Cause Of Slope Failure Research Articles

Discrete-element method simulations of shallow landslides triggered by rainfall

Rainfall infiltration is a primary cause of slope failure. Analyzing the entire process of a landslide triggered by rainfall is crucial for the design of infrastructure. However, the complexity associated with simulating large deformations has often hindered previous studies from modeling the entire landslide process subsequent to rainfall infiltration. This study aims to provide a method to simulate the entire process of landslides considering rainfall and more insight into the mechanism of landslides. The discrete element method (DEM) is first applied to model the entire process of shallow landslides triggered by rainfall. The numerical results indicate that the intensity and duration of rainfall infiltration have significant impacts on the slope stability. The particle displacement field, resulting from landslides due to rainfall, corresponds with three distinct stages within the landslide process. The increased rainfall intensity causes the area of the particles within failure mass grows rapidly during the initial stage of the landslide. The closer to the slope surface the faster the particle velocity. The simulations demonstrate that the slope surface transitions from a linear to a concave downward geometry during the landslides. Larger particles display greater displacement and velocity compared to smaller particles.

Consequences of slope instability and existing practices of mitigation in hydropower projects of Nepal

IntroductionNepal has witnessed several instances of slope instability associated with Hydroelectric Projects in the recent decades. Despite this, slope instability tends to receive less attention compared to other hazards.ObjectivesThe objective of this study is to investigate fourteen hydroelectric projects with the aim of identifying the types and causes of slope failures. Additionally, it seeks to offer a comprehensive understanding of slope stability conditions and challenges encountered during construction at project sites.MethodsTo accomplish this, the study employs Key Informant Interviews with Questionnaires to delve into the slope stability concerns within Nepal’s hydropower projects. The findings are then validated through an extensive review of pertinent literature. To conduct a thorough assessment of slope stability, the study relies on on-site observations, measurements, investigations, and both in-situ and laboratory tests.ResultsIt becomes evident that the careful selection of study sites, the application of geotechnical methods, and the establishment of regular monitoring are pivotal for ensuring favorable slope stability outcomes.ConclusionA majority of respondents concur that cutslope is the primary factor causing slope instability with 44.4% answering affirmatively. An independent t-test reveals there is no significant difference between the variables. Moreover, the correlation which is closed to 1 suggests that perception of respondents are interconnected and tend to vary in a synchronized manner. Participants in the study widely acknowledge numerical modeling methods as a means to overcome the limitations of slope stability studies.

Artificial Neural Network Model to Predict the Factor of Safety in Earth Dams Subjected to Rapid Drawdown

Rapid drawdown has been identified as one of the most frequent causes of slope failures due to the effects associated with drought and operational changes when incorporating hydroelectric plants, which influence the filling level of earth dams. The main goal of this research is to obtain predictive models based on Artificial Neural Networks that return the factor of safety of the upstream slope in homogeneous earth dams in the face of the effect of rapid drawdown. Three geometries and 40 soils were defined to form the embankment, from which hybrid numerical models of transient water flow with unsaturated soils were built, considering three discharge speeds. From these results, a database was built to develop the predictive models, by means of the KNIME program and an algorithm based on Artificial Neural Networks. The behavior of the factor of safety as a function of time is also analyzed to establish its recovery intervals. Main results show that the minimum factor of safety is obtained between 52 % and 88 % of the total drawdown time. Regarding the predictive models, the adjusted R2 determination coefficients were greater than 95 % in all cases and the errors remained below 10 %. This demonstrates a high effectiveness of this algorithm and the validity of its application to geotechnical problems.

Evaluasi Faktor-Faktor Penyebab Longsor dan Kesesuaian Mitigasi

Management and maintenance of slopes require proper knowledge of slope conditions so that appropriate mitigation measures can be implemented. The activities required for the management of slopes include slope inventory, slope inspection, slope risk level assessment, and risk mitigation measures. The objective of this study was to observe the slope conditions and causes of past slope failures, determine the appropriate mitigation measures, and analyze the suitability of landslide mitigation measures and causes of slope failures. The research locations are road segment No. 36 (Kota Lahat – Simpang Air Dingin), No. 37 (Simpang Air Dingin – Pagar Alam), and No. 38 (Pagar Alam – Tanjung Sakti – batas Bengkulu). The research was initiated by analyzing data collected by the South Sumatra National Road Management Agency (BPJNSS) from 2018 to 2021. The field observation was conducted on ten locations where the slope had been repaired after slope failure events. The suitability of mitigation with the factors that cause landslides was analyzed using the slope management system method suggested by the Ministry of PUPR. The results showed that most slope failures were triggered by high-intensity rain falling on slope surfaces containing high humidity due to previous rainfall. The common types of slope mitigation are reducing the forces that cause movement, increasing the resisting forces by controlling seepage, and the use of anchors.

Reliability of Municipal Solid Waste Landfills within the Eurocode Framework

Municipal solid waste (MSW) landfill slope failures can have significant consequences for the economy, environment, and human health. One potential cause of slope failure is insufficient reliability, resulting from inadequate design. The usual practice in the design of MSW landfills involves utilizing established geotechnical codes, such as Eurocode 7 (EC7), to perform slope stability assessments. Considering the substantial heterogeneity of MSW relative to soil, questions arise regarding the justification of such an approach in the design of MSW landfills. This study examines the suitability of applying EC7 in MSW landfill design, analyzing the stability and reliability of landfill slopes across various heights, front slope angles, design approaches, and consequence classes. This study finds that, in most cases considered, EC7 does not ensure an adequate level of reliability for MSW landfill slopes. Therefore, it is suggested that EC7 should be complemented with specific guidelines for incorporating MSW in geotechnical analyses to achieve the desired structural reliability. Adopting this strategy will not only enhance the reliability of landfill design but also promote the development of solutions that are economically and environmentally sustainable.

Back Analysis and Potential Remedial Approach for Failure Slope at Bukit Nanas, Kuala Lumpur

This study aims to validate the design parameters and stability of the slopes failure and propose acceptable remedial work by assessing the slope stability in Bukit Nanas, center of Kuala Lumpur. The slopes’ height is around 40 and 60 m with the gradient around 30°-45°. Totally 7 boreholes be carried out and the pertinent engineering properties were analyzed from laboratory testing and back analysis (in situ test). An established computer program SLOPE/W was used to carry out for slope stability analysis. The analysis method adopted was Morgenstern-Price’s Method. Based on the result of the field investigation and numerical analysis, the model of lowest factor of safety (FOS) that evaluated from the existing slope in critical section were selected and recommended for remedial work. Two option of remedial slope design had been proposed. The first option is soil nailing with grid beam and proposed drain while the second option is hybrid anchor with grid beam and proposed drain. Both options are used to improve the slope stability, but first option had been chosen as higher FOS and more efficient option. This remedial approach based on the main cause of slope failure in Malaysia can applied as reference in future slope remedial design.

Assessment of slope-cut landslides along Pokhara-Baglung Highway, Nepal

The study addresses the ramifications of development initiatives in delicate mountainous terrains, unveiling significant economic constraints and multifaceted environmental challenges. It focuses on investigating substantial landslides triggered by excavations along a specified stretch of Nepal's Pokhara-Baglung Highway. This research holds significance for policymakers engaged in devising highway development strategies that mitigate future landslides, minimizing both costs and the toll on life and assets. The investigation encompassed on-site cataloging of landslides, lab test of sampled soils and a structured questionnaire distributed among local residents. This comprehensive approach facilitated a thorough assessment of landslide occurrences and their consequential effects. The identified landslides exhibited a consistent rotational pattern, characterized by abundant quartzite and phyllite rock formations. The predominant soil composition consisted of fine-to-medium sands, exhibiting a Plasticity Index (PI) range of 0.5 to 3, indicating marginal plasticity. Significantly, a substantial portion (70%) of the populace reported tangible impacts from landslides, with about 32% of affected individuals confirming an average agricultural productivity loss of 4330 kg/km2. Statistical analysis using the Chi-square test indicated a uniform impact across various demographic categories, including gender, education, proximity to the affected site, and social caste. Although fluctuations in the region, the observed temporal precipitation consistency over decades suggests as an accelerating rather than primary causative factor for landslides. Thus, principal causes of slope failures predominantly link to inadequately managed bedrock excavations and suboptimal road drainage systems underscoring the necessity for systematic inquiries into soil stability post-slope incisions. These measures are pivotal in guiding the construction and expansion of road networks within Nepal's Himalayan region.

Multiscale modeling of seepage-induced suffusion and slope failure using a coupled FEM–DEM approach

Suffusion refers to the detachment and migration of fine particles through voids among coarse particles and is one of the major causes of slope failure. This study investigates the seepage-induced suffusion and slope instability using a hierarchical multiscale finite–discrete element method (FEM–DEM). An erosion law with the critical hydraulic gradient for the onset of suffusion is proposed. Two examples, including one-dimensional suffusion and biaxial compression tests, are performed to verify the proposed scheme. Emphases are placed on reproducing suffusion and progressive slope failure process under seepage flow. The results indicate that a shear band is initiated from the slope toe and gradually extends to the crest. The increase of erosion rate accelerates the process of suffusion and slope failure, whereas a higher critical hydraulic gradient plays an opposite role. In addition, fines loss caused by suffusion occurs mainly on the slope surface, especially near the slope toe. Microscopic analyses on locally embedded representative volume elements (RVEs) indicate that RVEs inside the shear band experience severe deformation and microstructural changes, manifested by the rearrangement of soil skeletons and variation of contact force chains.

Climatic Influence on Slope Failure: A Case Study at Kem Terendak, Melaka

Slope failure or landslide is always ascribing to the slope sculptures in the hilly area. The trend of people building a structure on a hilly area has resulted in slope cutting works being carried out aggressively and, at the same time, has increased the risk of landslides. Most of the community lacks understanding regarding slope care and maintenance, which adds to the slope suffering. One of the factors contributing to slope failure is rainfall. The rainfall-runoff to the slope erodes the turfed and topsoil particles from the slope surface. When the slope surface is exposing to extreme weather, then the slope failure will occur. These failures pose a significant engineering hazard, necessitating urgent repair work and planning in many areas. All failures that occur will require expensive repairing costs. Therefore, this study is carried out to model the rainfall-induced slope failure occurrence at Kem Terendak, Melaka. This study utilises a simulation of slope stability analysis by limit equilibrium, Slope/W 2012 and finite element software for simulating groundwater flow in saturated steady-state situations, Seep/W 2012 in order to analyse the stability of the slope with the influence of climate. Through those analysis, one can understand the causes and mechanisms of the landslide. At the same time, the factors that influence the occurrence of failures can be identified and appropriate action can be taken to reduce or even eliminate the root cause of slope failures. In addition, effective and efficient slope repair methods can be proposed with optimal cost.

Analysis of the slope failure mechanism a under tunnel erosion environment in the south-eastern Loess Plateau in China

As a unique geological hazard, the occurrence of loess tunnels is closely related to slope failures. However, almost no research on the relationship between loess slope failures and tunnel erosions has been presented, which seriously restricts the deep understanding of the genesis mechanism and evolution process of loess slope failures. This paper focuses on revealing the failure mechanism of loess slopes in tunnel environments via methods including field investigation, exploration, field water injection tests, tracking tests and numerical simulations. The results show that the whole process of permeability coefficient of the soil layer in the test site is divided into three stages: the rapidly decreasing stage, the slowly decreasing stage and then the stable stage; the slope failure process is divided into five stages based on different failure characteristics: the soaking and softening stage, the erosion connecting stage, the slope local failure stage, the slump failure stage and the resting stage. Seepage has a great influence on loess slope failures in the tunnel environment, and it is as an important inducement of failure, while tunnels themselves play an aggravating catalytic role. The soil water interaction is shown to be an important internal cause of slope failure both by field tests and numerical simulations. The existence of tunnels is not conducive to the overall stability of the slope as tunnels expand the influence range of the soil-water interactions. This study re-evaluates the failure mechanism of loess slopes from a novel perspective based on the tunnel erosion environment.

Study on instability and damage of a loess slope under strong ground motion by numerical simulation

The instability and damage of loess slopes under strong ground motion can be a complicated process, involving sliding, translation, and rotation, which makes the discrete element method as a suitable theory to simulate such a process. Therefore, in this study, the particle flow code (PFC) is developed to simulate the instability and damage process of the loess landslide under strong motion. Based on field investigations and laboratory tests, the detailed identification of mesoscopic parameter was calibrated, and a 2D model was established. The results show that the slope surface tends to amplify the ground motion, resulting in the strong vibration of the soil on the slope surface. The slope shoulder is the position with the largest amplification coefficient of seismic acceleration, which is the key to the instability and failure of the slope. And, under the seismic force, the tensile failure firstly occurs in the slope upper part, and then the accumulation failure occurs in the lower part, finally a shear outlet is formed. Accordingly, high-frequency component of the Fourier spectrum increases with the slope failure. This study highlights the gradual increase in the difference between the first principal stress and the third principal stress, which destroys the inherent cohesive cements between particles, which is the main cause of slope failure under strong motion.

Forensic Analyses and Rehabilitation of a Failed Highway Embankment Slope in Texas

A comprehensive investigation was designed and conducted to identify the potential causes of failure of a highway embankment slope in Texas and evaluate the effectiveness of lime treatment to rehabilitate the failed slope. Highway slopes built with high plasticity clays often experience shallow slope failures after exposure to repeated wet–dry weathering cycles. Lime stabilization generally reduces the swell–shrink potential, enhances the engineering properties of problematic clayey soils, and can potentially prevent surficial slope failures. However, exposure to wet–dry cycles can negate some of the benefits of lime treatment and therefore a study was conducted to address the use of this lime treatment to stabilize embankment slopes. Extensive laboratory tests were conducted to study the effect of weathering cycles on the degradation of hydro-mechanical properties of untreated and lime-treated soils. Rainfall-induced slope stability analyses were performed to investigate the probable causes of slope failure and evaluate the stability of lime-treated surficial slope. The optimum stabilizer dosage and treated layer thickness required for the slope rehabilitation were determined based on laboratory tests and numerical analysis results. The stability analysis results indicate that the degradation of surficial soil’s hydro-mechanical properties and the development of a perched water table during prolonged rainfall possibly caused the slope failure. The post-treatment increase in shear strength properties, reduction in moisture fluctuations recorded by embedded moisture sensors, and the presence of newly installed underlying drains are expected to prevent recurrence of surficial slope failures. Salient results from this study are covered in this paper.

A method for seismic stability analysis of jointed rock slopes using Barton-Bandis failure criterion

Earthquakes are the main cause of slope failure in seismic active regions. In this study, we present a method for analyzing the seismic stability of a plane jointed rock slope with two blocks. In this analysis, the Barton-Bandis failure criterion is applied, considering the nonlinear characteristics of rock joints. Based on the limit equilibrium principle, we derived the safety factor of a jointed rock slope subjected to the modified pseudo-dynamic seismic forces. In addition, the analytical method developed in this study explains the interaction force between two blocks. Hence, it can effectively analyze the stability of a jointed rock slope and distinguish the failure modes. Further, a parametric study was conducted to investigate the effects of geometric and material properties on the safety factor of a hypothetical slope. The results show that the slope stability is significantly influenced by the geometry of the slope and the parameters including the joint roughness coefficient JRC, the horizontal seismic acceleration coefficient kh, the joint compressive strength JCS, and the basic friction angle of the structural plane ϕb. Moreover, the accuracy of the derivation is verified by the universal distinct element code UDEC 6.0. A parametric sensitivity analysis is used to determine the key parameters affecting slope stability. Finally, a set of seismic stability design charts is produced for preliminary design.

Identification of landslide-prone slopes at Paglajhora area, Darjeeling Himalaya, India

Paglajhora area, located in the southeastern part of the Kurseong town in the Darjeeling Himalaya region, India, experiences frequent slope failure especially in monsoon season. Due to the intricate disposition of major thrust zones (MCT, MBT, etc.), heavy rainfall, neotectonic and anthropogenic activities, etc., the cause of slope failure is not similar all over the area, which makes difficult to categorize the landslides based on their mode of failure. The present work is aimed to demarcate the landslide-prone areas from the surface displacement (horizontal) map derived by optical image correlation (OIC) technique applying normalized cross-correlation (NCC) algorithm of two temporal Landsat 8 OLI (level 1TP) images, supported by the ground field survey. Results indicate that the overall range of surface displacement (horizontal) rate in the study area varies from 0.4 to 8 m/year out of which the range 0.5–1.5 m/year being dominant classifying the slide type as slow-to-very slow earth flow with a velocity class varying from 3 to 2. Places showing relatively higher displacement values (3 to 8 m/year) match accurately with the already reported slide zones and the large exposed scarp surfaces noticed during the field surveys or distinguished from the satellite imagery. Areas with lower displacement rates (< 1.5 m/year) experience very slow earth flow, which are confirmed by the presence of cracks and steps on the major roads. Depths of shallow subsurface slip planes are established from dipole-dipole geo-electric surveys in few locations showing moderate surface velocity.

Using the GNSS method assisted with UAV photogrammetry to monitor and determine deformations of a dump site of three open-pit marble mines in Eliktekke region, Amasya province, Turkey

The determination and monitoring of deformations that may occur in the benches of dump sites of open-pit mines are important for both security and continuity of mine production. The Global Navigation Satellite System (GNSS) is the most preferred method for deformation monitoring at dump sites. While the amount of deformation (3D displacements) can be determined at the points monitored by the GNSS method, interpretations on the cause and/or areal size of the deformation may remain limited. The main factors or triggering causes of slope failures at dump sites are base topography, geometric dimensions (width, height, and slope) of the formed benches, stiffness ratio of the dumped material, and load increases caused by new dumps in the lower benches. In this study, UAV photogrammetry and GNSS were used together, and the deformations at the adjacent dump site of three different open-pit marble mines located in Eliktekke region of Amasya province in Turkey were monitored. The GNSS method determined the points where displacements occurred, and the UAV photogrammetry searched for the causes of mobility at the point and its areal and volumetric sizes. The UAV photogrammetric results revealed that the topographic slope and overall slope inclination triggered the movement of the zones. Field measurements and evaluations made for this dump site showed that the current geometry should be kept where the overall slope inclination reaches 14° and not to be increased further. The results support that the GNSS method assisted with UAV photogrammetry is a rapid and economical method to determine both the borders and volumetric sizes deformations as their causing parameters. Through the proposed methodology, it will be possible to effectively determine the main factors causing slope failures in similar areas and to take the necessary measures on time.

Determination of Empirical Rainfall Thresholds for Shallow Landslides in Slovenia Using an Automatic Tool

Rainfall-triggered shallow landslides represent a major threat to people and infrastructure worldwide. Predicting the possibility of a landslide occurrence accurately means understanding the trigger mechanisms adequately. Rainfall is the main cause of slope failures in Slovenia, and rainfall thresholds are among the most-used tools to predict the possible occurrence of rainfall-triggered landslides. The recent validation of the prototype landslide early system in Slovenia highlighted the need to define new reliable rainfall thresholds. In this study, several empirical thresholds are determined using an automatic tool. The thresholds are represented by a power law curve that links the cumulated event rainfall (E, in mm) with the duration of the rainfall event (D, in h). By eliminating all subjective criteria thanks to the automated calculation, thresholds at diverse non-exceedance probabilities are defined and validated, and the uncertainties associated with their parameters are estimated. Additional thresholds are also calculated for two different environmental classifications. The first classification is based on mean annual rainfall (MAR) with the national territory divided into three classes. The area with the highest MAR has the highest thresholds, which indicates a likely adaptation of the landscape to higher amounts of rainfall. The second classification is based on four lithological units. Two-thirds of the considered landslides occur in the unit of any type of clastic sedimentary rocks, which proves an influence of the lithology on the occurrence of shallow landslides. Sedimentary rocks that are prone to weathering have the lowest thresholds, while magmatic and metamorphic rocks have the highest thresholds. Thresholds obtained for both classifications are far less reliable due to the low number of empirical points and can only be used as indicators of rainfall conditions for each of the classes. Finally, the new national thresholds for Slovenia are also compared with other regional, national, and global thresholds. The thresholds can be used to define probabilistic schemes aiming at the operative prediction of rainfall-induced shallow landslides in Slovenia, in the framework of the Slovenian prototype early warning system.

Study on response characteristics of red clay slope under evaporation rainfall condition

Evaporation rainfall is one of the main causes of slope failure. Red clay belongs to special soil, and the failure mode of the slope is different from that of the general soil slope. In this paper, based on the theory of similarity simulation, a test model of red clay slope similar to the prototype is established in a certain proportion. Sensors are embedded in different positions of the slope to carry out the change rule of physical and mechanical indexes of the red clay slope under the condition of evaporation and rainfall. The results show that the water content of the slope increases during the rainfall period, the surface water content of the slope is obviously affected by the rainfall intensity, and the water content of the slope decreases in the drying period. Under the action of evaporation and rainfall, the internal temperature of slope is stable, and the surface temperature changes significantly. The pore water pressure of the top, shoulder and slope changes little with the times of evaporation and rainfall, and the pore water pressure at the foot of slope is obviously affected by evaporation and rainfall. Evaporation rainfall causes obvious horizontal displacement of red clay slope. The earth pressure increases in the rainfall period and decreases in the static and dry periods. With the increase of evaporation rainfall times, the earth pressure increases gradually.

Efficient probabilistic back analysis of spatially varying soil parameters for slope reliability assessment

The probability distributions of soil parameters can be updated with limited site-specific information via probabilistic back analyses. The updated probability distributions can be further used for a more realistic slope reliability assessment. However, few attempts have been made to conduct probabilistic back analyses accounting for the inherent spatial variability of soil properties. The main challenge is the so-called curse of dimensionality encountered when thousands of random variables are used to model spatial variability. The BUS approach (Bayesian Updating with Structural reliability methods) can tackle the high-dimensional back analysis problem by transforming it into an equivalent structural reliability problem, but it requires an evaluation of the likelihood multiplier that is tedious and time-consuming. This paper proposes a modified BUS approach for the probabilistic back analysis of soil parameters and reliability updating of slopes in spatially variable soils. With this approach, the curse of dimensionality and evaluation of the likelihood multiplier can be effectively avoided, and the computational accuracy is significantly improved. Two slope examples are investigated to illustrate the effectiveness of the proposed approach. The soil parameters and their probability distributions for a slope section can be well determined through a probabilistic back analysis, which facilitates an accurate identification of the causes of slope failures and a deep understanding of the actual performance of in-service slopes.

Modelling the Stability of the Aleksotas Hill Slope in Kaunas

Main causes of slope failures in soils are: geological activities (earthquakes), hydrological influence (rise of the groundwater table), topographical features, weathering processes (a rainy season, snowmelt), human activities (vibrations from explosions, machinery, road and air traffic, loading the slope crest, etc.) and vegetation and climatic conditions. As a result, the shear strength of the soil decreases and factor of safety of the slope reduces to a low value that may trigger failures. The slope of the Aleksotas Hill was sliding in 2015. To protect the slope from future landslides, the reconstruction work began in 2018. Geotechnical modelling software SLOPE/W was used for determination of the factor of safety. Model with three modifications (variants) was created by SLOPE/W software for the slope behaviour modelling. The Aleksotas Hill slope stability calculations of original (natural) slope and excavated slope with constructing subsurface drainage was performed in order to evaluate the solutions proposed in the reconstruction project.

Slope failure in stratified rocks: a case from NE Himalaya, India

Mountainous regions of India experience recurrent slope failures due to rapid urbanization. The main causes of slope failure are high precipitation aided by unplanned construction of cut slopes. Such slope failures are further aggravated because of the presence of low strength, highly jointed, stratified rocks rich in clay minerals. In general, effect of weathering is more pronounced in these rocks, which causes long-term time-dependent deterioration of the rocks as well as joint strength. In this regard, the present investigation deals with the causes, behavior, and mechanism of slope failure by examining a section in the North Eastern Himalayas. A detailed field investigation was carried out for examining the existing condition of slope, slope material, and joint parameters. Laboratory experiments like compressive and tensile strength tests along and across the lamination planes along with slake durability index tests were conducted to characterize the material and investigate the role of weathering in strength degradation. Later, numerical simulation was performed employing distinct element method to investigate the failure behavior, mechanism, and also the effect of water pressure in destabilizing the slope. The experimental result indicates directional strength variations parallel and perpendicular to bedding plane, which makes the rock incompetent to sustain external load. The presence of orthogonal joint sets accelerates the process of block detachment. Significant slaking was observed which further deteriorates and fragments the rock at deeper level. Numerical simulation shows that failure plane is dominantly planar (along the bedding parallel joints) and surficial.