Stability Of Natural Slopes Research Articles

Impact of climate change on natural terrain stability and infrastructure integrity: Insights and case studies from Colombia

AbstractClimate change often leads to increased precipitations and thus affects natural terrain stability, leading to landslides and infrastructure damage. Infrastructure failure causes economic losses, societal disruption, and hampers emergency response and recovery efforts. For example, a significant challenge to the stability of natural slopes is the intensification of heavy precipitation events due to climate change. Increased precipitation rates can intensify soil erosion and soil saturation, resulting in increased instability and a higher risk of slope failure. This work consolidates current insights derived from practical engineering based on detailed investigation as well as rigorous research on the interplay between climate change, land‐use changes, geomorphological characteristics, and their collective influence on slope stability, landslides, and infrastructure integrity. Two case studies from South America are presented to analyze such effect of climate change. Collaboration between civil engineering and climate disciplines, foremost meteorology along with predictive risk management, is essential for sustainable infrastructure in evolving climates.

ANALISIS GEOTEKNIK DAN KESTABILAN LERENG TOWER SUTT PT. PLN (Studi kasus: TW. 203 Pembangunan T/L 150 KV GI KAMBANG – GI TAPAN)

Slope instability is caused by several lithological and structural factors, slope geometry, relative relief, ground water, as well as changes in use and land cover. Mountainous areas, development and expansion of infrastructure networks can inadvertently cause natural slope shifts, thereby negatively impacting the stability of the excavated slope. Analysis of the geotechnical properties of soil and rock is important for understanding and predicting the possibility of landslides at certain locations. Geotechnical analysis is needed to carry out slope stability analysis which is carried out using GEO5 software. Construction of T/L 150 KV GI Kambang – GI Tapan, Tower TW. 203 with a tower structure at the top of the slope. Based on these conditions, a comprehensive study is needed to analyze the stability of natural slopes due to tower loads. Soil Type, Parameters c' and ?' (Drained), Parameters Cu and ? (Undrained) and soil properties index are based on CPT test results. The Bishop, Spencer, Janbu and Morgenstern-Price methods on natural slopes, tower loads, Natural with Tower+Pile Loads, Natural Slopes with Tower+Pile Loads, Earthquake Loads produce a safe condition against failure in Short-Term (Construction) and Long-Term conditions. Term (Operational). Analysis of the Fellenius method on natural slopes and tower loads in Short-Term (Construction) and Long-Term (Operational) conditions shows unsafe conditions. The safety factors resulting from the Bishop, Spencer, Janbu and Morgenstern-Price methods do not show significant differences in values.

Stability of Natural Slopes and Determination of the Pressure of Incoherent Soils on Fences

Stability of Natural Slopes and Determination of the Pressure of Incoherent Soils on Fences

Reconstruction of Natural Slope Stability by Limit Equilibrium Methods and Finite Element Methods

Slope stability analysis is particularly important for natural slopes that are relatively undesigned to be technically safe. Natural slopes are prone to collapse depending on the condition of the slope material and rainfall. A comprehensive stability analysis using numerical methods to calculate the factor of safety and probability of collapse can be used as a reference to assess the safety of a slope. This study discusses boundary equilibrium and finite element in the analysis of slope safety factor and landslide probability by reconstructing the slope with landslide history. The reconstruction of the slope is based on the actual slope condition with saturated material due to rain that has a safety factor of 0.5 using mathematical methods which are then analyzed numerically in this study. The results of the factor of safety on the saturated condition slope have a value that is not much different from the actual condition with a 100% probability of landslide. The results of low shear strength values in each slice of the limit equilibrium analysis for saturated conditions also indicate that the slope is in an unsafe condition which is supported by the development of shear and tensile strains in the finite element method analysis in the slope slide plane area which causes the stress distribution in the actual landslide area to be unstable.

The effect of geological characteristics and earthquakes on natural slope stability analysis in landslide modeling using static and pseudostatic methods in Cianjur Area, West Bandung, Indonesia

The earthquake in Cianjur occurred on Monday, November 21, 2022. The epicenter was in Cugenang Subdistrict, Cianjur District, West Java Province. Cianjur is an area that is susceptible to landslides, which can be triggered by high rainfall and earthquake shocks. The Cianjur earthquake caused collateral hazard landslides that occurred in several locations. Based on the static and pseudo-static analysis, the pseudo-static analysis will provide information on how much the slope safety number decreases when earthquake loads are applied. This study aims (1) to calculate the safety factor value (SF) of slopes under static and pseudo-static conditions to assess the stability of the natural slope and (2) to determine the influence of geological characteristics and the Cianjur earthquake on slope stability analysis in landslides in Cianjur and its surroundings. Slope stability analysis was carried out using static and pseudo-static methods. This research result shows that the condition of the slopes of the study area before the earthquake occurred was in safe condition. The condition of the slopes in the study area experienced a decrease in the safety value of the slope from natural conditions to increased loads or earthquake shaking.

Stability Analysis of Residual Soil Slope Model by Numerical Modeling Using FEM Against LEM

Due to the advances of numerical simulation with computer modeling software, engineers and designers are gaining more interest in simulation methods for the prediction of soil behavior. Slope failure could be considered the most challenging aspect in geotechnical engineering. Accordingly, nowadays, many computer modeling software is employed for the evaluation of natural slope stability analyses. In this paper, the soil slope model analyses were implemented using the finite element analysis method (FEM) and simulated using PLAXIS-2D software. The parameters of soil layers used to feed these slope models were obtained from laboratory results by drained triaxial compression tests conducted on remoulded residual soil samples prepared under 200 kPa remolding pressure. This paper aims to present numerical simulations of natural slope stability by determining the failure surface and the corresponding safety factor with consideration to the influence of various slope geometries. Then, the obtained (FOS) values were then compared with previous results of similar slope models that were calculated by limit equilibrium analysis method (LEM) using SLOPE/W software. The evaluated results indicated that the change in the slope geometries could considerably influence the calculated FOS. Furthermore, the FE method calculated the safety factor close to but slightly higher than the results calculated by the LE method. Nevertheless, both methods are satisfying in obtaining the ideal mechanism of slope failure behavior. However, the application of (FEM) offers an attractive alternative to traditional approaches to the problem, especially for (LEM).

Effect of Strength Anisotropy on the Stability of Natural Slopes

It is well known that low plasticity soft clays have large variations in undrained shear strength with the direction of loading. Laboratory experiments show typically a cross anisotropic behavior, where the undrained shear strength in compression is significantly larger than the undrained shear strength in extension. The total stress based NGI-ADP model, as available in PLAXIS, captures such shear strength anisotropy well, when applied to embankments on or excavations from a horizontal or almost horizontal terrain. However, for non-horizontal terrain the direction of the in-situ principal stresses are inclined, and the axis of anisotropy are hence expected to be somewhat inclined too. As for natural slopes, the effect on the calculated factor of safety due to this inclination is not yet well documented. Previous studies show that this effect might not be a negligible effect and can increase the factor of safety by about 10% for gentle natural slopes. In order to study this, a new ADP model has been implemented in PLAXIS. The formulation is inspired by results from DSS laboratory testing where samples were consolidated under inclined effective stresses before shearing in the same or the opposite direction of the initial shear stress. As expected, the model shows higher factors of safety when applied to a slope than a conventional analysis. The paper then discusses to what extent this represents a real safety margin that has previously been neglected.

Deterministic and Probabilistic Approach in Slope Stability of a Tropical Soil

The stability of natural slopes in tropical regions is subject to erodibility due to the high periods of drought and rainfall. Thus, slope stability analysis is of great value for places subject to erosion. In addition, consideration of the dispersion of soil parameters used in stability calculations is important for a complete understanding of the failure probability of structures. Therefore, this paper analyzes the stability of a natural slope located in Luziânia, Goiás - Brazil and a study of the Probability of Failure by the probabilistic methods FOSM and PEM. In this study was showed distinct safety factors for the analysis in question.

The mechanical behaviour of rock specimens with specific edge crack distributions under triaxial loading conditions

Abstract Research on the mechanical behaviour of rock masses with multiple joints has become a popular topic and has practical applications in natural slope stability. This paper aims to clarify the influence of joint geometry, joint orientation and joint connectivity ratio on the mechanical behaviour of rock specimens containing two pre-existing joints. Triaxial compression tests were conducted under various confining pressures to simulate the variation in external conditions. An exponential criterion was used to describe the relationship between the axial stress and confining pressure. The experimental crack propagation was explored by varying the joint orientation, joint connectivity ratio and confining pressure. The structural plane with a greater angle of inclination controlled the failure of the rock sample. Two failure patterns were observed under the loading conditions: shear failure and mixed failure. The failure surface trajectory presented similar deviations with the increase in joint inclination angle, joint connectivity ratio and confining pressure, which also accelerates the transition from mixed failure to shear failure. The experimental results highlight the significance of elucidating the influence of structural planes in practical engineering to predict the stability of natural slopes.

Predictive modeling of static and seismic stability of small homogeneous earth dams using artificial neural network

The previous results of artificial neural network (ANN) prediction models in natural slope stability are encouraging, which gives logical hope for the practical application of these models for earth dams. In this context, this study presents an ANN model which allows the user to get four factors of safety (FS(i)) of small earth dams under long-term stability condition with static or earthquake loading immediately. Safety factors (FS(i)) for the model are calculated by carrying out two computations each for two cases, that is, earth dam subjected to full reservoir steady-state seepage condition with and without earthquake (FS(F + EQ) and FS(F)) and earth dam empty reservoir with and without earthquake (FS(Em + EQ) and FS(Em)). A database of 1372 different inputs and 4 outputs was built through strength reduction finite element method (SR-FEM). The used ANN is a feed-forward back-propagation neural network (FBNN) with three layers. The most appropriate FBNN architecture was found 11–21–4, as this gave the best FS(i) prediction with the lowest error. The relative importance of the inputs parameters is studied using both Garson’s algorithm and connection weight approach. Moreover, for further verification, the developed model has been used for prediction FS(i) of new earth dam datasets. The predicted results have been compared with the obtained ones from different limit equilibrium (LE) slope stability computations. The comparison had confirmed a very satisfactory capability of the ANN model to predict the FS(i).

Improvement of Engineering Properties of Residual Soil of Tuff Breccia by Electro-Kinetic Method

This paper presents the results of an experimental study that was conductedto improve engineering properties of residual soil of tuff breccia by applying the electrokinetic method. The soil samples were taken from a slope in a high susceptible landslide area in the Kulon Progo, Yogyakarta, Indonesia. The electro-kinetic experiments were conducted using a clear glass tank of 60 cm 30 cm 30 cm size, a 13 V power pack to supply the voltage, and aluminum electrodes. The results showed that the pH value of anolyte decreased while that of catholyte increased during the treatment. The Atterberg’s limits of all soil samples decreased, while the shear strengths increased. XRD and SEM analyses indicated that there were no mineral changes after electro-kinetic experiments. However, the soil structure changed and became denser. The increased soil strength after electro-kinetic treatment would likely improve stability of natural slopes.

THE LANDSLIDE HAZARD MAP OF BOGOTA AN UPDATING

Abstract. A land management plan (Plan de Ordenamiento Territorial, POT) is an instrument for planning the land-use of a territory considering physical, social and economic aspects. In the frame of the POT’s upgrading, the risk management plays an important role in conservation of human lives, prioritization of territory’s land-use as well as the formulation to reduce the fiscal vulnerability of the territorial institutions when a disaster occurs e.g. landslides. Landslides represent a rampant danger in Bogota’s hillside area because of accelerated urban growth, steep topography, degraded rocks, susceptible soils and abundant rain among other factors. It is calculated that more than 3 500 000 people live in such risky zones. This paper presents the methodology followed to update the landslide hazard map – from the GIS techniques perspective – produced by an interdisciplinary team formed by geologists, geotechnical and GIS specialists. The methodology used to obtain the map of landslide hazards consists of the combination of two partial results regarding to the evaluation and analysis of slopes’ stability in the studied area. The first one has to with a heuristic method that combines the variables prone to influence the occurrence of landslides. The following eight variables were included: relief, drainage, and material, land use as susceptibility factors and erosion, climate, earthquake, human factor as triggering factors. To combine these variable map algebra was used. While the second partial result involves stability of natural slopes. Despite the fact that in Latin-American region and especially in public institutions proprietary software is widely used, the visualisation and edition of geographic information was performed with QGIS software. Additionally, the study area covered a considerable part of Bogota’s urban region which demanded a quite efficient and robust software that allow to execute a straightforward and complex processing. GRASS GIS software was used to carry out most of the geoprocessing tasks without splitting up the datasets. The Open Source GRASS yielded excellent results proving be an efficient tool when dealing with big datasets. Furthermore, in the study of some variables very specific geomorphology algorithms, such as Terrain Classification from SAGA GIS, were used. Meanwhile automation of some geoprocesses was implemented with proprietary software. New techniques and procedures as well as detailed inputs with further level of detail provided a more accurate map in a shorter period of time. One of this techniques is the delimitation of areas for evaluating the stability of natural earth slopes which was analysed with the support of hydrological modelling in GIS. This helped to guarantee the homogeneity of these regions, yielding quite acceptable results when accuracy is proved as an important condition in the application of this method. This map constitutes a valuable input in the risk management when dealing with land planning of the city. From this new hazard map, new suitable areas for housing can be defined. Also, it is the initial input for determining the necessity of new civil works for disaster mitigation. In some cases, resettlement of affected people will be recommended when the levels of landslide’s hazards are not capable of being mitigated.

Recent landslides in North Cyprus

AbstractLandslides occur when the driving force overcomes the resistance from the shear strength of the soil along the rupture surface. A portion of a hillslope becomes too weak to support its own weight and moves down a slope. Landslides are most common on moderate to steep slopes. The causes of landslides include rainfall, earthquakes, volcanic eruptions, fires, loud sounds, and various human modification of the land, that disturb natural slope stability. Landslides commonly occur with floods and earthquakes and constitute a major natural hazard. A large part of Cyprus is covered by clayey soils. Landslides occur at the steep and very steep slopes of these formations. The high elevation areas of south west South Cyprus has a long history of slope instability. Large even massive scale landslides occurred in the inland parts of Paphos district. Recent Landslides in North Cyprus due to new road construction indicates that the new development areas also need to be investigated more careful.

A Comparison Study between Traditional and Finite Element Methods for Slope Stability Evaluations

ABSTRACT Landslides are amongst the major disasters that have occurred in Karabük, Turkey. Due to the rapid increase in population movement to new habitats in urban areas, the need for engineering structures will increase. This condition has led to the construction of arts, cultural facilities and housing in insecure regions these days. The excavations to prepare the construction site, the external loads due to heavy structures and the changes in coverage of the earth surface are among the reasons for landslides in such areas. In this study, the landslides that occurred due to unsupported excavation for the construction of Karabük university stadium were analyzed using the three softwares like Plaxis, Geoslope and Slide. The study area is critical in terms of slope problems. Mass movement in the stadium occurred in high plasticity clay units containing sand and silt. For this reason, it is necessary to carry out detailed studies before the construction of engineering structures. The landslide considered in the study were analyzed using finite element (FE) analysis and slice method. These approaches are used for evaluating the stability of natural slope by considering a failure mechanism, which is known as the plastic limit condition. Regarding safety factors calculated using the different numerical solutions confirm that the results obtained are similar. In addition, the landslide area is close to the predicted simulation results.

Evaluation of the influence of climatic and geomorphological factors on landslides development

The paper deals with the study of factors influencing the propagation of landslides in Ukraine. According to numerous monitoring studies, climate changes have significant impact on the stability of natural slopes and cause landslide processes. The topicality of the study is connected with the multifactor mechanism of landslides formation and complexity of this process development in space and time scales. Activation of landslides is registered on the territory of almost all administrative regions of Ukraine. The increasing dependence of the number of recorded landslides on annual precipitation and relief is established. For the most landslide-prone regions of Ukraine, the integral coefficients of the relief influence have been calculated, and the levels of potential landslide risk have been determined. Linear regression dependence between the amount of atmospheric precipitation and the number of landslides has been obtained, which allows predict landslide hazard in the regions of Ukraine. The results of the calculations are presented graphically in the form of a map.

Understanding Constraints and Triggering Factors of Landslides: Regional and Local Perspectives on a Drainage Basin

The Grande da Pipa River (GPR) basin (Portugal) has natural conditions that favor the occurrence of landslides. The hydrological year 2009/10 was characterized by high amounts of rainfall, which led to the occurrence of an also high number of landslides in this basin. The hydrodynamic character of the GPR basin was analyzed through a lumped parameter model of daily sequential water balances, in order to understand its influence in the stability of natural slopes. Results from the model were confronted to the inventory of landslides that occurred in the basin during the hydrological year 2009/10. Morphological, geotechnical, and hydrological local conditions affecting slope stability were also analyzed through back-analyses of two selected deep-seated landslides. Data here presented shows that the rise of water table is an important triggering factor for landslides. The most important constraint for landslides in the area is the degree of weathering and thickness of the upper layer of degraded marls. In most of the basin, the degraded layer is less than 5 m deep, causing the occurrence of shallow and intermediate landslides. However, deep-seated landslides were also found in areas, even with degraded marls that were less than 5 m-thick, where landslides have also occurred in the past.

Influence of Failure Probability Due to Parameter and Anchor Variance of a Freeway Dip Slope Slide—A Case Study in Taiwan †

The traditional slope stability analysis used the Factor of Safety (FS) from the Limit Equilibrium Theory as the determinant. If the FS was greater than 1, it was considered as “safe” and variables or parameters of uncertainty in the analysis model were not considered. The objective of research was to analyze the stability of natural slope, in consideration of characteristics of rock layers and the variability of pre-stressing force. By sensitivity and uncertainty analysis, the result showed the sensitivity for pre-stressing force of rock anchor was significantly smaller than the cohesive (c) of rock layer and the varying influence of the friction angle (ϕ) in rock layers. In addition, the immersion by water at the natural slope would weaken the rock layers, in which the cohesion c was reduced to 6 kPa and the friction angle ϕ was decreased below 14°, and it started to show instability and failure in the balance as FS became smaller than 1. The failure rate to the slope could be as high as 50%. By stabilizing with a rock anchor, the failure rate could be reduced below 3%, greatly improving the stability and the reliability of the slope.

Spatial variability analysis of soil strength to slope stability assessment

Uncertainty is a fact belonging to engineering practice. An important uncertainty that sets geotechnical engineering is the variability associated with the properties of soils or, more precisely, the characterization of soil profiles. The reason is due largely to the complex and varied natural processes associated with the formation of soil. Spatial variability analysis for the study of the stability of natural slopes, complementing conventional analyses, is able to incorporate these uncertainties. In this paper the characterization is performed in back-analysis for a case of landslide occurred to verify afterwards the presence of the conditions of shear strength at failure. This approach may support designers to make more accurate estimates regarding slope failure responding, more consciously, to the legislation dispositions about slope stability evaluation and future design. By applying different kriging techniques used for spatial analysis it has been possible to perform a 3D-slope reconstruction. The predictive analysis and the areal mapping of the soil mechanical characteristics would support the definition of priority interventions in the zones characterized by more critical values as well as slope potential instability. This tool of analysis aims to support decision-making by directing project planning through the efficient allocation of available resources.

Long-term investigations on the pore pressure regime in saturated and unsaturated sloping soils

Pore pressure changes play a major role in the stability of natural slopes, whose safety factor value is usually much smaller than that generally accepted in any other geotechnical problem. Correct assessment of potential seasonal pore pressure distributions is therefore a crucial issue in slope stability analysis. Based on long-term monitoring of some natural slopes, this paper compares the pore pressure distribution recorded in saturated fine-grained deposits and in shallow unsaturated granular covers, both monitored in southern Italy. In spite of the expected differences, the soils display some common features. In particular, from December to mid-May (wet period) in all examined cases the pore water pressures are quite constant over a monthly scale. Thus an essentially steady-state pore pressure condition establishes. It is in this phase, which is characterised by an essentially downward flux, that the safety factor drops to its lowest yearly value. Finally, a simplified method is adopted to model the steady-state pore pressure during the wet period and to calculate the average rain infiltration in equilibrium with the steady-state condition; the results thereby obtained are compared with the findings of an advanced approach, based on the hydrological balance.

PERKUATAN LERENG DENGAN GEOGRID DAN SHEET PILE PADA JALAN KIKIM BESAR (KM. 256) KOTA LAHAT

Landslide is one of the most common problems in improving road structures. One of the landslide cases occurred in the area of Kikim Besar, Lahat District precisely at Km.256. To obtain an optimal solution of the problem requires proper analysis in the reinforcement of the slope. In this study used an alternative slope reinforcement by using sheet pile or geogrid reinforcement. The purpose of this research is to know the condition of natural slope stability at that location and the effect of stability slope change with retrofitting structure using sheet pile or geogrid. This research uses modeling with Plaxis 2D program. Modeling was made to obtain the safety factor values on the natural slopes on the slopes 1-1, 2-2, and 3-3 pieces, comparing the safety factor of each slope before and after the reinforcement, and comparing the safety factor of each slope after reinforcement using geogrid type UX 1700 and sheet pile type W325 A 1000. From the research results obtained that the strengthening of geogrid and sheet pile can increase the value of slope safety factor. The sheet pile modeling has the greatest safety factor value for each slope of 1.794 for slopes 2-2 and 1,532 for slopes 3-3 compared with geogrid reinforcement that produces a safety factor value of 1,325 for slopes 2-2 and 1,343 for slopes 3-3 pieces.