Seismic Slope Stability Analysis Research Articles

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.

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”

Discussion of “Probabilistic seismic slope stability analysis and design”

Discussion of “Probabilistic seismic slope stability analysis and design”

Discussion of “Probabilistic seismic slope stability analysis and design”

Discussion of “Probabilistic seismic slope stability analysis and design”

Finite-element upper-bound analysis of seismic slope stability considering pseudo-dynamic approach

The present study presents a novel procedure to assess the seismic slope stability, using the finite-element upper-bound method combined with the pseudo-dynamic approach. A pioneering work is performed to incorporate the pseudo-dynamic accelerations into the finite-element upper-bound analysis which combines the advantages of upper bound and finite element methods. The finite element method is principally used to discretize the domain of soil mass into finite elements, aiming to construct a kinematically admissible failure mechanism based on which the external and internal rates of work can be expressed. Based on the upper bound theorem, the upper bound formulations are derived from the virtual work rate equation, in the form of slope safety factor and limit surcharge acting on the slope crest. The problem of seeking the optimal upper bound solution is transformed to solve a linear programming problem within numerous kinematically admissible velocity fields, and this is achieved by using the interior-point algorithm implemented into the MATLAB. Pseudo-dynamic solutions are calculated and compared with the pseudo-static, limit equilibrium and FLAC results. The proposed procedure is versatile in considering the homogeneity and non-homogeneity of soil strength properties in seismic slope stability analysis. A benchmark problem with 0.5 m thick weak interlayer is discussed.

Seismic fragility functions for slope stability analysis with multiple vulnerability states

The seismic performance and stability analysis of slopes are important in predicating damage and mitigating potential losses in landslide-prone areas. Fragility functions can give results of slope performance assessment that are more comprehensive and richer. This study presents a procedure of constructing seismic fragility functions for slope stability analysis with various vulnerability states based on incremental dynamic analysis (IDA). IDA is a performance-based earthquake engineering analysis based on a series of dynamic time history analyses conducted for suitable multiple-scaled seismic records. IDA not only estimates the seismic demand and capacity of systems but also provides basic data for the estimation of fragility functions. Firstly, an ensemble of seismic records meeting the requirements of specific site conditions of a slope is selected to consider the randomness of ground motion. A series of seismic stability analyses of the slope are performed to obtain the dynamic safety factor time history of the slope. Each minimum safety factor and corresponding seismic intensity measure is then extracted to develop a set of IDA curves. On the basis of IDA results, analytical seismic fragility functions of a slope are developed considering the prescribed various vulnerability states of the slope in terms of the safety factor. The failure probabilities of exceeding different specific vulnerability states for a given intensity measure of the earthquake are finally obtained.

Probabilistic seismic slope stability analysis and design

Deterministic seismic slope stability design charts for cohesive–frictional ([Formula: see text]) soils are traditionally used by geotechnical engineers to include the effects of earthquakes on slopes. These charts identify the critical seismic load event that is sufficient to bring the slope to a state of limit equilibrium, but they do not specify the probability of this event. In this paper, the probabilistic seismic stability of slopes, modeled using a two-dimensional spatially random [Formula: see text] soil, is examined for the first time using the random finite element method (RFEM). Slope stability design aids for seismic loading, which consider spatial variability of the soil, are provided to allow informed geotechnical seismic design decisions in the face of geotechnical uncertainties. The paper also provides estimates of the probability of slope failure without requiring computer simulations. How the design aids may be used is demonstrated with an example of slope remediation cost analysis and risk-based design.

Economical Design of Reinforced Slope Using Geosynthetics

Slope failures triggered by earthquakes are one of the most important geotechnical earthquake hazards that can cause severe damage to road/rail embankments, bridge abutments and dams. In the present paper, a road embankment of height 5 m is designed for Roorkee region using locally available soil as per the Indian Standards Specifications. Seismic slope stability analysis is also carried out to ensure the safety of the constructed or designed embankment under seismic loading appropriate to the considered region. The factor of safety obtained is unsatisfactory and hence there was need of reinforcement. Geosynthetics used for reinforcement include geotextiles and geogrids. Geosynthetics aims to ensure strength, stability and serviceability over its intented life span. To assess slope stability of reinforced slope, a single soil slope was analysed using Geostudio 2004 to estimate factor of safety under static and dynamic conditions. This study proposes a geotechnical stable slope embankment and also, the economical design using geosynthetics in both static and dynamic loading conditions which can be of great help in practical applications of geotechnical earthquake engineering.

Discussion of “New Perspective on Seismic Slope Stability Analysis” by Changbing Qin and Siau Chen Chian

Discussion of “New Perspective on Seismic Slope Stability Analysis” by Changbing Qin and Siau Chen Chian

Implementation of a large deformation finite element modelling technique for seismic slope stability analyses

Post-slide investigations show large displacement of failed soil mass in many earthquake-triggered landslides. An Eulerian-based finite-element modelling (FEM) of large deformation of soil, for pseudostatic and dynamic loadings, is presented in this study. The Eulerian FEM is compared with Lagrangian-based explicit and implicit finite-element (FE) modelling approaches. The dynamic FE modelling of two hypothetical slopes for eight earthquake acceleration–time histories show that the failure surfaces develop progressively, which cannot be modelled using the traditional limit equilibrium method (LEM). A large plastic shear strain concentration (i.e. shear band formation) occurs when the strain-softening behaviour of soil is considered. The similarities and differences between the results of dynamic and pseudostatic FE analyses based on estimated pseudostatic coefficient from acceleration–time records are presented. The duration of an earthquake influences the failure process and displacement of the failed soil mass. The displacement of the toe obtained from FEM is compared with Newmark's simplified approach. The developed Eulerian-based FE modelling technique has been used to simulate large-scale landslides in sensitive clays due to earthquake loading [1].

Impact of Earthquake Characteristics on Seismic Slope Stability Using Modified Pseudodynamic Method

Seismic slope stability analysis is often limited by the ability to encompass specific earthquake characteristics, such as shaking amplitude, frequency, and time as well as varying soil properties, such as cohesion and friction angle across the depth with consideration of damping and amplification. In this paper, a simple procedure that combines the discretization-based kinematic analysis and modified pseudodynamic method is presented to offer a more holistic analysis considering earthquake and soil characteristics more appropriately. This is achieved by the implementation of the discretization-based kinematic analysis along with a modified pseudodynamic method. The discretization technique aids to generate a kinematically admissible failure surface with considerations to varied soil strength parameters. Its significance lies in the preprocessing to generate a unique failure mechanism dependent on the varied soil properties of the slope while also facilitating the work rate calculations. The use of the modified pseudodynamic method is adopted in this study to overcome the shortcomings of the pseudostatic and simple pseudodynamic method, enabling one to consider the complete time history of earthquake-induced ground movement, having also considered the amplification effect when shaking approaches the soil’s natural frequency. Equating the external and internal rates of work by integration of elementary rates yields the closed-form solution in yield seismic acceleration and/or slope-bearing capacity. A parametric study with a range of independent variables, accompanied with detailed discussion, is also presented to offer a more pragmatic perspective on the performance of nonuniform stratified slopes subjected to earthquakes.

Adjustment of spectral pseudo-static approach to account for soil plasticity and zone seismicity

The concept of the spectral pseudo-static procedure has been developed at the Université de Sherbrooke as an alternative to the conventional pseudo-static approach for the seismic stability analysis of clayey slopes. The destabilizing effect of an earthquake is approximated, in the new approach, by an inertial force that hyperbolically varies with depth while being proportional to the maximum acceleration of the seismic event. Its results have been rigorously verified against available static and dynamic laboratory tests, and have been extensively validated by a series of simulations performed using the computer code FLAC. Good agreements have been achieved between the results of the spectral pseudo-static procedure and complete numerical analyses, in terms of the computed safety factors and the critical slip surfaces. This implies that the spectral pseudo-static approach can be integrated into available limit equilibrium (LE) software providing a useful tool to examine the effect of dynamic soil characteristics on the proposed seismic coefficient profiles. The herein-reported study extends the previous endeavors to examine and quantify the effect of plasticity index (PI) (0%, 15%, 30%, 50%, and 100%) on the proposed formula of seismic coefficient profile using the same numerical modelling and assumptions. Original analyses were carried out considering earthquakes compatible with the seismicity of Quebec City (zone 4), and they have been repeated in the current study for earthquakes compatible with other regions having different seismicity (zones 2, 3, and 5). Based on the results of the current analyses, side-formulas were established between the spectral pseudo-static coefficient on ground surface for any value of soil plasticity index (PI) and the corresponding coefficient originally used in the main formula (PI = 30%).

Behaviour of a loose silty sand under static and cyclic loading conditions

In recent years, considerable progress have been made in the study of liquefaction and flow failures with the introduction of the notion of steady-state of deformation and “collapse” envelope. These concepts are increasingly used in seismic stability analysis of slopes or embankments. However, as most of these studies were carried out on clean sands in the triaxial apparatus, one may question the general applicability of these results to practical conditions as several factors such as anisotropy, fines content, undrained strength anisotropy, boundary deformation conditions, stress history, etc. may play an important role. In this paper, the behaviour of the same soil, a loose silty sand, is compared for different loading and testing conditions: drained and undrained triaxial compression tests, drained and constant volume monotonic and cyclic direct simple shear (DSS) tests. Results allow to identify similarities and differences, in terms of undrained initial and steady-state shear strength and modes of undrained failure between triaxial and DSS test conditions and show that liquefaction in DSS cyclic tests is an instability triggered by shear failure developing once the friction corresponding to the characteristic envelope, as identified in the monotonic test, has been mobilized.

Seismic stability analysis of slopes with pre-existing slip surfaces

In analyzing seismic stability of a slope with upper bound limit analysis method, the slip surface is often assumed as a log-spiral or plane slip surface. However, due to the presence of a weak layer and unfavorable geological structural surface or a bedrock interface with overlying soft strata, the preexisting slip surface of the slope may be irregular and composed of a series of planes rather than strictly log-spiral or plane shape. A computational model is developed for analyzing the seismic stability of slopes with pre-existing slip surfaces. This model is based on the upper bound limit analysis method and can consider the effect of anchor bolts. The soil or rock is deemed to follow the Mohr-Coulomb yield criterion. The slope is divided into multiple block elements along the slip surface. According to the displacement compatibility and the associated flow rule, a kinematic velocity field of the slope can be obtained computationally. The proposed model allows not only calculation of the rate of external work owing to the combined effect of self-weight and seismic loading, but also that of the energy dissipation rate caused by the slip surface, interfaces of block elements and anchorage effect of the anchors. Considering a direct relationship between the rate of external work and the energy dissipation rate, the expressions of yield acceleration and permanent displacement of anchored slopes can be derived. Finally, the validity of this proposed model is illustrated by analysis on three typical slopes. The results showed that the proposed model is more easily formulated and does not need to solve complex equations or time consuming iterations compared with previous methods based on the conditions of force equilibrium.

Seismic stability analysis of rock slopes by yield design theory using the generalized Hoek-Brown criterion

The stability of rock slope is studied using the kinematic approach of yield design theory, under the condition of plane strain and by considering the last version of the Hoek-Brown failure criterion. This criterion, which is suitable to intact rock or rock mass highly fractured regarded as isotropic and homogeneous, is widely accepted by the rock mechanics community and has been applied in numerous projects around the world. The failure mechanism used to implement the kinematic approach is a log-spiral rotational mechanism. The stability analysis is carried out under the effects of gravity forces and a surcharge applied along the upper plateau of the slope. To take account of the effects of forces developed in the rock mass during the passage of a seismic wave, the conventional pseudo-static method is adopted. This method is often used in slope stability study for its simplicity and efficiency to simulate the seismic forces. The results found are compared with published numerical solutions obtained from other approaches. The comparison showed that the results are almost equal. The maximum error found is less than 1%, indicating that this approach is effective for analyzing the stability of rock slopes. The relevance of the approach demonstrated, investigations are undertaken to study the influence of some parameters on the stability of the slope. These parameters relate to the mechanical strength of the rock, slope geometry and loading.

Seismic stability analysis of rock slopes by yield design theory using the generalized Hoek-Brown criterion

The stability of rock slope is studied using the kinematic approach of yield design theory, under the condition of plane strain and by considering the last version of the Hoek-Brown failure criterion. This criterion, which is suitable to intact rock or rock mass highly fractured regarded as isotropic and homogeneous, is widely accepted by the rock mechanics community and has been applied in numerous projects around the world. The failure mechanism used to implement the kinematic approach is a log-spiral rotational mechanism. The stability analysis is carried out under the effects of gravity forces and a surcharge applied along the upper plateau of the slope. To take account of the effects of forces developed in the rock mass during the passage of a seismic wave, the conventional pseudo-static method is adopted. This method is often used in slope stability study for its simplicity and efficiency to simulate the seismic forces. The results found are compared with published numerical solutions obtained from other approaches. The comparison showed that the results are almost equal. The maximum error found is less than 1%, indicating that this approach is effective for analyzing the stability of rock slopes. The relevance of the approach demonstrated, investigations are undertaken to study the influence of some parameters on the stability of the slope. These parameters relate to the mechanical strength of the rock, slope geometry and loading.

Quantifying exposure of linear infrastructures to earthquake-triggered transverse landslides in permafrost thawing slopes

Seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. In addition, rapid ice melting in low-permeability fine-grained soils can lead to excess pore-water pressure build-up and cause instability in slopes even at small angles. This study addresses the active-layer detachment (ALD) slope instability hazard and develops a systematic risk assessment framework for existing and future linear infrastructures, such as energy pipelines, bridges, and roads traversing permafrost regions. Mild slopes, with average gradient of 7°, are considered in this study as the most representative of actual field conditions. The potential for earthquake-triggered ALD is analytically quantified. State-of-the-art ALD morphological statistics for northern Canada are combined with seismic slope stability analyses to determine (i) the probability of linear infrastructure exposure to permanent ground deformations (PGDs) caused by ALD and (ii) the extent of the potential PGD that the linear infrastructure may be subjected to. The Monte Carlo technique is applied to simulate and assess the sensitivity of the model to parameters such as earthquake magnitude and source-to-site distance. Findings from this study can be used to evaluate the vulnerability of linear infrastructures exposed to the ALD hazard.

Time-frequency analysis of instantaneous seismic safety of bedding rock slopes

An earthquake wave has many non-linear and non-stationary components. In current methods for seismic slope stability analysis, the time-frequency-amplitude characteristics of the earthquake waves, which can significantly affect the computation results, are not taken into account. In this paper, formulas for computing the seismic safety factor of bedding rock slopes are derived based on the elastic wave mechanics. The Hilbert-Huang transform (HHT) signal processing technique is employed to identify the time-frequency-amplitude characteristics of the earthquake waves in the time-frequency domain. Then a time-frequency method for computing the instantaneous seismic safety factor of bedding rock slopes, which considers the time-frequency-amplitude characteristics of the earthquake waves simultaneously, is proposed. A shaking table test example is worked out to illustrate the application of the proposed time-frequency analysis method to a bedding rock slope. The instantaneous seismic safety factors of all bedding planes are calculated based on the time-frequency analysis method proposed in this research. The seismic safety factor changes significantly over time, and the seismic safety factor of the upper part of the bedding rock slope is smaller than that of the lower part of the bedding rock slope. Hence the upper part of the bedding rock slope is more vulnerable to seismic damage.