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Open-pit coal mining accounts for 93% of India's total coal production, playing a significant role in meeting the nation's substantial energy needs. The success of an open-pit mine hinges on maintaining the steepest and deepest slopes that remain stable over the mine's lifespan. However, slope failure is a complex issue influenced by numerous factors. In the context of openpit coal mines, the rise side highwall involves cutting through a rock mass containing various elements like an unconsolidated weathered mantle of sandstone, sandy clay, clay, carbonaceous shale and coal. Some opencast mines within the Godavari Valley Coal Field (GVCF), India have encountered significant pit slope failures. This paper uses a numerical modelling approach aimed at effectively assessing the stability of the rise side highwall, leveraging available geotechnical data from one of GVCF's largest opencast coal mines. The research investigates the impact of seven detrimental factors on slope stability, including dynamic loading due to blasting, employing a methodical One-Factor-At-A-Time (OFAT) approach. The study utilises Rocscience Phase2 version 9.0, a Finite Element Method (FEM) based numerical modelling software to gauge the sensitivity of each factor on the Factor of Safety (FoS). The numerical modelling results indicate that there is a linear decrease in FoS corresponding to the reduction in cohesion and an exponential increase in the FoS as the angle of internal friction rises. Furthermore, the analysis reveals significant impacts on the FoS due to groundwater and seismic loading from the blasting. This approach aims to comprehensively analyse and understand the intricacies of slope stability in the specific context of open-pit coal mining. [ABSTRACT FROM AUTHOR]

The paper describes the recent devastating landslide of Kotrupi, Himachal Pradesh in India which had claimed many human lives and properties along its course on 13 August 2017. This event was the third reactivation of the slide as per data available. The study for this landslide involves a preliminary investigation of the site and comparison of pre- and post-event slope stability analysis. Other than rainfall, the combined effect of differential weathering rate of the debris and soil layers, low material strength, and the presence of a fault zone was found to be the primary cause of instability. The analysis was carried out with the geotechnical investigation and numerical modeling with the help of finite element model-based Phase 2 simulator. The significant findings of this paper include numerical simulation of pre- and post-event slide as stated under unsaturated and saturated condition. The study finds a low factor of safety of the present slope. The unstable condition of the slope may trigger another event of the same intensity shortly. [ABSTRACT FROM AUTHOR]

In slope stability analysis, identification of the mechanism behind slope failure is the key factor during the study. Rock mass characterization and kinematics analysis, like geotechnical investigation methods, are not infallible all the time for the weathered slopes. The presence of different grades of weathered mass on the slope profile acts independently to influence the overall failure pattern. Numerical analysis by finite element method (FEM) is evolved as a primary slope stability analysis tool by overcoming the limitations of the stratified weathered materials on the slope. The paper focuses on the stability analysis of railway-cut laterite slopes of the Eastern Ghats of India. The medium to high-grade metamorphism, followed by physio-chemical weathering, favours the region for more prone to failure. The Force Equilibrium Model and Moment Equilibrium Model have been considered to determine the possibility of independent failure events for the probability analysis. Monte Carlo's probability simulation method has delivered a better result for the weathered slopes by taking many variables for the studied region. A compression study has been made between the outcomes of slope stability analysis methods and the probability analysis models, which provides a comprehensive list of factors to understand the failure mechanism of weathered slopes. [ABSTRACT FROM AUTHOR]

Evaluation of stability of artificial slopes created due to road construction in the mountainous terrain is very important but often a neglected aspect. The safe execution of road-cut slopes depends upon the level of understanding achieved in defining the engineering behaviour of rock masses with respect to its deformation and mechanical attributes. Understanding the realistic response of the rock mass to excavation of rock strata requires proper analysis related to influence of structural elements on their continuous characterization for facilitating safe and economical development of cut slopes along the road sections. In this paper structurally and non-structurally controlled rock slope classification systems are implemented to undertake comprehensive evaluation of stability of road-cut slopes. The work carried out involves collection of various inputs in form of rock mass and discontinuity characteristics from ten cut slopes along a road section in Kullu area, Himachal Pradesh, India. Rock samples were collected from site and laboratory testing has been undertaken to determine the intact rocks strength. Beside these, the kinematic analysis was performed to illustrate the geometrical relationship between various joint sets and the slope face so as to determine their failure mechanism. Several rock mass classification systems developed for rock slope stability assessment are evaluated for known slope conditions. The stability assessment for all identified cut slopes is compared using slope mass rating (SMR), Q-slope and slope stability rating (SSR) methods. Design charts proposed for various factor of safety values have been utilized to evaluate the stability of studied road-cut slopes. Finally, a slope wise comparison is made between the stable angles predicted by SSR with those recommended by Q-slope method. [ABSTRACT FROM AUTHOR]

This article presents the challenges encountered during the stability analysis and stabilization of two Himalayan rock slopes supporting the Chenab Railway Bridge in India, which will be the highest railway bridge in the world after completion. Owing to the importance of the project, extensive geological investigations, in situ and laboratory tests were carried out using conventional and advanced methods to evaluate various intact rock, rock joints, rock mass properties and rock mass quality present at the site. Once the conclusive results were made regarding these properties, stability of slopes were evaluated against both structurally controlled and stress-controlled failures using the developed probabilistic approach due to the presence of high variability in intact rock, rock mass and rock joints properties. It was observed that while the slopes were stable against stress-controlled failures, the possibility of structurally controlled failures exists as observed in the probabilistic approach in which the conventional deterministic approach was not able to detect. Different stabilization measures, i.e. rock bolts, slope flattening, grouting, drainage and shotcreting, were designed at the site to reduce the probability of failures for the slopes, deformability of rocks present due to cavities and high aperture joints, shallow block failures along the slope surface and pore-pressure build-up. To check the efficiency of the stabilization measures, cross-hole seismic tomography is carried out at the site and further in situ measured displacements are compared with the displacements estimated using the developed probabilistic approach. The case study used in this paper is a real-time ongoing bridge project of global interest and the data and analysis presented will be of great benefit to the researchers and practitioners working on similar problems. [ABSTRACT FROM AUTHOR]

Probabilistic methods are the most efficient methods to account for different types of uncertainties encountered in the estimated rock properties required for the stability analysis of rock slopes and tunnels. These methods require estimation of various parameters of probability distributions like mean, standard deviation (SD) and distributions types of rock properties, which requires large amount of data from laboratory and field investigations. However, in rock mechanics, the data available on rock properties for a project are often limited since the extents of projects are usually large and the test data are minimal due to cost constraints. Due to the unavailability of adequate test data, parameters (mean and SD) of probability distributions of rock properties themselves contain uncertainties. Since traditional reliability analysis uses these uncertain parameters (mean and SD) of probability distributions of rock properties, they may give incorrect estimation of the reliability of rock slope stability. This paper presents a method to overcome this limitation of traditional reliability analysis and outlines a new approach of rock mass characterization for the cases with limited data. This approach uses Sobol's global sensitivity analysis and bootstrap method coupled with augmented radial basis function based response surface. This method is capable of handling the uncertainties in the parameters (mean and SD) of probability distributions of rock properties and can include their effect in the stability estimates of rock slopes. The proposed method is more practical and efficient, since it considers uncertainty in the statistical parameters of most commonly and easily available rock properties, i.e. uniaxial compressive strength and Geological Strength Index. Further, computational effort involved in the reliability analysis of rock slopes of large dimensions is comparatively smaller in this method. Present study also demonstrates this method through reliability analysis of a large rock slope of an open pit gold mine in Karnataka region of India. Results are compared with the results from traditional reliability analysis to highlight the advantages of the proposed method. It is observed that uncertainties in probability distribution type and its parameters (mean and SD) of rock properties have considerable effect on the estimated reliability index of the rock slope and hence traditional reliability methods based on the parameters of probability distributions estimated using limited data can make incorrect estimation of rock slope stability. Further, stability of the rock slope determined from proposed approach based on bootstrap method is represented by confidence interval of reliability index instead of a fixed value of reliability index as in traditional methods, providing more realistic estimates of rock slope stability. [ABSTRACT FROM AUTHOR]

The geotechnical assessment, safe design and monitoring of highwalls is one of the major challenges in Indian open pit mines. The aim of opencast mines should be to attain steepest possible slope angle without compromising safety in order to maximize profits. Highwall stability is essential for economical and safe exploitation of mineral during open pit mining. Geotechnical investigations are required to quantify the properties of soils and rocks within the mining horizons. The required minimum safety factor for highwalls is 1.2. Highwall should be monitored during open pit operations. This paper addresses the main elements of pit slope failure, accident statistics, design, and monitoring and pit slope management and also the guidelines for safe design and monitoring of open pit highwalls in India. [ABSTRACT FROM AUTHOR]

Landslides are among the nature's primarily ways of adjustment to slope stability. In Darjiling Himalayas the process has been intensified by human interference mainly through rapid deforestation, incorrect construction procedure and unplanned tapping of natural resources. The present paper aims at investigating the occurrence of landslides mainly due to human intervention. For analyzing the acuteness of the problem, important events of landslides over time, landslide susceptibility map using traditional check-list and investigation of the nature of human intervention for landslide occurrences have been carried out. From the study it is found that extreme rainfall events of consecutive days accumulating an amount of 1000 to 1200 mm, coupled with deep weathering in susceptible structure could trigger to 5 to 10 m-thick landslides. Being saturated with percolating rainwater, such slopes even with a rainfall 50 of mm/h would cause disastrous landsllides. Common occurrence of landslides is found along the springs, where thick debris is removed along the slope, ontop of the bedrock. Generally deforested urbanized tracts, illegal coal mining sites, tea gardens, artillery roads connecting hills with the plains are the most susceptible areas to sliding. [ABSTRACT FROM AUTHOR]

The seismic slope stability analysis of the right abutment of a railway bridge proposed at about 350 m above the ground level, crossing a river and connecting two huge hillocks in the Himalayas, India, is presented in this paper. The rock slopes are composed of highly jointed rock mass and the joint spacing and orientation are varying at different locations. Seismic slope stability analysis of the slope under consideration is carried out using both pseudo-static approach and time response approach as the site is located in seismic zone V as per the earth quake zonation maps of India. Stability of the slope is studied numerically using program FLAC. The results obtained from the pseudo-static analysis are presented in the form of Factor of Safety (FOS) and the results obtained from the time response analysis of the slope are presented in terms of horizontal and vertical displacements along the slope. The results obtained from both the analyses confirmed the global stability of the slope as the FOS in case of pseudo-static analysis is above 1.0 and the displacements observed in case of time response analysis are within the permissible limits. This paper also presents the results obtained from the parametric analysis performed in the case of time response analysis in order to understand the effect of individual parameters on the overall stability of the slope. [ABSTRACT FROM AUTHOR]

• Extensive geotechnical characterization of the soil from landslide slip surface helps evaluate the failure mechanism of landslide. • High-intensity rainfall, unplanned vertical cuts and slopes have witnessed the loss of lives and substantial monetary losses during the southwest monsoon in Kerala, India, in 2018. • Importance of locally available sustainable green martial uses in engineering practices. • The numerical analysis confirmed that the vertical cut stabilization with coir geotextiles is safe during high-intensity rainfall. This paper presents laboratory and numerical analysis of vertical cut failure due to rainfall-induced landslide resulting in building failure that led to the death of nine people in Kerala, India, on August 15, 2018. The residual shear strength parameters are evaluated by the ring shear test. The soil water characteristics curve (SWCC) is developed by unsaturated soil strength parameters. The slope stability and infiltration analysis are carried out with limit equilibrium and finite element methods, respectively. The infiltration analysis is carried out by considering three different rainfall patterns on the slope as low, medium, and high intensities. The study includes a two-stage numerical analysis of vertical cut. Firstly, vertical cut analysis with and without rainfall effects and second, the analysis of vertical cut using coir geotextile as reinforcement with rainfall effects. The study emphasized the utilization of locally available coir geotextiles as a reinforcement for slope stabilization. [ABSTRACT FROM AUTHOR]

On 30th July 2014, a devastating landslide resulted in the burial of a village called Malin in western India and led to about 160 deaths. The catastrophic failure was triggered by heavy rainfall over the last 3 days. Site investigation was conducted to obtain representative information about the area. To understand the relevant physics, which initiated landslide, seepage and back analysis of the unsaturated slope was performed. Transient seepage analysis was carried out using finite difference method to simulate the slope behavior during rainfall infiltration. A coupled fluid flow analysis was employed to capture the fluid/mechanical interaction in unsaturated soils accurately. The results show that antecedent rainfall played a role in slope instability; rainfall intensity and duration also have a big impact on slope instability. This paper presents a methodology to back analyse the slope so as to identify the mechanisms responsible for landslide initiation. Back analysis is performed using a probabilistic method based on Bayesian analysis. Probabilistic methods can back-analyse numerous sets of uncertain slope stability parameters. The uncertain parameters are imported as random variables in the analysis and are described by their probability distributions. Bayesian analysis updates these distributions based on the observed slope behavior. The method evaluates the reduction in matric suction which initiated landslide in Malin slope. The results show that the decrease in matric suction of about 100% in addition to the development of positive pore pressures is the main mechanism which has triggered the landslide. This amount of reduction in matric suction and the development of positive pore pressures decreases the mobilized shear strength in soil below the threshold value required to maintain equilibrium in the slope and hence the slope failed. [ABSTRACT FROM AUTHOR]

Landslides may be caused either by natural process or human activity or combination of both. In many cases, modifications in hill slopes are carried out with or without proper slope stability analysis, even though the consequences are well known. In other cases, stable slopes are converted into unstable slopes by the people residing in the area by artificial modification/alterations of the hill slope without basic knowledge of hill slope management. Such cases are very common in the hilly terrain including northeast India and they have caused loss of many lives even though the size of such landslide are very small. The present paper describes four examples from different parts of the northeast India where the terraced hill slopes that remained stable for an appreciable length of time have been converted to unstable slopes. [ABSTRACT FROM AUTHOR]

Abstract: An earthquake of magnitude of 7.6 (M w 7.6) occurred in Bhuj, India on January 26, 2001. This event inflicted damages of varying extents to a large number of small to moderate size multi-zone earth dams in the vicinity of the epicenter. Some of the distress was due to the liquefaction of saturated alluvium in foundation. Liquefaction was relatively localized for the majority of these dams because the earthquake struck in the middle of a prolonged dry season when the reservoirs behind these dams were nearly empty and shallow alluvium soils underneath the downstream portions of the dams were partly dry. Otherwise, liquefaction of foundation soils would have been more extensive and damage to these dams more significant. Six such dams have been examined in this paper. Four of these facilities, Chang, Shivlakha, Suvi, and Tapar were within the 50 km of epicenter region. These dams underwent free-field ground motion with peak ground accelerations between 0.28g to 0.52g. Of these Chang Dam underwent severe slumping, whereas Shivlakha, Suvi, and Tapar Dams were affected severely especially over the upstream sections. Fatehgadh Dam and Kaswati Dam were affected relatively less severely. Foundation conditions underneath these dams were first examined for assessing liquefaction potential. A limited amount of subsurface information available from investigations undertaken prior to the earthquake indicates that, although the foundation soils within the top 2.0 to 2.5 m underneath these dams were susceptible to liquefaction, Bhuj Earthquake did not trigger liquefaction because of lack of saturation of these layers underneath the downstream portions of these dams. These dams were then analyzed using a simple sliding block procedure using appropriate estimates of undrained soil strength parameters. The results of this analysis for these structures were found to be in general agreement with the observed deformation patterns. [Copyright &y& Elsevier]