Integration of Thermal Digital 3D Model and a MASW (Multichannel Analysis of Surface Wave) As a Means of Improving Monitoring of Spoil Tip Stability

E3S Web of Conferences 26, 00008 (2018) https://doi.org/10.1051/e3sconf/20182600008 2017 BGC

Integration of thermal digital 3D model and a MASW (Multichannel Analysis of Surface Wave) as a means of improving monitoring of spoil tip stability

Paulina Lewińska1,*, Rafał Matuła2, Artur Dyczko3

1 AGH University of Science and Technology, Faculty of Mining Surveying and Environmental Engineering, Krakow, Poland 2 AGH University of Science and Technology, Faculty of Drilling and Petroleum Engineering, Krakow, Poland 3 The Mineral and Energy Economy Research Institute of the Polish Academy of Sciences, Krakow, Poland

Abstract. Spoil tips are anthropogenic terrain structures built of leftover (coal) mining materials. They consist mostly of slate and sandstone or mudstone but also include coal and highly explosive coal dust. Coal soil tip fires cause an irreversible degradation to the environment. Government organizations notice the potential problem of spoil tip hazard and are looking for ways of fast monitoring of their temperature and inside structure. In order to test new monitoring methods an experimental was performed in the area of spoil tip of Lubelski Węgiel „Bogdanka” S.A. A survey consisted of creating a 3D discreet thermal model. This was done in order to look for potential fire areas. MASW (Multichannel analysis of surface wave) was done in order to find potential voids within the body of a tip. Existing data was digitalized and a 3D model of object’s outside and inside was produced. This article provides results of this survey and informs about advantages of such an approach.

1 Introduction source. Since there are usually a few sources of fire hidden inside and access to them limited stopping the fire may Spoil tips are anthropogenic terrain structures built of take years rather than weeks or days. Thus prolonging the unusable rock material excavated during underground or degradation of the environment [4]. open pit mining. Usually the term spoil tips refer to coal Spoil tips build currently are constructed in a way that spoil tip. As such they consist mostly of slate and various should mitigate or a least minimalize possibility of fires. types of sandstone or mudstone, also include coal and coal It is worth to mention that during past few years coal dust. Depending on the percentage amount of mentioned excavation in Poland has changed, becoming more and elements spoil tips can are susceptible to fires [5], [7]. more effective. Nowadays lower coal seams are being Coal tips fires could be caused externally or internally. excavated and there is much less leftover material External cause is relatively easy to eliminate – usually containing coal. Also more emphasis is put on localisation during construction and revegetation those structures are of spoil tips. They are being constructed, if possible, closed for public access or open only to some extent. further from human habitats and lakes, rivers, springs etc. However there are still a few that belonged to closed mines The latter being important due to the fact that internal fires and could be viewed as a constant treat. Most tip fires ware often fumed with oxygen coming from vaporising begin inside the structure. If a stack effect is introduced water. Rain water is being transported from the tip. Also within the body of the tip air movement can induce coal way of stacking is planned and monitored. Machines dust to explode. If enough coal is located in the vicinity of compress the material so to avoid creating voids and waste the explosion it can caught on fire. Stack effect occurs material is mixed to minimise coal concentration. when there are holes in the tip, usually vertical, chimney- Currently some spoil tips are undergoing monitoring like, that allowed for air to move from the outside thru process. However this is usually done in a traditional way. spoil tip with large speed. This also provides oxygen for Responsible personnel walks the area and looks for fire, the fire that started inside. Depending on the size of the land slide or holes in the structure. In winter this survey tip, amount and kind (age, fraction, placement etc.) of also includes looking for places with vast vegetation or flammable material and amount of oxygen being lack of snow cover. This may be unsafe for person transferred inside the speed in with the fire grows varies. responsible since spoil tips burn from the inside usually It can take up to few years before signs of fires become seem normal on the outside. Stepping on a fine cover may visible as flames or smoke. In a meantime tip’s stability cause the hole to appear or poisonous gas to emerge degradation, contamination of the water etc. can occur. [7,15,17]. Stability can be so demolished that fire brigades are unable In the view of recent spoil tips fires and landslides of to enter the structures safely while trying to extinguish the tips within open pit mines some government organizations

* Corresponding author: [email protected]

© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/). E3S Web of Conferences 26, 00008 (2018) https://doi.org/10.1051/e3sconf/20182600008 2017 BGC

3.1 3D discreet model – Digital Terrain Model – – could be implemented within mine’s environmental – 3D representation of a terrain’s surface defined 2 Spoil tip of LW Bogdanka coal mine area of spoil tip of Lubelski Węgiel „Bogdanka” S.A coal mine in December of 2015. LW “Bogdanka” hard Spoil tip of “Bogdanka” coal mine is supplied with two Fig. 1. Point cloud of “Bogdanka” spoil tip done with RIEGL – (200÷20 mm), 30– – – 3 3D and thermal survey of Bogdanka spoil tip

2 E3S Web of Conferences 26, 00008 (2018) https://doi.org/10.1051/e3sconf/20182600008 2017 BGC

3.1 3D discreet model – Digital Terrain Model – and faster in postprocessin and time of field surve would not increase sinificantl – – hermal Diital errain odel is a tpe of D with could be implemented within mine’s environmental added information on surface temperature n case of discreet D it simpl means that an etra column, – 3D representation of a terrain’s surface defined representin temperature is added here are multiple was of obtainin value of 2 Spoil tip of LW Bogdanka coal mine temperature of an obect n this case a remote method had to be used due to the sie of the obect, time manaement and minimisin crew presence on the tip emote was include infrared cameras that detect and reister the area of spoil tip of Lubelski Węgiel „Bogdanka” S.A radiation in the loninfrared rane of the electromanetic coal mine in December of 2015. LW “Bogdanka” hard spectrum hen tefanoltmann or lans laws that bound the heat emitted from the object with object’s temperature are bein used ameras used in thermoraph measure strenth of emission of electromanetic waves (that come from a certain direction) he value of temperature depends on the Spoil tip of “Bogdanka” coal mine is supplied with two strenth of received sinal his is called radiation flu ll obects emit a certain electromanetic strenth of loninfrared wave , t is possible to create a hermal D with the use of pictures an scans done from a plane, usin standard photorammetric method , 2, 3 owever the aim of this stud was to create a sstem that could be used in all conditions and did not reuire an outside help his is Fig. 1. Point cloud of “Bogdanka” spoil tip done with RIEGL wh a new 00 laser scanner euipped Fig. 2. op panorama from laser scanner with am with am ev 0 thermal camera was used his ev 0 etension ottom point cloud coloured to some camera is calibrated with laser scanner and provides the etend with temperature 0 same eometric results as internal camera t is possible to cover the point cloud with colours from thermal imaes hat is worth to mention that this method is relativel automaticall provided the usae of appropriate fast durin the surve what is etremel important in software his point cloud can be later eported in to other thermal imain hanes in liht, temperature of the formats and edited , 0 atmosphere and even amount of water vapour can mae – his laser scan was performed on two, potentiall most imaes incomparable (if not done in the same conditions (200÷20 mm), 30– – susceptible to fires and lads slides parts of the slopes he an over a short period of time) his is wh such surve – result was 2 laser scans reistered manual with the use of should tae as little time as possible and presented sstem natural elements ater on those scans were reistered allows for that aain and connected to the point cloud from laser scanner so to create a proper 3D thermal model of the structure esults of such an eperiment were satisfactor to some etent here was little problem with reisterin the lon rane scans, the connected not onl with the use of one of previousl presented surve methods ive the elements of the spoil tip but also nearb buildins and information on inside structure of the spoil tip n order to mines chimnes were used owever reisterin fill this data ap a seismic method was used to monitor the vicinit of the obect 3 3D and thermal survey of Bogdanka scans has proven to be difficult due to the lac of easil identifiable elements in the vicinit lso the rane of the ultichannel analsis of surface waves is one of the spoil tip am ev 0 camera was not satisfactor at all times most popular seismic method for obtainin information on the properties of the subsurface he method reuires a can stations in some cases had to be place in 0 to 20 controlled seismic source of ener, such as hammer etc metre distance from the ede of the spoil tip Distance that induces a surface wave properl placed set of from the scanner to the top was more than 0 metres which eophones, receives enerated seismic waves and was apparentl to fair for cameras software n most scans measures time that waves tae to travel from the source some thermal data was cut off thus livin top parts of the (each eophone detects them separatel) f the dispersion tip without thermal information (point cloud eisted) curve of surface wave is nown it is possible to set a (i 2) t is recommended to place scanner stations closer process of seismic inversion to build up subsurface model to an obect in order to et more reliable thermal 2, 3, information lso, in case of such obect, scanner travers he acuisition was completed with the use of with stabilised scan stations of nown coordinates would seismic sstem with the use of 2 and 0 prove to be more effective he would be more accurate eophones placed alternatel Distance between

3 E3S Web of Conferences 26, 00008 (2018) https://doi.org/10.1051/e3sconf/20182600008 2017 BGC

eohones was at m what reates to interna that diita forma but aso ans and drawins shoud corresond with metre seismic deoment t each of be ien them a series of sinas in metre interas was inducted he reaisation of this roject too das of on side eohone sreads and resonse rofies were created wor incudin ainin access reiminar wa on the eismic monitorin was done in three reions two bein object and atherin eistin data from the mine he fied fat areas on the to of the object and one on the west ersonne aried but neer was more than three eoe soe n this area therma monitorin was erformed and n in two instance scan stations of scanner no fire source or other therma anomaies were detected and eohsics acuisition reuired resence of one or his area was treated as a base of idea maintained area two eoe on side of the ti ost rocessin too about t was used as reference area durin ost rocessin since das howeer it was art done simutaneous when there were no otentia fire oids detected eohsics acuisition was bein erformed scans were reistered and rocessed he roject ended with iin a detail rapport to LW “Bogdanka” environmental diision ersonne was satisfied with uait and uantit of the resuts his roject shows that it is ossibe to combine data obtained b mutie seciaists into one mode and that with roer annin resuts coud be enerate fast his bein imortant in the iew of ensurin ubic safet and enironmenta contro

he roject was funded b statutor funds of no and

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4 E3S Web of Conferences 26, 00008 (2018) https://doi.org/10.1051/e3sconf/20182600008 2017 BGC

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he roject was funded b statutor funds of no and

1. J. Amorós López, E. Izquierdo Verdiguier, L. Gómez Chova, J. Muńoz Marí, J.Z. Rodríguez Barreiro, G. Camps Valls, J. Calpe Maravilla,

ISPRS Journal of Photogrammetry and Remote Fig. 3. utichanne anasis of surface waes – obtained Sensing, 66 (1), 115 (2011) rofies 2. M. de Berg, M. van Kreveld, M. Overmars,