The survey has services, primarily payment cards and mo- shown that the younger population prefers bile applications offered by the Postal Sav- contactless payment methods mainly ings Bank of the Kosovska Mitrovica branch through mobile applications, but it is insuffi- office, have limited practical and application ciently/very little used. It is noteworthy that value. Therefore, the bank's client/consumer all categories of the surveyed population is prevented from using the so-called mobile agreed that the following types of electronic wallet and electronic services in full capacity payment payments are popular from the and is mostly oriented towards the cash health perspective: a). card, b). mobile appli-

No. 3-4, 2020 87 Mining & Metallurgy Engineering Bor cation, followed by c). check and e) cash. that paper for money printing may be less True, it may be stated that the respondents of contagious with the Coronavirus (Covid 19) all ages did not have an aversion for the use than banknotes. However, both this and pre- of cash as a method of payment and with- vious studies have shown that coins and drawal of cash during the current pandemic. banknotes can be highly transmissible and Due to these reasons related to the use of pathogenic. (Evidence - Table 1). Mobile cash and the respondents' answers that there phones and computers may be reservoirs of were no fears in terms of health security, a infection, primarily due to the material they new study from the USA in 2020, which are made of (glass, plastic and metal). This proves the opposite, is being analysed. In the is also confirmed by the research given in appendix below, Table 2 has provided suffi- the appendix in Table 2, where it has been cient evidence that there is contamination proven that SARS Cov 2 (Covid 19) lives with the COVID 19 virus (SARS Cov 2) and the longest on plastic and stainless steel.

Table 2 Sars Cov 2(Covid 19) lifespan on different materials [ 20] [ 21] Material Sars Cov 2(Covid 19) lifespan on different materials Measurements of 0 - 3 h, T ½ = 1.3 h Glass 3 h – 2 days, T1/2 = 4.8 hrs Measurements of Banknote 0 - 6 h, T1/2 = 0.9 h 6 h – 2 days, T1/2= 7.9 h 0 -30 min, T1/2 = 0.3 h Stainless steel 30 min – 4 days, T1/2= 14.7 h 0 - 6 h, T1/2 = 1.6 h Plastic 6 h - 4 days, T1/2= 11.4 hrs) 0 – 30 min= 4.76 h Paper 30 min - 2 days =1.18 h

Out of respondents who have an open interviews with employees of the Bank- mobile application, which mainly refers to Postal Savings Bank, the incrase of contact- the very young population aged 18-25, and less payment method has been observed, as recently the more mature population aged 35 opposed to the period before the pandemic. to 45 and over, only 1/3 of the respondents In order to support this claim, the evident mainly use it to pay for utilities, electricity, growth of e + m and home electronic ser- water, telephone and other charges. vices through the so-called mobile wallets of The dominant way of withdrawing cash the bank-postal savings bank can be used. by the respondents is from ATMs, while On the other hand, the number of counters of more than 1/3 of respondents decide to the Postal Savings Bank branch office in withdraw cash directly from the counters at Kosovska Mitrovica for cash withdrawals the post office and savings bank, as it is a does not support the affirmation of the con- case with: salaries, pensions, various social tactless method of payment, because it has benefits, payments for other person’s care, remained the same before and during the social assistance and other forms social be- COVID 19 pandemic. nefits. When using the financial services and If we analyze Table 3 in the package of payment methods, this research recorded a financial services of the Postal Savings Bank small number of POS terminals, e.g., many of the Kosovska Mitrovica Branch Office, small shops that are the dominant type of which are the unofficial information gath- retail, in the north of Kosovo and Metohija, ered by the authors of the paper through do not have the POS terminals.

No. 3-4, 2020 88 Mining & Metallurgy Engineering Bor In proportion to these technical limita- In order to distance the client from the tions, we note elements of insufficient or counter cash withdrawal method Bank in very low financial literacy of bank/postal favor of contactless payment, the management of the Postal Savings, the above- savings bank clients regarding the scope and mentioned financial institution raised the practical application of electronic services limit for ATMs cash withdraw from 20,000 using mobile applications. Political and se- dinars to 50,000 dinars and thus encouraged curity troubles in the north of Kosovo and this model of financial services during the Metohija also contribute to this state of COVID pandemic. modest and timid affirmation and spreading For this purpose of deterrence from the of contactless payment methods. cash method of payment, we have a certain A certain compensation should be percentage of commission for withdrawing mentioned here - a financial reason for not cash from the counters and ATMs, if you are or insufficiently using POS terminals, not a bank client, i.e. you do not have a bank both from the point of view of the bank's savings bank card. Data related to internet clients /bank users/ postal savings bank, payment were not available to us while the which limits this payment method in a so-called code telephone payment at this certain way. branch in Serbia is still in its infancy.

Table 3 Financial services package of the Postal Savings Bank of the Kosovska Mitrovica branch office*

Type of service / branch Branch office Zvečan Z. Potok Leposavić office K. Mitrovica-total Kind of financial services- Before during Before during Before during Before during payment method / branch pandemic pandemic pandemic pandemic office Number of counters 5 5 2 2 2 2 2 2 Number of ATMs 2 5 2 2 1 1 1 1 Number of cards 22,000 36,000 4,500 7,000 1,000 1,500 2,500 3,300 41 out of which K. Mitrovica Number of POS terminals 31 Before and 5 5 3 3 2 2 during pandemic e bank services for legal 2,400 9,600 700 3,800 1,200 6,400 300 1,700 entities-number e transaction m bank services + home services for individuals-number of 600 3,000 400 2,100 500 2,600 300 1,900 m and h transactions Internet payment - purpose defined visa No data No data No data No data -master card -electron visa QR payment-so-called tele- It is still developing in the north of Kosovo and Metohija and in Serbia phone. code payment * Note: The financial services package refers to the period shortly before the pandemic of March 2020 to December 2020. Source: Author's overview based on data collected through interviews and on information from the Postal Savings Bank of the Kosovska Mitrovica Branch Office

No. 3-4, 2020 89 Mining & Metallurgy Engineering Bor

Figure 5 Postal Savings Bank of the Kosovska Mitrovica

5 CONCLUSION

From the point of writing a paper on called commodity variety of payment met- contactless payment via cards, mobile wal- hods, especially in the so-called countries of lets and other models of electronic pay- the new Europe, Bulgaria and Romania. The ments, the need for cash has been forgotten. contactless payment model is still in its in- We have proven that by the use of contact- fancy, but also in development in the Bal- less payment, you pay from a secured, and kans region and Serbia. People pay more especially healthly safe distance, along with often by a card in Luxembourg and France. what the contactless method of payment The Scandinavian countries are at the very provides the most: speed, security, simplici- top of the scale. There, many hotels, bars or ty and convenience from any location. Re- shops do not want to accept payment with search conducted in the first two studies has coins and banknotes at all. In Sweden, 82% shown that the toxicity and transmissibility of people pay non-cash. We have shown in of SARS Cov 2 or COVID 19 in the use of the paper that the greatest opportunity for cash and paper money is great, but there are contactless payment will be in the future in also the other materials from which ATM markets such as Southeast Asia and Latin and POS terminals are made of, primarily America, where cash consumption dominat- due to metal, glass and plastic. It has been ed in the previous period. China, through the proven that, primarily due to these circum- form of contactless payment methods, has stances, mobile applications as a payment been dominating on a global level for many model are the most secure and thus the safest years, and with the pandemic, it has only method for the health aspect and the most confirmed its first place in the world in that practical from anywhere. Contactless pay- respect. Finally, it is evident that the growth ment is today, in time of the pandemic, the of e-commerce and payments is expanding, main style in all the economies of the world even more so during the COVID 19 pan- and Europe, which can be regarded as lead- demic. A practical live study in form of a ers, but there are exceptions. After all, survey and field interviews about the diver- COVID 19 only accelerated the "death" of sity/limitations of various modalities of fi- the cash method of payment in the devel- nancial services of the Postal Savings Bank oped Europe with the components of the so- of Kosovska Mitrovica, only showed a

No. 3-4, 2020 90 Mining & Metallurgy Engineering Bor growing trend of contactless payment meth- [6] Ilić, N. M., Spalević, Ž. and Veinović, od versus cash payment, with all the weak- Mladen. (november 2015). E - nesses and limitations that accompany the Banking Application and Security, development of various payment methods Conference: Sinergija, in Bijeljina, at this branch office. From a health point Bjeljina, Vol. 16 No. 1, pp.113 of view, this means that a trend or choice downloaded: of a safer payment model is growing, but https://www.researchgate.net/ that is still in its infancy. This only leaves publication/289525272_Elektronsko_b a question for some further research on ankarstvo_-Primena_i_Sigurnost, Date that topic in perspective. of access: 20/08/2020 [7] Samonagesh, V., Ganesh, S., M. REFERENCES Sathish, M. T. (Avgust-October 2020). Impact of Covid-19 Outbreak in [1] Khalek Y.A., and Bakri A. (November Digital Payments, International Journal 2017): The E Banking in Emerging for Innovative Research in Multi- Markets, International Journal of disciplinary Feld, Volume 6, Issue 8, Development Research, Vol 07, Issue pp.159 downloaded: (PDF) Impact of 11, pp.17186-17192, downloaded: Covid-19 Outbreak in Digital https://www.journalijdr.com/sites/ Payments (researchgate.net) Date of default/files/issue-pdf/11192.pdf Date access: 24/08/2020 of access: 20/05/2020 [8] https://www.cnbc.com/select/ [2] Sundarraj R.P and Wu J. (2005), mastercard-survey-contactless- “Using Information - Systems payments/ Constructs to Study Online - and Telephone-Banking Technologies”, [9] https://newsroom.ucla.edu/releases/ Electronic Commerce Research and covid-19-through-air-contaminated- Applications, Vol.4 No.4, pp.427-443. objects Date of access: 05/06/2020 [3] Daniel, E. (1999), “Provision of [10] Doremalen, V. N., Bushmaker, T., Electronic Banking in the UK and the Morris, H. D., Holbrook, G. M., Republic of Ireland”, International Gamble, A., Williamson, N. B. (March Journal of Bank Marketing, Vol.17 2017, 2020). Aerosol and Surface No.2, pp.72-82. Stability of SARS-CoV-2 as Compared with SARS-CoV-The New [4] Mols N.P. (2001), “Organizing for the England Journal of Medicine Effective Introduction of New downloaded: Distribution Channels in Retail Ban- https://www.nejm.org/doi/pdf/10.1056/ king”, European Journal of Marketing, NEJMc2004973, Date of access: Vol.35 No.5-6, pp.661-686. 24/04/2020 [5] Dootson, P., Beatson A. and Drennan, [11] https://www.newindianexpress.com J. (february 2016), “Financial /states/kerala/2020/mar/22/atms-pos- Institutions Using Social Media – Do machines-remain-hotspots-of-virus- Consumers Perceive Value?”, transmission-2120098.html, (Date of International Journal of Bank access: 10/08/2020) Marketing, Vol. 34 No.1, Emerald publishing, pp.9-36 [12] https://www.wunc.org/post/new- coronavirus-can-live-surfaces-2-3- days-heres-how-clean-them (Date of access: 05/04/2020)

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No. 3-4, 2020 92 Mining & Metallurgy Engineering Bor

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