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Parametric Study of the Slope Stability by Limit Equilibrium Finite Element Analysis
Abstract
Slope stability analyses of both natural and artificial slopes are an issue and need to be taken care of as they can affect both economic and infrastructure development. Water is the main factor that often leads to slope instability. Numerous studies are available in this direction, and it shows that the presence of the water harms the shear parameter, and it should increase the groundwater table, which further leads to loss of shear strength. The slope’s stability depends on the shear parameter, cohesion, and angle of internal friction. If we can develop the relationship of this parameter with the instability, it can monitor the slope. This research’s prime objective is to analyze the effect of the different controlling parameters on slope instability. The stability analysis has been done through the limit equilibrium finite element slope stability model. The slope was modeled in the commercial package GeoStudio SEEP/W, slope/w, and analyzes the stability. The stability factor was evaluated utilizing fully coupled flow deformation analysis compared with the various controlling parameters such as cohesion and angle of internal friction. For slope stability analysis, slopes were modeled with only one type of soil called the homogeneous fill. The influence of each parameter on slope instability was analyzed, and the results are discussed in this paper. It was also studied whether the relationship between the slope’s instability and the controlling parameter existed. The research output shows that all chosen parameters’ value negatively affects slope stability if their variations were favorable.KeywordsSlope stabilityLandslide warningFinite element analysis
... The concept implies that a slope will fail when the driving force (gravity, applied loads or external pressures) exceeds the resisting force (soil shear strength). When the driving forces equal the resisting forces, the equilibrium condition is attained, and any further rise in driving forces results in slope failure [15][16][17][18]. Various LEM approaches presented by Duncan [19] include Fellenius method, 1927 [20], Modified Bishop Method, 1955 [21], Janbu Simplified Method, 1968 [22], Morgenstern-Price method, 1965 [23] and Spencer method, 1967 [24]. ...
Landslides present a complex challenge within the field of soil geotechnics, particularly in the context of partially saturated soil. Throughout the entire range of saturation, the soil encounters both negative and positive pore water pressure. Understanding the transition from negative to positive pore water pressure is necessary as it significantly impacts the strength of the soil. However, the determination of suction during shear tests presents difficulties, limiting the utilization of unsaturated shear strength. To address these challenges, this study conducted a comprehensive investigation into the problem of saturated–unsaturated landslide failure. The research primarily focused on examining the influence of water saturation on soil strength and stability, with a specific emphasis on the role of suction and pore water pressure. The findings show the significant contribution of suction in imparting strength to the soil within its saturation range. Notably, a direct correlation between water saturation and unsaturated shear strength was not observed due to the distinct relationships between suction, pore water pressure, and saturation. The shear parameters were found to decrease with increasing saturation. Additionally, a transition in the failure mode of the soil was observed, shifting from brittle plastic to plastic failure. Furthermore, the investigation of landslide stability under different saturation levels highlighted the importance of soil suction and pore water pressure. The comprehensive investigation of the study provides valuable insights into the relationship between water saturation and soil behavior with reference to land slope failure.
The municipal and hazardous landfills nearing its design capacity need to be isolated from the atmosphere using multi-layered cover system (MLCS). These MLCS constitutes different layers of soil and geosynthetics with widely varying properties. Each of these layers fulfil specific requirements by acting as a surface protection, drainage, separation, filtration and hydraulic barrier layers of MLCS. Failure of these MLCS leads to waste–atmosphere interaction and results in extremely hazardous situation to biosphere. The stability of MLCS significantly depends on the shear strength characteristics of materials used viz., the internal frictional characteristics of individual soil materials and interface frictional characteristics of soil–soil or soil–geotextile combination. In view of this, frictional characteristics of four type of soils, four soil–geotextile interfaces and one soil–soil interface was determined using direct shear and modified direct shear testing methods. The modification of geomembrane used in barrier layer was also attempted, for improving its interface shear characteristics. The usefulness of the above parameters and the influence of its variability on the slope stability of MLCS of a near surface low level radio-active waste disposal facility (NSDF) is demonstrated in this study.
A massive landslide wiped out the village of Malin located at 110 km from Pune city, in the Western Ghats on July
30. Mound of mud and debris that came down from a nearby hillock, swallowed up almost the entire tribal village of
around 50 families. Due to the remoteness of the village, the tragedy came to light only when the driver of the first
state transport bus reached the village a little after 7.30 am to find it uprooted. Final death toll was 153 when the
rescue operation was stopped and around 100 people were missing. This tragedy has brought the focus back on the
management –or mismanagement – of the vulnerable hills of India especially Western Ghats, Himalayas and North
Eastern states
There are many speculations about what caused such massive landslide. In this paper we are analyzing geotechnical
aspects of the catastrophe. Some of the key facts to note are, heavy rainfall before the landslide (10.8 cm on July 29)
and heavy downpour throughout the following day. This calamite is a lesson for sustainable geotechnical planning in
future to avoid massive loss of human life and property.
Detailed analysis of geotechnical facts is carried out and an attempt is made to pinpoint the cause and preventive
measures are suggested.
This paper presents field investigations and numerical analyses of the landslide, affecting Malin village of Pune district in Maharashtra, India. The Malin village was wiped out due to Malin landslide, occurred on July 30, 2014; however, only a primary school and few houses remained safe during the event, and mass of the people buried in debris of slide. To study the causes of the event, field study has been carried out. Representative samples of slope-forming geomaterials (soil/rock) have been collected at three locations of the hill viz. L1 (bottom of the hill), L2 (middle of the hill) and L3 (top of the hill) along with massive and vesicular basalt for the determination of the geotechnical properties in the laboratory. The estimated geotechnical properties have been used for numerical modeling of the hill slope that has been performed to calculate factor of safety, maximum displacement, displacement direction and accumulated maximum shear strain with the help of numerical programs based on limit equilibrium method and finite element method approaches, respectively. This study shows that the hill slope was unstable with FoS < 1 and prone to failure. It was triggered by various man-made and natural factors like heavy rainfall, unscientific construction activities at the top of the hill and along the hill, unplanned cultivations and lack of drainage system. Also, the results of the numerical analysis can be successfully implemented to minimize/reduce impact and frequency of landslide in the area of similar morphology.
A devastating landslide occurred on 30th July 2014, resulting in the burial of a village of about 40 houses called Malin, in western India and also led to about 160 deaths. The landslide was triggered by heavy rainfall in the area and mass movement of debris. The paper investigates slope failure in the Malin area using back analysis and numerical methods. Site investigation was conducted to obtain representative information of the area. Finite difference analyses using FLAC 2D is performed for the failed slope to determine the possible cause of failure. Analysis results show that slope failure occurred due to the loss of suction strength at the interface between rock and local soil.
Landslides are a significant hazard in many parts of the world and exhibit a high, and often underestimated, damage potential. Deploying landslide early warning systems is one risk management strategy that, amongst others, can be used to protect local communities. In geotechnical applications, slope stability models play an important role in predicting slope behaviour as a result of external influences; however, they are only rarely incorporated into landslide early warning systems. In this study, the physically based slope stability model CHASM (Combined Hydrology and Stability Model) was initially applied to a reactivated landslide in the Swabian Alb to assess stability conditions and was subsequently integrated into a prototype of a semi-automated landslide early warning system. The results of the CHASM application demonstrate that for several potential shear surfaces the Factor of Safety is relatively low, and subsequent rainfall events could cause instability. To integrate and automate CHASM within an early warning system, international geospatial standards were employed to ensure the interoperability of system components and the transferability of the implemented system as a whole. The CHASM algorithm is automatically run as a web processing service, utilising fixed, predetermined input data, and variable input data including hydrological monitoring data and quantitative rainfall forecasts. Once pre-defined modelling or monitoring thresholds are exceeded, a web notification service distributes SMS and email messages to relevant experts, who then determine whether to issue an early warning to local and regional stakeholders, as well as providing appropriate action advice. This study successfully demonstrated the potential of this new approach to landslide early warning. To move from demonstration to active issuance of early warnings demands the future acquisition of high-quality data on mechanical properties and distributed pore water pressure regimes.
The soil-water characteristic curve can be used to estimate various parameters used to describe unsaturated soil behaviour. A general equation for the soil-water characteristic curve is proposed. A nonlinear, least-squares computer program is used to determine the best-fit parameters for experimental data presented in the literature. The equation is based on the assumption that the shape of the soil-water characteristic curve is dependent upon the pore-size distribution of the soil (i.e., the desaturation is a function of the pore-size distribution). The equation has the form of an integrated frequency distribution curve. The equation provides a good fit for sand, silt, and clay soils over the entire suction range from 0 to 10(6) kPa.
Rainfall-induced slope failure is a common geotechnical problem in the tropics where residual soils are abundant. Although the significance of rainwater infiltration in causing landslides is widely recognized, there have been different conclusions as to the relative roles of antecedent rainfall to landslides. The relative importance of soil properties, rainfall intensity, initial water table location and slope geometry in inducing instability of a homogenous soil slope under different rainfall was investigated through a series of parametric studies. Soil properties and rainfall intensity were found to be the primary factors controlling the instability of slopes due to rainfall, while the initial water table location and slope geometry only played a secondary role. The results from the parametric studies also indicated that for a given rainfall duration, there was a threshold rainfall intensity which would produce the global minimum factor of safety. Attempts have also been made to relate the findings from this study to those observed in the field by other researchers. Results of this parametric study clearly indicated that the significance of antecedent rainfall depends on soil permeability.
As a result of population pressures, hillsides in the world's urban areas are being developed at an accelerating rate. This development increases the risk for urban landslides triggered by rainfall or earthquake activity. To counter this risk, four approaches have been employed by landslide managers and urban planners: (1) restricting development in landslide-prone areas; (2) implementing and enforcing excavation, grading, and construction codes; (3) protecting existing developments by physical mitigation measures and (4) developing and installing monitoring and warning systems. Where they have been utilized, these approaches generally have been effective in reducing the risk due to landslide hazards. In addition to these practices, landslide insurance holds promise as a mitigative measure by reducing the financial impact of landslides on individual property owners. Until recently, however, such insurance has not been widely available and, where it is available, it is so expensive that it has been little used.
Strength and deformation behavior of jointed rock is essential in the viewpoint of design of slopes, construction of tunneling and mining projects due to the presence of natural hair cracks, fissures, bedding planes, faults, etc. In order to avoid problems like loss of strength due to cracks during construction, strength and deformation characteristics of various rock matrices is helpful to simulate such cracks and to give a reliable solution. For this purpose, experimental based study was conducted on laterite rock procured from Kutch, Gujarat to evaluate the shear parameters of the proposed rock mass matrix having two horizontal cuts (at H/4 and H/2 height of the specimen) with 0°, 10° and 30° inclination with horizontal. Stress-strain characteristics and strength behavior was studied using Mohr-Coulomb strength theory and results were compared with intact rock and various jointed rock matrix specimens. Results derived from Mohr-Coulomb strength theory were also compared with the Hoek-Brown strength theory. Results demonstrated that the orientation of the rock matrix shows little increase in cohesion value and decrease in angle of internal friction with increasing inclination of cut from zero to 30° with respect to horizontal. Failure pattern was observed in jointed rock matrix specimens comprises of axial failure, block rotation, splitting of blocks through joints and shear failure.
A case study is presented in order to identify the effect of antecedent rainfall on slope stability for Singapore. A storm in February 1995 (during which 95 mm of rain fell in 2
\frac12\frac{1}{2}
h) caused more than twenty shallow landslides on the Nanyang Technological University Campus. Details of the location, size and morphology of the landslides are presented. The antecedent rainfall during the five days preceding the event was significant in causing these landslides since other rainfall events of similar magnitude (but with less antecedent rainfall) did not cause landslides. To further understand the effect of antecedent rainfall, numerical modelling of one of the slope failures is presented. The changes in pore-water pressure due to different rainfall patterns were simulated and these were used to calculate the changes in factor of safety of the slope. The results demonstrate that antecedent rainfall does play an important role in slope stability.
Annual losses in the United States, Japan, Italy, and India have been estimated at 1 billion or more each. During the period 1971-74, nearly 600 people per year were killed by landslides worldwide; about 90 percent of these deaths occurred in the Circum-Pacific region. From 1967-82, 150 people per year died in Japan as a result of slope failures. In the United States, the number of landslide-related fatalities per year exceeds 25. Japan leads other nations in development of comprehensive programs to reduce economic losses and fatalities due to landslides. The United States recently has proposed a national landslide hazard reduction program.
Stability modeling with SLOPE/W an engineering methodology Google Scholar
- J Krahn
Forensic analysis of Malin landslide in India
- P Ering
- R Kulkarni
- Y Kolekar
- Murty Dasaka
- Sivakuma Babu