Slope Stability Factor Research Articles

The study on length and diameter ratio of nail as preliminary design for slope stabilization

Soil nailing technology has been widely applied in practice for reinforced slope. The number of studies for the effective design of nail-reinforced slopes has also increased. However, most of the previous study was focused on a safety factor of the slope; the ratio of length and diameter itself has likely never been studied before. The aim of this study is to relate the length and diameter ratio of the nail with the safety factor of the 20 m height of sand slope in the various angle of friction and steepness of the slope. Simplified Bishop method was utilized to analyze the safety factor of the slope. This study is using data simulation to calculate the safety factor of the slope with soil nailing reinforcement. The results indicate that safety factor of slope stability increases with the increase of length and diameter ratio of the nail. At any angle of friction and steepness of the slope, certain effective length and diameter ratio was obtain. These results may be considered as a preliminary design for slope stabilization.

Sensitivity analysis of the influencing factors of slope stability based on LS-SVM

This study proposes a sensitivity analysis method for slope stability based on the least squares support vector machine (LS-SVM) to examine the influencing factors of slope stability. The method uses LS-SVM as an algorithm for machine learning. An appropriate training dataset is established according to the slope characteristics, and a testing dataset is designed orthogonally. Results of the testing data in the experiment design are calculated after training using the LS-SVM model. The sensitivity of the slope stability of each factor is examined via gray correlation analysis. The results are consistent with those of the traditional Bishop analysis and can be used as a reference for optimizing slope design.

A proposed cell model for multiple-occurrence regional landslide events: Implications for landslide susceptibility mapping

Multiple-occurrence regional landslide events (MORLEs) consist of hundreds to thousands of shallow landslides occurring more or less simultaneously within defined areas, ranging from tens to thousands of square kilometres. While MORLEs can be triggered by rainstorms and earthquakes, this paper is confined to those landslide events triggered by rainstorms. Globally, MORLEs occur in a range of geological settings in areas of moderate to steep slopes subject to intense rainstorms. Individual landslides in rainstorm-triggered events are dominantly small, shallow debris and earth flows, and debris and earth slides involving regolith or weathered bedrock.The model used to characterise these events assumes that energy distribution within the event area is represented on the land surface by a cell structure; with maximum energy expenditure within an identifiable core and rapid dissipation concentrically away from the centre. The version of the model presented here has been developed for rainfall-triggered landslide events. It proposes that rainfall intensity can be used to determine different critical landslide response zones within the cell (referred to as core, middle, and periphery zones). These zones are most readily distinguished by two conditions: the proportion of the slope that fails and the particular type of the slope stability factor that assumes dominance in determining specific sites of landslide occurrence. The latter condition means that the power of any slope stability factor to distinguish between stable and unstable sites varies throughout the affected area in accordance with the landslide response zones within the cell; certain factors critical for determining the location of landslide sites in one part of the event area have little influence in other parts of the event area. The implication is that landslide susceptibility maps (and subsequently derived mitigation measures) based on conventional slope stability factors may have only limited validity for many events.The overall ability to predict the impact of these events and consequently the development of effective mitigation measures is limited by the ability to predict the travel path, storm centre, and intensity range within the cell structure of extreme weather systems.

Stability of intact slopes with tensile strength cut-off

The Mohr–Coulomb yield criterion, typically used in slope stability analyses, predicts the uniaxial as well as the isotropic (triaxial) tensile strength. In this study, the tensile strength was reduced or eliminated from the yield condition in order to determine whether it has any consequences on the outcome of the stability analyses of slopes. It was discovered that the consequences on the slope stability factor are very significant. Slopes that are most affected by the tension cut-off are steep slopes, particularly in the presence of seepage. The difference in stability factor for steep slopes calculated with the classical Mohr–Coulomb strength envelope and a criterion with tensile strength cut-off can exceed 50% for steep slopes subjected to seepage (70% for vertical slopes). Tension cut-off used in the analysis permits deformation modes with the dilatancy angle exceeding the internal friction angle, and this is the likely cause of producing more critical mechanisms of slope collapse. The novelty of this study is in presenting a new slope stability analysis that accounts for tension cut-off, and in demonstrating the significant impact of reduced tensile strength on the outcome of the stability assessment.

Linkages between precipitation cycle and slope stability: A case study in the Caijiapo landslide among Weihe River Basin

It is of great importance to forecast landslide in future certain time interval. Hence, this study proposed a method combination precipitation period with variety of slope stability factor based on macro scale. This study designed 5 grades of rainfall strength simulation and corresponding 5 grades of slope state using Markoff prediction technique analysis change of slope factor K in the short time. Results indicated that: (1) the rainfall in Baoji area has three periods of 5a, 13a and 25a, in which 5a is the primary period; (2) the slope safety factor K has a similar fluctuation trend compared to precipitation state, thus division slope factor K of 5 grade as safety state, basically safety state, stable state, partial risk state and risk state, respectively; (3) in the previous year if slope in the safety, basically safe and stable state, in the next year slope factor K above 1.15 has 60%, 75% and 72% probability, respectively; (4) when the previous year at partial risk or risk situation, there is high probability that value of the K is always more than 1.15, it is means to a great extent the landslide have already occurred, thus defined a concept which between “the safety state after destruction” and “safety state have no destruction”.

Numerical analysis of evaluation methods and influencing factors for dynamic stability of bedding rock slope

As the inclination of a bedding surface is consistent with the inclination of a slope, the stability of a bedding rock slope is relatively poor, especially under dynamic loads such as earthquake and blasting. In the dynamic stability analysis of slope, the evaluation methods and influence factors of slope stability are two important concerns. Therefore, two typical bedding rock slopes are respectively established by FLAC3D to study the above concerns. The pseudo-static method, dynamic time-history method and dynamic strength reduction method is used to evaluate the dynamic stability of the model slope, and the applicability of the three methods is compared. The influence of five parameters including dynamic load frequency, slope angle, slope height, strata inclination and strata thickness on the dynamic stability is considered in the model slope with a set of bedding planes. The results show that the dynamic strength reduction method has good suitability for the stability evaluation of a bedding rock slope due to its good solution in the instability judgment and evaluation index. The dynamic stability of a slope becomes worse when the load frequency is close to the natural frequency of the slope. Due to the “elevation effect” and “bedding surface effect” in the dynamic slope response, the slope stability decreases with the increase of slope height and the reduction of strata thickness. The slope stability decreases with the increase of strata inclination and slope angle, and the strata inclination is the most sensitive parameter influencing the slope stability. When the slope angle and height increase to a certain value, the downward trend of slope stability gradually become gentle. For the model slope in this paper, when the slope angle reaches 55° and the slope height reaches 200 m, the reduction of slope stability will be no longer obvious with the increase of a slope angle and slope height.

Comparative Slope Stability Analysis and Factor of Safety Evaluation of Gambhar Landslide

Comparative Slope Stability Analysis and Factor of Safety Evaluation of Gambhar Landslide

3D stability analysis method of concave slope based on the Bishop method

In order to study the stability control mechanism of a concave slope with circular landslide, and remove the influence of differences in shape on slope stability, the limit analysis method of a simplified Bishop method was employed. The sliding body was divided into strips in a three-dimensional model, and the lateral earth pressure was put into mechanical analysis and the three-dimensional stability analysis methods applicable for circular sliding in concave slope were deduced. Based on geometric structure and the geological parameters of a concave slope, the influence rule of curvature radius and the top and bottom arch height on the concave slope stability were analyzed. The results show that the stability coefficient decreases after growth, first in the transition stage of slope shape from flat to concave, and it has been confirmed that there is a best size to make the slope stability factor reach a maximum. By contrast with average slope, the stability of a concave slope features a smaller range of ascension with slope height increase, which indicates that the enhancing effect of a concave slope is apparent only with lower slope heights.

Análisis cuantitativo en la influencia de la geomorfología en la estabilidad de taludes

Landslide occurrence is associated with some conditioning factors and triggering landslide processes. This research contributes to quantify the influence of geomorphology as a conditioning factor in slope stability, via analysis based on a finite element method with an elastoplastic constitutive model. The analysis performs through a numerical simulation with nine three-dimensional slope models. The spatial variation of the stress tensor and its components were obtained by the invariants that reflect the influence of the geoform and flow regime in slope stability. Finally, the authors calculated an index potential failure that quantifies, in a unified manner, the influence of the confinement pressure and shear stress in the slope to determine a susceptibilty failure area.

Field monitoring of groundwater responses to heavy rainfalls and the early warning of the Kualiangzi landslide in Sichuan Basin, southwestern China

The Kualiangzi landslide was triggered by heavy rainfalls in the “red beds” area of Sichuan Basin in southwestern China. Differing from other bedrock landslides, the movement of the Kualiangzi landslide was controlled by the subvertical cracks and a subhorizontal bedding plane (dip angle < 10°). The ingress of rainwater in the cracks formed a unique groundwater environment in the slope. Field measurement for rainfall, groundwater movement, and slope displacement has been made for the Kualiangzi landslide since 2013. The field monitoring system consists of two rainfall gauges, seven piezometers, five water-level gauges, and two GPS data loggers. The equipments are embedded near a longitudinal section of the landslide, where severe deformation has been observed in the past 3 years. The groundwater responses to four heavy rainfall events were analyzed between June 16 and July 24 in 2013 coincided with the flood season in Sichuan. Results showed that both of the water level and the pore-water pressure increased after each rainfall event with delay in the response time with respect to the precipitation. The maximum time lag reached 35 h occurred in a heavy rainfall event with cumulative precipitation of 127 mm; such lag effect was significantly weakened in the subsequent heavy rainfall events. In each presented rainfall event, longer infiltration period in the bedrock in the upper slope increased the response time of groundwater, compared to that of in the gravels in the lower slope. A translational landslide conceptual model was built for the Kualiangzi landslide, and the time lag was attributed to the gradual formation of the uplift pressure on the slip surface and the softening of soils at the slip surface. Another important observation is the effect on the slope movement which was caused by the water level (H w) in the transverse tension trough developed at the rear edge of the landslide. Significant negative correlation was found for H w and the slope stability factor (F s), in particular for the last two heavy rainfall events, of which the drastic increase of water level caused significant deterioration in the slope stability. The rapid drop (Δ = 22.5 kPa) of pore-water pressure in the deep bedrock within 1 h and the large increase (Δ = 87.3 mm) of surficial displacement were both monitored in the same period. In the end, a four-level early warning system is established through utilizing H w and the displacement rate D r as the warning indicators. When the large deformation occurred in flood season, the habitants at the leading edge of the landslide can be evacuated in time.

Slope Stability Analysis Under Combined Failure Criteria

Strength reduction finite element method (SRFEM) has been widely used to analyze the slope stability. Strength Reduction Factor (SRF) is yielded as the slope Factor Of Safety (FOS) when a running-though shear failure zone comes into being, in which the Plastic Element EQuivalent strain (PEEQ) is employed as the judgment of shear failure initiation in this paper. Moreover, the filed variable is set as same as SRF along the solution processing, FOS can be directly determined as the cor-responding value of field variable when the shear failure zone goes through. Three typical slopes with varying foot gradients of 26.6, 45 and 78.7 in degree are analyzed and fantastic results have been yielded, well agreeing with the Spencer’s results, when the linear Mohr-coulomb failure criterion is employed. However, during the solution process, tensile failure zone initiates at the slope top while the plastic failure zone initiates at the slope toe and this indicates that the failure mode of slope is combined. The results show that the combined failure zone with plastic failure and tensile failure appears much earlier than the unique plastic failure zone, which indicates that the traditional analytic method and SRFEM based on the unique linear Mohr-coulomb plasticity criteria overestimated the slope stability factor.

Uncertainty analysis of safety factor of embankment built on stone column improved soft soil using fuzzy logic α-cut technique

Uncertainty in safety factor (FS) of slope stability is a main subject in geotechnical engineering. Uncertainties are associated with shear strength parameters of the soil, their complex nature, numerical analysis methods, etc. The main aim of this research was to improve the model used by other researchers for determination of FS of embankments built on stone column improved soft soils, and compare the results with what was found in literature using α-cut fuzzy technique (FAC). The results showed that the highest and lowest uncertainty occurred at equivalent area with existence of underground water, and for single stone column with no underground water respectively. A reduction factor proposed to amend the FS calculated using the equivalent area method. In the equivalent area model, the equivalent parameters were used. This contribution might have real and more precise behavior in comparison with what was suggested by other researchers in literature. In addition, with applying of membership functions, the height of embankment had the most effect on the values of FS obtained using finite element (FE) and finite difference (FD) methods.

Identification of flash flood hazard zones in mountainous small watershed of Aceh Besar Regency, Aceh Province, Indonesia

Flash-floods develop at space and time scales that conventional observation systems were not able to monitor for rainfall, stream flow and sediment discharge. This condition resulted in greater casualties and tremendous economic losses. One of the regions in Indonesia affected by the flash floods was Aceh Besar Regency. It was located in Krueng Teungku watershed. The flash floods were recurring events, which occurred in 1987 and 2000. The disaster reocurred on January 2, 2013 at 19:30P.M. with the huge impact. This study aimed to analyze the factors affecting flash flood hazards and to obtain flash flood hazard zones at the Krueng Teungku watershed. The method used in this study was weighted overlay technique through Geographic Information System (GIS). The result revealed the information about the flash flood hazard zones at Krueng Teungku watershed as the model for the early warning. Through the development of this model, flood forecasting capabilities in the watershed without measuring devices can be improved. This paper provided the review of factors that affect the incidence of flash flooding, including the factors of peak discharge, slope, watershed shape, stream gradient, damming, drainage density, erosion, slope stability and reservoir volume. The information factors were expected as a contribution for research agencies and government (Aceh Disaster Management Agency) to guide the disaster risk reduction (DRR) activities of flash floods.

Influence law of multipoint vibration load on slope stability in Xiaolongtan open pit mine in Yunnan, China

The purpose of this work was to explore the influence law of vibration load on rock mass structure and slope stability. Based on the type and transmission way of vibration stress wave, the main stress in the horizontal and vertical directions was analyzed and the superposition effect of the stress wave was revealed. After the mechanical analysis of the sliding mass, the calculation formulas of the anti-sliding force and the sliding force were derived and the damage mechanism of blasting vibration to the structural plane was defined. In addition, according to the structure and lithologic parameter of the slope as well as the vibration monitoring data, the west slope stability of Xiaolongtan open pit mine was analyzed. The results show that the time-dependent stability factor is proportional to the vibration speed and the peak values appear at the same time. Vibration load promotes the breakage of the structural plane leading to the drop of the west slope stability factor by 0.23%. Under the multipoint simultaneous blasting, the fluctuating laws of the stability factors are consistent. The more the start-up points are, the higher the weakening degree to the slope stability is. Under the multipoint allochronic blasting, the stability factor depends on the synthetic waveform structure of all vibration waves. The greater the blasting time difference is, the lower the weakening degree to the slope stability is. Selecting the reasonable quantity of start-up points and time difference could fully reduce the adverse influence of vibration load to slope stability.

Slope stability analysis based on quantum-behaved particle swarm optimization and least squares support vector machine

Given the complexity and uncertainty of the influencing factors of slope stability, its accurate evaluation is difficult to accomplish using conventional approaches. This paper presents the use of a least square support vector machine (LSSVM) algorithm based on quantum-behaved particle swarm optimization (QPSO) to establish the nonlinear relationship of slope stability. In the proposed QPSO-LSSVM algorithm, QPSO is employed to optimize the important parameters of LSSVM. To identify the local and global optimum, three popular benchmark functions are utilized to test the abilities of the proposed QPSO, the nonlinearly decreasing weight PSO, and the linearly decreasing weight PSO algorithms. The proposed QPSO exhibited superior performance over the other aforementioned algorithms. Simulation results obtained from PSO-LSSVM, QPSO-LSSVM, and LSSVM algorithms are compared in a case. Case analysis shows that QPSO-LSSVM has the quickest search velocity and the best convergence performance among the three algorithms, and is therefore considered most suitable for slope stability analysis.

Effect of Extreme Rainfall on Cut Slope Stability: Case Study in Yen Bai City, Viet Nam

This paper addresses the effects of extreme rainfall on the stability of cut slopes in Yen Bai city, Northern Viet Nam. In this area, natural slopes are excavated to create places for infrastructures and buildings. Cut slopes are usually made without proper site investigations; the design is mostly based on experience. In recent years, many slope failures have occurred along these cuts especially in rainy seasons, resulting in properties damaged and loss of lives. To explain the reason that slope failure often happens during rainy seasons, this research analyzed the influence of extreme rainfalls, initial ground conditions, and soil permeability on the changes of pore water pressure within the typical slope, thereafter determining the impact of these changes on the slope stability factor of safety. The extreme rainfalls were selected based on all of the rainfalls triggering landslide events that have occurred over the period from 1960 to 2009. The factor of safety (FS) was calculated using Bishop's simplified method. The results show that when the maximum infiltration capacity of the slope top soil is less than the rainfall intensity, slope failures may occur 14 hours after the rain starts. And when this happens, the rainfall duration is the deciding factor that affects the slope FS values. In short, cut slopes in Yen Bai may be stable in normal conditions after the excavation, but under the influence of tropical rain storms, their stability is always questionable.

Research on Security Risk Assessment System of Soil Slope Based on AHP

Based on the investigation of soil slope in Zhejiang province, the main influence factors of soil slope stability were analyzed and the risk assessment indexes of soil slop were selected. Then the risk assessment model of soil slope was established by the method of analytic hierarchy process according to the importance of each index. The security risk assessment system of soil slope was obtained finally. The research result has important reference for the soil slope management.

Post-earthquake rainfall-triggered slope stability analysis in the Lushan area

The “4.20” Lushan earthquake in Sichuan province, China has induced a large amount of geological hazards and produced abundant loose materials which are prone to post-earthquake rainfall-triggered landslides. A detailed landslide inventory was acquired through post-earthquake emergent field investigation and high resolution remote sensing interpretation. The rainfall analysis was conducted using historical rainfall records during the period from 1951 to 2010. Results indicate that the average annual rainfall distribution is heterogeneous and the largest average annual rainfall occurs in Yucheng district. The Stability Index MAPping (SINMAP) model was adopted to assess and analyze the post-earthquake slope stability under different rainfall scenarios (light rainfall, moderate rainfall, heavy rainfall, and rainstorm). The model parameters were calibrated to reflect the significant influence of strong earthquakes on geological settings. The slope stability maps triggered by different rainfall scenarios were produced at a regional scale. The effect of different rainfall conditions on the slope stability is discussed. The expanding trend of the unstable area was quantitatively assessed with the different critical rainfall intensity. They provide a new insight into the spatial distribution and characteristics of post-earthquake rainfall-triggered landslides in the Lushan seismic area. An increase of rainfall intensity results in a significant increase of unstable area. The heterogeneous distribution of slope instability is strongly correlated with the distribution of earthquake intensity in spite of different rainfall conditions. The results suggest that the both seismic intensity and rainfall are two crucial factors for post-earthquake slope stability. This study provides important references for landslide prevention and mitigation in the Lushan area after earthquake.

边坡稳定梯度法优化计算中新的差分格式与收敛准则

用极限平衡方法计算边坡稳定的安全系数，需要采用优化方法寻找最危险滑裂面。梯度法是一种精确的优化方法方法，然而在边坡稳定分析中存在不能准确找到最危险滑裂面的问题。改进了梯度优化方法，提出了优化方向向量的下降差分格式。它解决了采用中心差分格式出现的搜索方向错误的问题，在有效性、计算精度和优化时间方面都优于中心差分格式。指出了传统梯度优化方法中忽视收敛标准的问题，并提出了一个单变量或多变量沿着优化方向进行优化搜索时的收敛准则。采用2阶段圆弧滑动面搜索方法，对3个测试算例的安全系数进行了下降差分格式和中心差分格式优化搜索的对比，表明改进的梯度法结合下降差分格式是能跳出局部极值的精确有效的方法。算例中采用下降差分格式搜索结果的误差均小于给定误差标准，表明所提出的收敛准则是合适的。 It is necessary to use optimization methods to find the most dangerous sliding surface for the safety factor of slope stability calculated by the limit equilibrium method. Gradient method is an accurate optimization method, however there may fail to find accurately the most dangerous sliding surface. An improved gradient optimization method with a descent difference scheme for the calculation of the direction vector is proposed. The descent difference scheme is superior to the central difference scheme both in accuracy and consuming time. The problem of wrong search direction occurring in the central difference scheme is dissolved in this scheme. The problem of convergence criterion used in the classical optimization method based on the gradient of the objective function is pointed out. A new convergence criterion for single variable optimization or for multivariable optimization along the gradient direction is proposed. The stability of three test examples is analyzed with a two-stage search method for circular slip surface. The gradient method combined with the descent difference scheme is an accurate and efficient method with an ability of avoiding to fall to a local minimum in a search process. The errors of search results in the test examples are less than the given convergence error. The proposed convergence criterion is appropriate.

Study on the Predominant Outward Joints Influence on the Stability of High Slope

The advantage outward joints connectivity rate (CR) which extend along the slope plays an important role to overall stability of the high rock slope, but less research on it has been done. In order to research the 180m high rock slope at water inlet of Wudongde hydropower station at Jinsha River, qualitative and quantitative analysis methods have been used. Based on the statistics of the outward joints CR which extend along the slope, and the weighted average parameters of the “bottom sliding surface” combined with the rock bridge, the stability factor of slope has been calculated by rigid body limit equilibrium method. According to the CR sensitivity analysis and calculation, the effect degrees of the joint connectivity rate to the slope stability, and the effect degrees of the bandwidth selection to the CR and stability factors in the bandwidth projection method of linear CR have been demonstrated in paper.