Seismic Slope Stability Research Articles

Under and post-construction probabilistic static and seismic slope stability analysis of Barmshour Landfill, Shiraz City, Iran

Under and post-construction probabilistic static and seismic slope stability analysis of Barmshour Landfill, Shiraz City, Iran

Seismic stability analysis of slopes with cracks in unsaturated soils using pseudo-dynamic approach

In practice, soil slopes are commonly unsaturated and may suffer from the adverse effects of earthquakes. Stability assessment of slopes subjected to earthquakes tends to consider whether the soils are dry or saturated while neglecting the time and spatial effects of seismic waves; in such assessments, the actual features cannot be reflected sufficiently. In the present study, a framework considering unsaturated soils was developed to investigate the seismic stability of slopes accounting for tension cracks using the pseudo-dynamic approach. Several expressions for apparent cohesion were applied to analyze the influence of matric suction, and seepage under different phreatic levels was also included. The pseudo-dynamic approach was applied to characterize the time and spatial effects of earthquakes. Two types of cracks, open cracks (cracks existing prior to slope failure) and formation cracks (cracks forming as part of a slope failure mechanism), were considered. A closed-form solution for the critical height of the slopes was derived from the energy balance equation of the Limit Analysis upper bound method, and the safety factor was obtained. The validity of this approach was verified by comparison with published solutions. Through the parametric analysis, it was found that higher amplification factors and seismic coefficients led to a smaller discrepancy in the safety factor between the slopes with open cracks and formation cracks, yet a reverse trend was observed at a higher value of matric suction. The effect of matric suction on slope stability was more apparent with a lower water level. Different shear strength models of unsaturated soils led to different safety factors.

Parametric study of structural parameters affecting seismic stability in slopes reinforced by pile-anchor structures

Parametric study was performed on the seismic stability of pile-anchor slope reinforcement structures for earth retaining wall with different structural parameters. Dynamic finite element analysis and the Newmark permanent displacement method were combined to derive the dynamic time-history response of the pile-anchor structure and evaluate slope seismic stability. The effects of pile embedment, pile thickness, anchor position on the pile, anchor free length, anchor direction and anchor prestress were investigated by batch calculation under different structural conditions, and optimized design suggestions are proposed based on the numerical study. The quantitative analysis indicates that Newmark permanent displacement can effectively evaluate slope stability under seismic loading and provide an accessible approach to improve the performance-based design of pile-anchor structures. For the generalized vertical soil slope prevalent in actual slope engineering, considering the maximum factor of safety and minimum permanent displacement, it was found that the most optimized embedded depth occupies approximately 30% of the whole pile length in the soil slope, and the pile thickness is set as 1.5–2 m for superior shear and bending strength. In addition, there is a critical anchor position 3 m beneath the pile top, a threshold free length of the anchor cable of 9.5 m, as well as an optimal direction within the range of 15°–20°. Furthermore, the pile-anchor structure shows better sliding resistance with rational anchor prestress accounting for 20% of the sliding force. The slope seismic stability evaluation based on dynamic finite element analysis with different pile-anchor structural parameter conditions performed in this paper may lay a foundation for the design optimization of pile-anchor reinforcement structures for better dynamic performance.

A generalized seismic sliding model of slopes with multiple slip surfaces

AbstractEarthquake‐induced permanent displacements of slopes are generally evaluated through the simplified sliding block analyses of a singular coherent mass on a predefined failure plane. However, coseismic landslides may exhibit multiple slip surfaces as a result of earthquake shaking. This study presents a generalized seismic sliding analysis using a column of sliding blocks to model seismic slope failures with multiple slip surfaces. The formulation of the sliding mode equations of the block system is obtained by a rigorous theoretical derivation. Both a rigid soil column associated with an acceleration–time series that is constant with depth, and a flexible soil column considering an acceleration–time series that varies throughout the sliding mass is presented. The conditional yield accelerations and the equivalent seismic accelerations are defined to characterize the complex interplay of the sliding block assemblies. The approach is applied to model the seismic sliding behavior of layered slopes in which failures would likely occur at the interfaces between soil layers with different shear strengths. The effects of input ground motions and soil deposits on the sliding patterns of slopes are investigated. The developed generalized model provides a promising means for evaluating the seismic slope stability by combining a number of seismic failure locations within slopes.

Reliability Analysis of Seismic Slope Stability with Uncertain Probability Distributions

Abstract The probability density function or cumulative distribution function of shear strength parameters is commonly unknown, and the first-order reliability method, second-order reliability meth...

Modeling of rapid evaluation for seismic stability of soil slope by finite element limit analysis

The rapid evaluation of post-earthquake landslides and unstable slopes (whether they will be revived by aftershocks) is a key task in the post-earthquake emergency response phase. Stability chart and Newmark model is generally used for rapid evaluation of seismic stability of soil slopes. In this study, a novel method for directly estimating static, pseudo-static safety factors and critical accelerations of soil slopes is proposed; this method overcomes the limitations of stability chart and Newmark model. Based on finite element limit analysis and Mohr-Coulomb criterion, safety factors and critical acceleration of typical slope models are studied via the parametric method. First, a stability chart of safety factors under static and pseudo-static states is calculated by finite element limit analysis. Correspondingly, the critical acceleration under static condition is obtained. Next, the seismic weighting factor and slope angle weighting factor are put forward, and a rapid evaluation model of safety factors is established. Finally, according to the correlation between safety factors and critical acceleration under static conditions, a rapid evaluation model for critical acceleration is proposed. The proposed method is compared with the results of the Newmark model and finite element limit analysis. The results show that the prediction accuracy of the proposed method is closer to the results of finite element limit analysis than those of Newmark model. The proposed seismic stability model is reliable and efficient and can be used to evaluate the stability of soil slope at the initial design stage and provide reference for further seismic design.

A simplified nonlinear coupled Newmark displacement model with degrading yield acceleration for seismic slope stability analysis

AbstractThe use of Newmark permanent displacement to preliminarily evaluate the seismic performance of earth slopes has been well accepted in geotechnical community. Essentially, the seismic displacement would cause slope soil shear strength to reduce, thus causing the slope yield acceleration to degrade during the earthquake shaking. This phenomenon is known as degrading effect of yield acceleration, which has not been fully addressed in the literature. In this study, the degrading effect is investigated on the basis of various Newmark's displacement calculation frameworks for infinite slopes. Specifically, the flexible‐deformation‐recoverable soil columns as well as the nonlinear soil dynamic properties including the damping and shear modulus are taken into account to derive the coupled Newmark model. Detailed discussions are made to the possible influence of the degrading effect of yield acceleration in different schemes of Newmark displacement calculation frameworks. The parametric studies show that the seismic displacement calculated by the proposed method reaches peak value at small period ratio, and dramatically drops to zero when the period ratio increases. Furthermore, the possible influence of shear rate on soil shear strength is also discussed.

Dynamic response of rock slope with anti-dip weak interlayer and its influencing factors under seismic actions

The load features of ground motion are mainly reflected by three factors: amplitude, frequency, and duration. The combination of these factors determines the response of rock-soil mass and the structure safety under seismic load. By finite element method, this paper analyzes the influence of the three factors of ground motion on the dynamic response of a slope. The analysis shows that the slope displacement increased with the elevation from the bottom. The anti-dip fault puts the slope in an unfavorable deformation state. Due to the large residual deformation in the fault zone, a large displacement occurred on the slope top. It was also learned that the adjustment of amplitude only leads to proportional growth in the absolute value of the acceleration of the slope. Under the same conditions, the dynamic responses in different parts of the target slope are not greatly affected by the changing amplitude, but depend more on the material and spectral features of the rock-soil mass. The research results provide a reference for the evaluation and prediction of slope seismic stability and the evolution of slope damage under earthquakes with different frequencies, amplitudes, and durations.

Determination of Critical Slope Face in c – ϕ Soil under Seismic Condition Using Method of Stress Characteristics

This study proposes a plasticity-based approach to ensure the static and seismic stability of a finite soil slope supporting a uniformly distributed surcharge on the horizontal top surface. Most of the available investigations based on the limit equilibrium and the limit analysis method mainly rely on the assumed slip surface to determine the stability of a slope with a given geometry. The present analysis employs the method of stress characteristics coupled with the original pseudodynamic approach to trace the actual slip surface of a soil slope under the seismic condition. The results are presented in terms of the critical slope face (CSF) corresponding to a global factor of safety of 1.0. The obtained CSF can be used as a reference to determine the stability of slopes with different geometries. The current approach supersedes the available theories developed to analyze slopes by presenting a more general solution without assuming any predefined slip surface. The proposed idea is endorsed with a detailed parametric study that demonstrates the influence of various parameters such as cohesion and the angle of internal friction of soil, surcharge loading, and seismic wave properties on the stability of a finite slope. As a notable outcome, this investigation promotes a bilinear or concave slope face, which may be an efficient and economical alternative to the traditional linear slope face.

Seismic internal stability of bilinear geosynthetic-reinforced slopes with cohesive backfills

The bilinear geosynthetic-reinforced slope (BGRS) is a new two-tier reinforced earth structure without an offset. Analyzing its seismic internal stability is aimed to determine the resultant reinforcement force. In this paper, using a top-down log spiral mechanism, the moment limit equilibrium equations are established to formulate the resultant reinforcement forces for upper and lower tiers of the BGRS, considering influence of angle of lower tier, depth of tension crack, cohesion of backfill and pseudo-static seismic loads. Results show that ignoring cohesion of backfill and/or vertical upward seismic load is beneficial to conservative stability analysis, and the existence of tension cracks changes the distribution of reinforcement forces in upper and lower tiers. Additionally, the critical slip surface is also studied, which is found that the volume of the failure body decreases under the global stability with increase of angle of lower tier, cohesion of backfill or depth of tension crack, or with the decrease of seismic coefficients.

Probabilistic evaluation of the seismic stability of infinite submarine slopes integrating the enhanced Newmark method and random field

For evaluation of the seismic stability of submarine slopes, traditional deterministic methods may not reflect the actual situation due to the uncertainties in input values such as seismic acceleration, soil properties, and hydraulic conditions. In this study, probabilistic analyses were conducted based on the use of an enhanced Newmark method to evaluate the seismic stability of submarine slopes. In the probabilistic workflow, the infinite slope model was used, whereby the spatially varied strengths of marine sediments were simulated by non-stationary random fields discretized by the Karhunen-Loeve expansion. The positions of the potential slip surfaces were searched automatically, rather than being predefined as in the traditional limit equilibrium method. Artificial earthquake accelerations, exhibiting the same spectral characteristics, were simulated as the input ground motions in the probabilistic analysis. The pore water pressure generation and dissipation models were incorporated into the enhanced Newmark method when calculating the permanent displacements of the submarine slopes. Monte Carlo simulations were conducted for statistical characterization of the slope displacements and their failure probabilities. The results of the analysis indicate the superiority of the probabilistic framework and demonstrate the significant effects of pore water pressure and the spatial variability of the soil strength on the displacements and failure probabilities of submarine slopes.

Failure Mechanism of Rock Slopes under Different Seismic Excitation

In earthquake‐prone areas, special attention should be paid to the study of the seismic stability of rock slope. Particularly, it becomes much more complicated for the rock slopes with weak structural surfaces. In this study, numerical simulation and the shaking table test are carried out to analyze the influence of seismic excitation and structural surface in different directions on dynamic response of rock slope. Huaping slope with bedding structural surfaces and Lijiang slope with discontinuous structural surfaces besides Jinsha River in Yunnan Province are taken as research objects. The results of numerical simulation and the model test both show that discontinuous structure surface has influence on the propagation characteristics of seismic wavefield. For Huaping slope, the seismic wavefield responses repeatedly between the bedding structural surface and slope surface lead to the increase of the amplification effect. The maximum value of seismic acceleration appears on the empty surface where terrain changes. Horizontal motion plays a leading role in slope failure, and the amplification coefficient of horizontal seismic acceleration is about twice that of vertical seismic acceleration. The failure mode is integral sliding along the bedding structural surface. For Lijiang slope, seismic acceleration field affected by complex structural surface is superimposed repeatedly in local area. The maximum value of seismic acceleration appears in the local area near slope surface. And the dynamic response of slope is controlled by vertical and horizontal motion together. Under the seismic excitation with an intense of 0.336 g in X direction and Z direction, the amplification coefficients of seismic acceleration of Lijiang slope are 3.23 and 3.18, respectively. The vertical motion leads to the cracking of the weak structural surface. Then, Lijiang slope shows the toppling failure mode under the action of horizontal motion.

Seismic stability analysis for a two-stage slope

This paper adopts the kinematic theorem of limit analysis to assess the seismic stability of a two-stage slope. The seismic effect is taken into account by using the pseudo-static approach. The failure mechanism for the slope is extended to include below-toe failure, toe failure and face failure. Validation of this approach is conducted by comparing the factor of safety with the data in the existing literatures. The stability charts are presented based on the graphical method for reading the factor of safety readily. Parametric study involving the effect of slope geometry, internal friction angle, seismic effect as well as depth coefficient on the stability of a two-stage slope is carried out. The critical failure surfaces with various parameters are plotted. The results obtained reveal the significant influence of slope geometry on the failure mechanism of a two-stage slope under static and seismic condition.

Seismic stability of three-dimensional slopes considering the nonlinearity of soils

Slopes are often unstable in adverse natural conditions, especially when suffering from seismic hazards. Due to the fact that conventional pseudostatic method fails to consider the dynamic properties of seismic waves, a pseudodynamic approach is adopted to characterize the seismic acceleration which varies with time and space. According to the upper bound theorem of limit analysis, an alternative strategy that slices the failure blocks in the horizontal direction to consider the spatial variations of seismic waves is proposed. Moreover, to consider the nonlinearity of the soil strength parameters, a tangential technique is used to capture the equivalent Mohr-Coulomb (M − C) parameters to obtain the least upper bound solution. The factor of safety (FOS) of the slope is implicitly restricted in the work balance equation established by the limit analysis upper-bound method with respect to a three-dimensional (3D) rotational mechanism. With the aid of the strength reduction technique, the least FOS can be eventually derived. By comparing to the pseudostatic method to the existing solutions, the validity and rationality of the proposed method is proven. A parametric study is carried out to reveal the influence of dynamic factors and nonlinear strength parameters on the safety of a slope.

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.

Seismic Slope Stability Analysis of a Hydraulic Fill Dam

Abstract This paper presents a seismic slope stability assessment study of an inherently heterogeneous hydraulic fill dam in Texas. Extensive cone penetration soundings conducted at the dam site we...

Seismic slope stability and failure process analysis using explicit finite element method

Earthquake is one of the primary factors that triggers the failure of slopes and the landslides in the mountainous area. In this study, an efficient method for the seismic slope stability analysis and seismic failure process simulation is proposed. The seismic slope stability and the failure process of a two-dimensional slope model are analyzed via the explicit finite element method with the influence of the dynamic mechanical behavior of soil and the frictional resistance characteristic of the slope rupture surface. A dynamic visco-elasto-plastic constituted model for soil is established and written in FORTRAN as a user subroutine of the finite element method code of ABAQUS. The validation of the visco-elasto-plastic constituted model and the explicit finite element method are compared with the experimental results and the implicit method. The seismic factor of safety and the sliding distance of the soil slopes under the natural earthquake conditions are calculated via the dynamic visco-elasto-plastic constituted model and the explicit finite element method. The influence of the ground motion characteristics on the seismic slope stability is analyzed in this study via the specified elastic response acceleration spectrum. The analysis results of this paper suggest that the seismic slope stability analysis and the progressive failure process of the slope under the seismic condition can be analyzed by the explicit finite element method efficiently. The results show that the dynamic mechanical behavior of soil and the ground motion characteristics are both critical influence factors for the seismic slope stability. The frictional resistance characteristic of the slope rupture surface is the principal influence factor for the sliding distance of the slope, and it also has more influence on the sliding distance of a high slope than that of the small slope.

Probabilistic investigation of the seismic displacement of earth slopes under stochastic ground motion: a rotational sliding block analysis

Earthquakes frequently induce landslides and other natural disasters that would have a huge impact on human life and properties. In geotechnical engineering, evaluation of the seismic stability of earth slopes has been attracting a substantial amount of research interest. In this regard, the Newmark permanent displacement provides a simple yet effective index of slope co-seismic performance. The traditional Newmark method involves many assumptions and the displacement results thereby calculated are subject to various degrees of uncertainty. In this paper, a modified rotational sliding block model considering depth-dependent shear strength and dynamic yield acceleration is established. The seismic critical slip surface is analysed through a pseudo-static approach, where the failure volume is larger than that in the static condition. The dynamic yield acceleration is updated by considering the instantaneous movement of the sliding mass in each time-step. The parametric sensitivity of soil shear strength, slope geometry, and Arias intensity to the seismic displacement is also analysed. Results show that the internal friction angle and the cohesion have equal effects on the permanent displacement. On a logarithmic scale, the displacement approximately linearly correlates with Arias intensity. Furthermore, the underlying uncertainty of the ground motion is introduced to obtain the probabilistic distribution of the seismic slope displacement. The uncertainty of earthquake time history details has considerable influence on the permanent displacement results. Under the specific allowable displacement, the probability of failure increases exponentially with seismic intensity.

Three-dimensional seismic stability of slopes reinforced by soil nails

Seismic stability of slopes reinforced with soil nails has been traditionally investigated by two-dimensional limit equilibrium method. In this paper, the strength reduction method in combination with the kinematic approach of limit analysis is employed to assess the factor of safety (Fos) of slopes reinforced by soil nails using the three-dimensional rotational failure mechanism. The pseudo static approach is used to represent the seismic effects. Both the tensile failure and pull-out failure of soil nails are considered in the computations of internal energy dissipations. Comparisons are made to validate the proposed approach, which shows that the implemented approach is an efficient design tool for evaluating the factor of safety of slopes reinforced by soil nails. Parametric analysis is conducted to discuss the influence of model parameters, including nail length, nail density, soil shear strength and seismic forces, on slope stability. A set of stability charts is finally provided for fast assessments of slope safety.

Reply to the discussion by Huang on “Probabilistic seismic slope stability analysis and design”

Reply to the discussion by Huang on “Probabilistic seismic slope stability analysis and design”