sign in sign up
<<
Home , Land reclamation

10.2478/sggw-2018-0016

Annals of Warsaw University of Life Sciences – SGGW Reclamation No 50 (2), 2018: 195–211 (Ann. Warsaw Univ. of Life Sci. – SGGW, Land Reclam. 50 (2), 2018)

Analysis of the causes and effects of in the Carpathian flysch in the area of Milówka and evaluation of their prevention methods

MAŁGORZATA JASTRZĘBSKA, MARIAN ŁUPIEŻOWIEC Faculty of Civil Engineering, Silesian University of Technology, Gliwice, Poland

Abstract: Analysis of the causes and effects of Geological Institute shows that 95% landslides in the Carpathian flysch in the area of the landslides in Poland occur in the of Milówka and evaluation of their prevention Carpathian area, some occupy from 30 methods. The paper presents a comprehensive stu- to 40% of the gmina’s area. The first at- dy on the causes and effects of landslides occur- ring in the gmina Milówka (gmina is the admini- tempt to list the landslides in Poland was strative district in Poland, similar to a commune or undertaken in the years 1968–1970. municipality) from 1947 until today. The analysis At that time, they were estimated at includes the identification of probable causes of 8,500, and 2,970 of which posed a threat landslides and a discussion of possible remedial to residential buildings. Since then, methods, including preventive ones. The following phenomena have intensified to were considered: results of laboratory, geophysical the alarming level (www.pgi.gov.pl). In and seismic tests; meteorological data; vegetative and transpirational of plants and agricul- 2010 a special landslides counteracting tural crops; intensity of farming; forest clearance. program was introduced called system Attention was also paid to the tree-ring eccentricity osłony przeciwosuwiskowej (abbrevia- among spruces. Additionally, a numerical analysis tion SOPO). The primary objective of of the current landslide stability was carried out in SOPO is an ongoing monitoring of the Z_Soil program. Finally, it was found that de- threatened areas (Fig. 1). The basis of termining the exact value of the stability coefficient activities is an underground observation is not possible due to the numerous assumptions necessary for the numerical analysis. However, it (, ) and over- is possible to predict with high probability which ground (GNSS satellite scan, laser scan- of the slopes are threatened with landslides. ning, interferometric synthetic aperture radar – InSAR, rain gauges). Key words: landslides, stability analysis of the The authors seek to determine the cor- slopes and escarpments, gmina Milówka relation between this phenomenon and atmospheric precipitation and anthropo- INTRODUCTION genic factors, such as the forest clearance or shrinkage of agricultural fields on the The landslide problem concerns moun- slopes. tainous areas (but not only) around the Transpiration properties of plants play world. Data collected by the Polish a significant part in maintaining water 196 M. Jastrzębska, M. Łupieżowiec

FIGURE 1. A map of landslides with SOPO monitoring (www.pgi.gov.pl) balance in the substrate. For example, computational model, assessment of the the alfalfa needs 859 l and a larch needs accuracy of geological and geotechnical 1,165 l of water in order to produce 1 kg research on rock mass and appropriate of dry mass. This is the reason why in interpretation of the obtained param- the case of large areas threatened by eters, determination of the impact of landslides, solutions developed by bio- on and water conditions, technical engineering (including the determination of filtration coefficients, construction of terraces, regulation of and analysis of possible solutions, e.g. soil–water relations, afforestation, etc.) by draining water out of the colluvium are introduced (Begemann and Schiechtl of landslide. 1999). In the 1980s a new direction in deter- Each proposed solution (engineering mining the landslide phenomena called or biotechnical) is preceded by a thor- dendrogeomorphology appeared (Shro- ough analysis of a specific case, which der 1980, Butler 1987). It is based on the is extremely complex in relation to the conviction that the external disturbances Carpathian flysch. correspond to changes in the anatomy of Flysch is a heterogeneous, discon- wood e.g. the deconcentricity of the tree- tinuous and anisotropic medium. The -growth radial. This idea was developed landslide phenomena occurring in it by, among others, Wistuba and Malik most often arise as a result of shifting of (2011), followed by Wistuba et al. (2012, weak weathered top layer following the 2013, 2014) by introducing the substrate underlying strong layer (usually rock), sliding activity index (deconcentricity caused by a change in water relations index method). When comparing decon- and a decrease in the strength parameters centricity of the tree-growth data with of the weak layer (Instruction 2009). For rainfall data, it is possible to reconstruct this reason, each analysis concerns many previous mass movements of the ground threads and contains elements such as: and determine the threshold conditions reconstruction of the adverse phenom- triggering such phenomena (dendro- ena history in a given area, creation of chronology). The effectiveness of the Analysis of the causes and effects of landslides in the Carpathian flysch... 197 method was confirmed in the studies Municipal Office of Milówka (Cempura conducted on the Keprnícký landslide et al. 2009, Documentation 2010a, b, (Hrubý Jeseník, Eastern Sudetes, the 2011a, b, 2016). Czech Republic; Wistuba et al. 2012) A described landslide is located in and on the Milówka landslide (foots Milówka in the lower and middle part of of Prusów Mt 1,020 m a.s.l., southern the southern slope of the Prusów Moun- Poland, flysch Western Carpathians; tain. At the foot of the slope is located Wistuba et al. 2013, 2014). The above the stream called Salomonka flows. The mentioned studies have shown that area of landslides was mostly dominated dendrochronological analysis of growth by meadows with single trees, orchards, disturbances in trees is a promising arable lands, and only the lower part of approach to determine landslide hazards the slope was covered by mixed forest. in the extensive ranges. It can The access to the hamlets above the serve in early warning of the risk related stream Salomonka was located on the side to catastrophic landsliding. of the stream where the landslide forehead In the context of the presented infor- is now situated. The landslide is an old mation, a comprehensive analysis of the landslide, and although it was considered causes and effects of landslides occur- to be inactive. Studies of deconcentricity ring in the gmina Milówka from 1947 of tree-rings conducted by the team of until today has been conducted. Wistuba et al. (2014) in fact showed its alternating activity in 1947, 1950, 1962, MATERIAL AND METHODS 1968, 1977, 1993, 1997, 2004, 2007 and 2008. On 3 September 2010 there was Inventory of landslides and substrate another full activation, which resulted in exploratory study catastrophic consequences (Fig. 2). The Inventory of the existing state was con- cause of the landslide was the ducted on the basis of the site inspection of rainwater into the soil mass. The land- of landslide in Nieledwia, in Siedloki slide covered the area of almost 12 ha, and and on Prusów mountain and on the basis the average ground movement speed was of materials received from the Polish 2 cm/h. It is worth noting that on 5 Sep- Geological Institute (PIG) and from the tember 2015, the whole landslide area was a b

FIGURE 2. General view of the damage on the Milówka Siedloki landslide in September 2010 (www. onet.pl): a – a part of a landslide; b – destroyed regional road 198 M. Jastrzębska, M. Łupieżowiec still subject to massive movements on its amounted to over 6 m (Fig. 3). Within entire surface, resulting in the destruction the colluvium of the landslide there were of the county road and tightening the Salo- numerous secondary niches, crevices and monka riverbed (Fig. 2). In the upper part cracks (Fig. 4) filled with water during of the landslide, surface displacements rainy periods. The strong hydration of the a b

FIGURE 3. General view of horizontal displacements on the Milówka Siedloki landslide in June 2015 (Dziedzic and Golan 2016): a – upper edge of a landslide; b – main landslide threshold a b

FIGURE 4. General view of the colluvium of the landslide in Milówka Siedloki (Dziedzic and Golan 2016): a – “a drunk forest”, niche filled with water; b – visible cracks – winter 2014/2015 Analysis of the causes and effects of landslides in the Carpathian flysch... 199 colluvium is also confirmed by presence strength characteristic based on CD+u of the typical plants for . Finally, tests (φ' = 27.8°; c' = 5.3 kPa; φ' = 25.6°, the following were destroyed: four resi- c' = 7.9 kPa). Samples for testing were dential buildings, four outbuildings, one taken from six different depth levels up summer house, one building under con- to 9.0 m, on which the movement of soil struction, low and medium voltage line, masses was observed. The ground water telephone line, access and regional was drilled at a depth of 2.75 m. The road (including 2 bridges). Area protec- was deepened to 30 m and used tion – related works after the disaster cost for observations. During the PLN 3.2 mln (Gardas 2011). observations three potential slip surfaces At the same time, a research program were found, respectively at the depths of: was initiated. A set of geotechnical tests 12.9, 20.9 and 21.8 m. was carried out at the request of the PIG Laboratory tests were supplemented at the Institute of Geotechnics of the with geophysical tests carried out by Cracow University of Technology (Doc- Przedsiębiorstwo Badań Geoficznych umentation 2011b). The tests included Sp. z o.o from Warsaw (Documentation the basic recognition of the physical 2011a). The location of the profiles is characteristics of six samples with an shown on the map (Fig. 5). The seismic intact structure (natural profile is marked with a blue colour, and w = 14.42–36.32%; CaCO3 content: the geoelectric profile is marked with an 1% and 1–3%; γ = 19.6– orange colour (the ERT, electro-resist- –23.3 kN/m3; grain size distribution) and ance method).

red line – landslide border; orange line – geoelectric profile; blue line – seismic profile

FIGURE 5. Map of the geophysical works on the landslide in Milówka Siedloki (Documentation 2011a) 200 M. Jastrzębska, M. Łupieżowiec

FIGURE 6. The argillaceous schist outcrop in the bottom of the stream (Dziedzic and Golan 2016)

On the basis of seismic profiling along very rarely. The most common method the slope (Documentation 2011a), three is the of the as a way to layers with different parameters were protect the land against the formation of separated. The highest layer with the landslide or its activation. Correct water smallest thickness has been classified as drainage is very important for ensuring and debris with a maximum thick- stability, because the immediate cause of ness of about 5 m. The middle layer was most landslides are heavy rains. There- classified as a strongly cracked and - fore, maintenance of existing running aged rock mass, with a thickness ranging waters should be carried out so that rain- from 8 m to about 30 m. The depth of water from the upper parts of the slope this layer represents the potential slip can be effectively drained. In addition, surface. The third, lowest and intact cultivation of appropriate plant species layer is a solid rock substrate made of is also important. It is not surprising that sandstone interlaced with argillaceous landslide activation is often associated schist, which is very visible in the with negligence in this area. , as shown in Figure 6. Limitations concerning the use of All slip surfaces are located in layers the slope, which mainly consist in the of black marly shales that are interlaced reduction of sliding loads are preventive with cracked sandstone. It is a very unfa- methods as well. It is not surprising that vorable arrangement due to the acceler- in areas threatened by landslides, spatial ated infiltration of water into the shales development plans definitely limit devel- (towards the surface of the slip), which opment of constructions and in the case of significantly reduces their strength. such planning permission, it is necessary to carry out a series of additional analy- Landslide prevention methods ses. Obviously this way safety margin Prevention methods used for building increases, however, it does not constitute slopes are extremely expensive due to an additional reinforcement for the soil very large soil masses, which must be or rock substrates or a support for the well secured. Therefore, they are used ground masses. Retaining structures, that Analysis of the causes and effects of landslides in the Carpathian flysch... 201 can be considered supporting methods, measurement results may indicate the are made in places particularly exposed risk of landslides activation. to the risk of large material losses, such as roads or buildings. Retaining struc- Methods of tures are solid concrete or stone retain- The escarpment and slope stability ing walls (investments made in the past), analysis is carried out to assess the safety as well as cantilever retaining walls, margin with regard to the risk of land- counterfort retaining walls or anchored slides, sluffs and other similar destruc- retaining walls. However, it should be tive effects on the slope surface. As was noted that this type of support is made previously mentioned, these phenomena only on very short fragments and does may be a threat to life or health of people not constitute a protection for the entire staying nearby, as well as serious mate- slope. They are implemented in places rial losses. Stability analysis methods can particularly exposed to the occurrence be divided into three groups. The first of ground mass movements or where method focuses on finding a shape of a the consequences of landslides are par- slope that is located near the limit state. ticularly severe. This applies to mainly This condition is most often described as roads or existing buildings, especially the Coulomb-Mohr model, and the pa- those inhabited. Finally, the last of the rameters determining the stability are co- discussed methods of securing the slopes hesion and angle of internal . The is . This method consists in most popular method is the Sokołowski’s introducing ground nails of specified method. In order to use it in practice, length into the (it depends on the various types of nomograms have been location of the hypothetical slip surface), created (Wiłun 2013). An important draw- which sometimes reaches even 20–30 m. back of this group of methods is the lack This solution is very expensive and is of possibility to include soil stratification only used in areas requiring special pro- (using the weighted mean of parameters tection. What is more, nails are not usu- value does not solve the problem) and ally used to protect the entire slopes that the influence of water flow pressure. cover extensive areas. Therefore, nowadays this method is The safety of slopes is enhanced by very rarely used and its only application monitoring, which may be perfectly is the preliminary assessment of slope described as the observational method stability. The second group of methods of geotechnical design, which is pro- that are nowadays quite often used are vided by the EN-1997-1:2004 standard. strip (block) methods. These types of It is necessary to provide displacement methods are based on the analysis of the control at specially installed measur- equilibrium of thought-separated blocks ing points. Inclinometer observations of soil along the slip surface defined by are crucial because they enable very the user (Madej 1981). Depending on fast detection of an activated landslide the assumptions regarding cooperation and the location of slip surfaces. Proper between blocks, the following methods monitoring allows to take the immediate can be distinguished: Fellenius, Bishop, security measures in a situation when the Janbu, Morgernstern–Price and many 202 M. Jastrzębska, M. Łupieżowiec others. The stability factor (F) is de- elements where the plasticity surface has fined as the ratio of generalized forces been reached. Further reduction of the maintaining the system (Mult), usually parameter values requires redistribution moments relative to a specific point, to of stresses, which is carried out during the interactions causing the sluff of the the iterative procedure. The procedure is soil (Mall), which can be presented by the carried out until the lack of convergence formula: of iterations is reached, which leads to the mechanism of destruction. The cor- M F = ult responding stability coefficient value is M all calculated from the formula:

The main causes of landslides are: c tg ij F=00 = unit weight of solid, water flow pressure c fftg ij and additional loads resulting from, for example, exploitation, while retention where: forces result from the c0, φ0 – values of strength parameters of the soil along the slip surface. The – a perfectly plastic Coulomb– strength is usually described by Cou- –Mohr model of accumu- lomb’s dependence, and the parameters lated in the slope substrate, esti- are c and φ. These methods are very mated on the basis of geotechni- often used for practical issues. Their cal diagnosis; weakness is the necessity of providing cf, φf – parameter values at the point of the surface with the initial slip, which destruction mechanism of the should rather be the result of calcula- slope. tions. This type of methods allows to inlcude the inhomogeneity of the ground The value of the factor F greater than and the influence of water, which is not 1.00 indicates that the slope is stable, possible in the case of methods based on although the safety margin is not always the analysis of the state of stress. Block sufficient. A value of exactly 1.00 means methods usually do not apply to analyses that the slope is in the limit state. Values of three-dimensional issues, although the lower than 1.00 cannot be obtained by the latter are extremely rare. above calculation, as it is not possible to A concept that is free from the above generate a state of stress in the substrate drawbacks is the use of the finite element at the slope instability. The reduction method in estimating the stability coeffi- procedure of c–φ can be used if the Cou- cient value. After the stress state has been lomb–Mohr or Drucker–Prager model generated in the ground mass of the slope, were used for the analysis, parameters the procedure of c–φ strength reduction are the above mentioned and is used. The procedure consists in grad- angle of internal friction. In the case of ual lowering of the values of strength other elastic-plastic models, the stabil- parameters (cohesion and tangent of the ity estimation procedure can be adjusted internal friction angle), which results in gradually by reducing the values of the the formation of plasticity zones in the parameters determining the location of Analysis of the causes and effects of landslides in the Carpathian flysch... 203 the plastic surface at a given point (stress efforts are required to strengthen the level method). An undoubted advantage slopes. of the presented method is the fact that the surface of the slip is the result of RESULTS AND DISCUSSION analysis, and it is not preassumed by an user. In addition, it is possible to include Analysis of landslides in Milówka many factors in FEM, which are not The area affected by the landslide in included in other methods of analysis. Milówka consists of three significant These include the layering of the soil sub- areas: Milówka Nieledwia (on the left strate, the effect of the groundwater flow side of the Soła River, Nieledwia) and pressure, the various types of reinforce- adjacent Milówka Prusów and Milówka ments, any slope loading (also dynamic) Siedloki (on the right side of the Soła and many others. The disadvantage of river, the mountain called Prusów and the described method is that the result the hamlet called Siedloki at its foot). depends on the effectiveness of the itera- Landslide in the village of Nieledwia tive algorithm used during redistribution was activated in 2009. It posed a threat of stresses. However, differences in this on several sections of the S 1437 Milów- regard are on the safe side. ka-Nieledwia regional road which began At this point, it is worth analysing to slide down towards the stream called the requirements for the stability factor, Nieledwianka. After that situation, the which guarantee the safety margin. Of slope was stabilized and the road was course, the margin will depend on the renovated. Some of the works were car- type of construction (permanent or tem- ried out in 2009, and they were complet- porary) and the consequences of stability ed in autumn 2010. Another landslide loss. In the case of small level differences activated in the hamlet of Siedloki and between the and the base of the on the mountain Prusów in September slope or escarpment and temporary struc- 2010, during the work on the landslide tures, a sufficient value of the stability in Nieledwia. It was a result of heavy and factor is 1.10. The value required for the prolonged rainfall. Despite the fact that analysed slope is 1.30, which means that it covered a small area of that was 480 m there is a low probability of a landslide long and 300 m wide, its effects were and it guarantees the required safety disastrous (see chapter “Materials and margin (Kłosiński and Leśniowski 2009). methods”). As a result, it was necessary In the case of investments, to: rebuild the road section of 0.5 km and even more stringent requirements are electric and telephone networks, clear applied. A value of 1.50 is demanded in the stream of Salomonka and secure the the case of excavation slopes and motor- mountain slope of Prusów. way embankments and modernization of railway lines, and even 2.0 for new rail- Landslide of Milówka Nieledwia way investments (Instruction Id-3). It is The design office “Zamek” from Kraków not difficult to notice that such require- designed three retaining walls in the ments are not imposed due to safety rea- lower, middle and upper part of the sons and further that significant financial village in order to stabilize the regional 204 M. Jastrzębska, M. Łupieżowiec road S 1437. These were retaining ribbed dilatation appeared, contrary to the other walls with different heights and lengths walls with significant displacements. In of dilated segments. The main wall and addition, no longitudinal cracks in the ribs were 0.3 m thick. The Gonar rod asphalt were observed, which indicates system with metal heads concreted into the stabilization of the displacement and a bench of and a drainage the inhibition of the landslide. system for areas located above the road was suggested as an additional security. The landslides in Milówka Prusów In the constructed reinforced concrete and Milówka Siedloki box, it was possible to re-grow vegeta- The risk of mass movements is still real tion due to filling it with native soil (the on this location, which is confirmed by item was included in the analysis of the the numerical stability analyses. Securing stability of the system). Therefore, it was the landslide against further escalation in a combination of an engineering and a large area is practically impossible due biotechnical solutions that blended in to the potential costs. After the analysis with the surroundings very well (Fig. 7). of the causes, it was found that future Linear drainage was done behind the stabilization works should maximally central retaining wall on the road side drain this area and reduce the amount of parallel to the axis of the wall, i.e. water infiltrating the colluvium. Finally, parallel to the upper edge of the formed the surrounding drainage was suggested landslide, and the rainwater was drained fo the landslide crown (about 1,500 m), to the absorption (Fig. 7b). which cuts off the inflow of water from Observations from July 2015 con- the top of the slope to the colluvium and firmed the effectiveness of the applied discharges the rainwater to the nearby solutions, especially in the case of the Salomonka stream (Fig. 8). Additionally, central retaining wall, in which the mini- it was recommended that the colluvium mum dilatation and displacement of the areas should be filled with plants that a b

FIGURE 7. Retaining wall on the landslide Milówka Nieledwia (Dziedzic and Golan 2016): a – upper retaining wall; b – middle retaining wall with an absorption well Analysis of the causes and effects of landslides in the Carpathian flysch... 205

FIGURE 8. Proposed scheme for linear landslide drainage in Milówka Siedloki (Dziedzic and Golan 2016) have good transpiration properties (e.g. calculations, which may be part of the alfalfa, rye, oats, larch, beech). It would monitoring of landslide danger. Some be possible to resign from the latter, simplifications are always used when provided that regular grass trimming creating the model. They arise from will be planned and conducted, which the limitations concerning the available was neglected after 1989. There are methods and programs, which are tools many indications that the abandonment for solving a given issue. Lack of proper of agricultural fields, that absorb huge ground tests is also often a limitation, amounts of water from the soil, is one of especially in terms of the parameters of the important factors affecting landslide the model adopted for the calculation. activity (especially in Milówka). The most popular material model for stability analysis of slopes is the Numerical analysis of the stability elastic-perfectly plastic model with of the landslide in Milówka Prusów a Coulomb–Mohr failure criterion. The and Siedloki required values of parameters are the The article presents the stability analysis Young’s modulus (E) and the Poisson’s of the Milówka-Prusów slope, where ratio (ν), which describe the behaviour in 2010 a landslide started. Correctness of the soil in the elastic range and the of stability analyses can be assessed effective angle of internal friction (φ') by knowing the soil conditions and the and effective cohesion (c'). Usually, existing deformations (Documentation a plane model is analysed using the 2016). After verifying the correctness of assumptions of a plane strain. Finite ele- the assumptions, the conclusions from ments used are a four-node quadrangle. the analyses may be used for future There were three variables in each node: 206 M. Jastrzębska, M. Łupieżowiec two displacements (horizontal and verti- urements (Documentation 2010a, b). cal) and the value of pore pressures. The Most often, the model’s floor is horizon- size of the model should be definitely tal, which facilitates the task of boundary larger than the expected range of the conditions. However, it is also allowed landslide. Also, the depth of the model take a bottom that is parallel to the slope, should be large enough not to affect the which reduces the number of finite ele- shape of the slip surface. The most fre- ments and causes a more favorable shape quent problem is too shallow exploration of these elements, which results in short- of the substrate in relation to the depth of ening the calculation time and improv- the built model. In such case, it is usu- ing convergence. In the present case, the ally assumed that the lowest discovered second method of the model geometry layer lies at the bottom of the constructed selecting was used. In numerical analy- model. ses, the finite element method was used, The numerical model used in the calcu- and the stability was analysed using lations is shown in Figure 9a. The model the previously described c–φ reduction limits the shape of the slope, which was procedure. The soil should be analysed mapped on the basis of geodetic meas- as a two-component medium consist- a

b

FIGURE 9. Numerical model in stability analysis: a – on the basis of soil exploration; b – on the basis of calibration including degradation of material (Dziedzic and Golan 2016) Analysis of the causes and effects of landslides in the Carpathian flysch... 207 ing of a deformable solids and filtering additional, forced stream of flow through water, because water in the ground plays the surface of the analysed slope (rain- a key part in the initiation and course of fall of 20 cm/day was assumed for two landslide processes. The filtration veloc- 10-day periods with 10-day break). ity is described by Darcy’s law, and the In the preliminary stage of the analysis, relationship between the total stress, the the stress state was determined, including and the pore pressure in the filtering phenomena in the substrate. the soil is determined by Terzaghi’s law. At a later stage, the change in the stress The values of material parameters for state associated with rainwater infiltration calculations are summarized in the was analysed. Both before and after the (Dziedzic and Golan 2016). The bound- rain a stability analysis was carried out ary conditions in the deformation analy- using the c–φ reduction method. In addi- sis of the solid were set in the form of tion, a variant with the forming of two non-displaceable supports on the bottom layers simulating slip on the border of edge of the model and supports without sandstones and weathering was analysed the possibility of horizontal displace- (Fig. 9b). In this variant, the following ment at the side edges. The boundary factors were considered: degradation of conditions on the surface of the slope strength due to landslide initiation and were automatically set as surface normal increase of the filtration coefficient (the stress equal to zero. The boundary condi- table). In order to be able to apply this tions of water filtration were set in the variant of calculations, it is necessary to form of piezometric heights of water know the course of the forming slip sur- levels at the lateral edges, the height was face and to be able to estimate the values provided based on the . On the of the degraded layers parameters. This bottom and top edges of the model, zero information can be obtained from the water flow rates were applied. Addition- analysis of monitoring results. The value ally, rain was included into analysis as an of stability coefficient lower than 1.00

TABLE. Values of strength parameters for numerical analyses (Documentation 2011b, Dziedzic and Golan 2016) Effective Bulk Young’s Poisson’s internal Effective Darcy’s Material zone density modulus ratio friction cohesion factor γ (kN/m3) E (MPa) ν (-) angle c′ (kPa) k (m/s) φ′ (°) Surface layer (sandy silty 21.0 17.5 0.32 26 6 5·10–8 clay with sandstone crumbs) Top layer (shale) 23.1 400 0.33 20 10 5·10–7 Layer of sandstones 25.0 3 200 0.30 25 250 5·10–9 Layer of degraded 23.1 400 0.33 15 7.5 5·10–7 sandstones (only variant II) Layer of degenerate shales 25.0 3 200 0.30 25 7,5 5·10–7 (only variant II) 208 M. Jastrzębska, M. Łupieżowiec was obtained by proportional increase of under typical atmospheric conditions strength of all layers of the model with the (Fig. 10a). The value is so high that it can same reduction of the obtained result. be assumed that the slope is safe. In the The stability coefficient value is 1.21, case of heavy rains, this value decreases with the parameter values based on to 1.07 (Fig. 10b), which should be treat- subsoil exploration and water filtration ed as a serious risk of initiating landslide a

b

c

FIGURE 10. Slip surface shape: a – under typical atmospheric conditions; b – under heavy rains; c – model after calibration (Dziedzic and Golan 2016) Analysis of the causes and effects of landslides in the Carpathian flysch... 209 processes. Thus, the influence of rain- Another aspect of the protection water should be treated as the main risk of the slopes against the landslide is factor for the emergence of mass move- proper monitoring system, which should ments. include both soil exploration and regu- The origin, range and form of soil lar displacement measurements. The mass movements can be accurately conclusions from the deconcentricity of presented in the case of when detailed trees annual growth can be additionally information about potential slip surfaces used. The monitoring is supplemented by and the values of the parameters of the numerical analyses, including the most degraded layers forming the slip layer important slope stability analyses, on the are provided. The value of the stability basis of which the current safety margin coefficient for variant II is 0.89, and the can be assessed. The method of stabil- form of loss stability quite well corre- ity analysis based on the FEM proposed sponds to the real slides (Fig. 10c). The in the paper makes it possible to obtain shape of all slip surfaces is flattened and a reliable mechanism of destruction. approximately parallel to the slope sur- Having such tools at their disposal, the face. This is the result of the formation responsible entities can definitely make and stratification in the substrate, as well easier the important decisions regarding as the formation of preferential filtration the safety of people using the endangered directions and the simultaneous effect areas and structures located there. of the hydrostatic pressure. Thus, the proposed method of analysis can be very REFERENCES effective provided that proper values of the model parameters and the stratifica- BEGEMANN W., SCHIECHTL H.M. 1999: In- tion are used. żynieria ekologiczna w budownictwie wodnym i ziemnym [Ecological engineering in hydrous and ground construction]. Arkady, Warszawa CONCLUSIONS [in Polish]. BUTLER D.R. 1987: Teaching general principles With regard to the presented analyses, and applications of dendrogeomorphology. it can be concluded that water is the J. Geol. Ed. 35 (2): 64–70. CEMPURA Ł., KOS J., SOKALSKI J. 2009: main factor initiating the landslide proc- Mapa osuwisk i terenów zagrożonych ru- esses. This is due to both observations chami masowymi ziemi dla gminy Milówka and numerical analyses. Thus, the key [Map of landslides and areas threatened by task for the land manager is to properly mass land movements for the Milówka com- drain the water when it suddenly occurs, mune]. Przedsiębiorstwo Geologiczne, Kra- ków [in Polish]. which happens mainly with heavy rains. Documentation 2010a: Operat pomiarowy. Moni- Proper removal of water is the efficient toring geodezyjny osuwisko „Prusów” w Mi- drainage or cultivation of appropriate lówce. Obserwacja przemieszczeń osuwiska plant species that guarantee bioretention. w dniach: 13.09.2010–11.10.2010 [Measuring In addition, the plant root system may elaboration. Geodetic monitoring of the landsli- de „Prusów” in Milówka. Observation of lands- provide additional reinforcement of the lide dislocations on: 13.09.2010–11.10.20101]. slope, which increases the safety of its Usługi Geodezyjne „Geo-Profil” s.c., Żywiec use. [in Polish]. 210 M. Jastrzębska, M. Łupieżowiec

Documentation 2010b: Operat pomiarowy. Mo- Instruction 2009: Ocena stateczności skarp i zbo- nitoring geodezyjny osuwisko „Prusów” czy. Zasada wyboru zabezpieczeń [Stability w Milówce”. Obserwacja przemieszczeń assessment of slopes and escarpments. The osuwiska w dniach: 11.10.2010–27.12.2010 principle of the protection selection]. Instruk- [Measuring elaboration. Geodetic monito- cja ITB, Warszawa [in Polish]. ring of the landslide „Prusów” in Milówka. Instruction Id-3 2009: Warunki techniczne utrzy- Observation of landslide dislocations on: mania podtorza kolejowego [Technical con- 11.10.2010–27.12.2010]. Usługi Geodezyjne ditions for maintaining the railway subgrade]. „Geo-Profil” s.c., Żywiec [in Polish]. PKP PLK S.A., Warszawa [in Polish]. Documentation 2011a: Badania geofizyczne osu- MADEJ J. 1981: Metody sprawdzania stateczno- wisk karpackich w ramach tematu: „System ści zboczy [Methods of verification of the slo- Osłony Przeciwosuwiskowej SOPO – etap II pe stability]. WKŁ, Warszawa [in Polish]. – 2011 rok” [Geophysical tests of the Carpat- KŁOSIŃSKI B., LEŚNIOWSKI Ł. 2009: O wy- hian landslides under the theme: „SOPO anti- maganiach dotyczących stateczności zboczy landslides system – stage II – 2011”]. Przed- i skarp [The requirements for the stability of siębiorstwo Badań Geofizycznych Sp. z o.o., slopes and escarpments]. Zesz. Nauk. Techn. Warszawa [in Polish]. SITK, Kraków. Mat. konf. Problematyka osu- Documentation 2011b: Wykonanie badań la- wisk w budownictwie komunikacyjnym 88 boratoryjnych próbek pobranych z wierceń (144) [in Polish]. pełnordzeniowych, wykonanych na 15 mo- SHRODER J.F. 1980: Dendrogeomorphology: nitorowanych obiektach osuwiskowych wraz review and new techniques of tree-ring dating. z interpretacją i dokumentacją końcową za- Prog. Phys. Geogr. 4 (2): 161–188. wierającą opracowanie warunków geotech- WIŁUN Z. 2013: Zarys geotechniki [Geotechni- nicznych dla potrzeb monitoringu wgłębnego cal outline]. 10 edn. WKŁ, Warszawa [in Po- osuwisk. Osuwisko „Milówka” [Realisation of lish]. laboratory tests of samples taken from full-core WISTUBA M., MALIK I. 2011: Indeks dekon- drilling, carried out on 15 monitored landsli- centryczności przyrostów rocznych drzew des, including interpretation and final docu- — narzędzie do identyfikacji współczesnych mentation with the elaboration of geotechnical ruchów osuwiskowych [Index of the annual conditions for the needs of deep landslide mo- tree-ring eccentricity – a tool for identifying the nitoring. Landslide „Milowka”]. Politechnika modern landslide movements]. Czas. Geogr. 82 Krakowska, Kraków [in Polish]. (4): 401–421 [in Polish]. Documentation 2016: Karta dokumentacyjna WISTUBA M., MALIK I., GÄRTNER H., KOJS osuwiska. Numer ewidencyjny 24-17-092 P., KRĄPIEC M. 2012: Zastosowanie dekon- [Landslide documentation card. The registra- centryczności przyrostów rocznych świerka tion numer 24-17-092]. Państwowy Instytut pospolitego (Picea abies Karst.) w analizie dy- Geologiczny – Państwowy Instytut Badawczy, namiki osuwiska – przykład z masywu Hrubé- Oddział Karpacki, Kraków [in Polish]. go Jeseníka (Sudety Wschodnie) [Application DZIEDZIC G., GOLAN A. 2016: Analiza zjawisk of tree-ring eccentricity above spruce osuwiskowych we fliszu karpackim na przykła- (Picea abies Karst.) in the analysis of landslide dzie osuwiska w Milówce Prusów [Analysis of dynamics – example from the Hrubé Jeseník landslide phenomena in the Carpathian flysch massif (Eastern Sudetes)]. Stud. Mat. CEPL on the example of a landslide in Milówka Pru- Rogów 14 (30): 185–194 [in Polish]. sów]. Master’s thesis, The Silesian University WISTUBA M., MALIK I., PIĄTEK M., KOJS P., of Technology [in Polish]. KALINOWSKI M., POLOWY M. 2013: The EN-1997-1:2004. Eurokod-7. Geotechnical De- use of wood anatomy features for landslide- sign. Part 1: General rules. risk assessment and early warning – an exam- GARDAS Ł. 2011: Osuwisko w Milówce–Pruso- ple from Western Carpathians, Poland. Geoph. wie czeka na inwestycje. Dziennik Zachodni Res. Abstr. 15 (EGU2013-9899). EGU General z 14.04.2011. Assembly. Analysis of the causes and effects of landslides in the Carpathian flysch... 211

WISTUBA M., MALIK I., POLOWY M., Ostatecznie stwierdzono, że biorąc pod uwagę MICHAŁOWICZ P. 2014: Zastosowanie liczbę założeń koniecznych do przyjęcia w ra- dekoncentryczności przyrostów rocznych mach analizy numerycznej, określenie dokład- w badaniach stoku o wysokim zagrożeniu nej wartości współczynnika stateczności nie jest osuwiskowym (Milówka, Beskid Żywiecki) możliwe. Można natomiast wytypować z dużym [Application of tree-ring eccentricity in studies prawdopodobieństwem zbocza zagrożone osu- of a slope with high landslide hazard (Milów- nięciem. W tym celu autorzy sugerują skorelo- ka village, Beskid Żywiecki Mts)]. Stud. Mat. wanie danych odnośnie aktywności osuwisko- CEPL Rogów 16 (40): 130–138 [in Polish]. wej, pochodzących z Narodowego Archiwum Geologicznego, z danymi z meteorologicznymi Streszczenie: Analiza przyczyn i skutków osu- i danymi z urzędów statystycznych, które doty- wisk we fliszu karpackim na terenie gminy Mi- czą zasięgu i intensywności gospodarki rolnej na lówka oraz ocena metod ich zapobiegania. Praca terenach osuwiskowych (lub wycinki drzew, je- stanowi obszerne stadium dotyczące przyczyn żeli takie dane istnieją). Ponadto stwierdzono, że i skutków osuwisk występujących z różnymi zmienność masywów fliszowych uniemożliwia okresami intensywności na terenie gminy Mi- wypracowanie rozwiązań uniwersalnych. Często lówka od 1947 roku aż do dziś. Inwentaryzację dobrym zabezpieczeniem jest stosowanie trady- stanu istniejącego wykonano na podstawie wizji cyjnych metod stabilizacji w połączeniu z meto- lokalnej osuwisk w Nieledwi, Przysiółku Siedloki dami naturalnymi takimi jak planowanie wyko- i na górze Prusów oraz na podstawie materiałów szeń trawy na obszarze osuwiska i/lub obsadzenie otrzymanych z Państwowego Instytutu Geolo- powierzchni osuwiska drzewami lub roślinami gicznego w Krakowie i Urzędu Gminy Milówka. wysokoenergetycznymi. Każdorazowo konieczne Pełna analiza objęła wytypowanie prawdopodob- jest indywidualne podejście do zagadnienia. nych przyczyn tworzących się osuwisk oraz dys- kusję nad możliwymi metodami zaradczymi, w Słowa kluczowe: osuwiska, analiza stateczności tym profilaktycznymi. Pod uwagę wzięto również zboczy i skarp, gmina Milówka właściwości wegetacyjne i transpiracyjne roślin oraz upraw rolnych. Zwrócono również uwagę na dekoncentryczność przyrostów rocznych drzew. MS received 29.01.2018 Dodatkowo przeprowadzono analizę numerycz- MS accepted 04.06.2018 ną stateczności osuwiska w stanie aktualnym w programie Z_Soil. Za podstawę do budowy mo- delu przyjęto przekroje wyznaczone metodami Authors’ address: sejsmicznymi i elektrooporowymi, które dość Małgorzata Jastrzębska, Marian Łupieżowiec wiernie oddają skomplikowaną budowę geolo- Katedra Geotechniki i Dróg giczną fliszu karpackiego. Parametry gruntowe Wydział Budownictwa uzyskano z badań laboratoryjnych oraz geofi- Politechnika Śląska zycznych. Rozważono możliwości uwzględnienia ul. Akademicka 5, 44-100 Gliwice w obliczeniach numerycznych opadów atmosfe- Poland rycznych w postaci infiltracji wody w głąb zbocza e-mail: [email protected] przez system szczelin i spękań. [email protected]