Seismic Slope Stability Analysis Research Articles

Seismic stability analysis of fractured rock slopes by yield design theory

This paper deals with the problem of stability of fractured rock slope located in seismic area. The rock mass is crossed by two sets of fractures which are considered to be planar, parallel and persistent. The effects of both horizontal seismic coefficient and strength characteristics of fractures are addressed. The analysis is based upon the kinematic approach of the yield design theory and the pseudo-static method as well. The fundamental inequality of the kinematic approach is invoked and the failure of the fractured rock slope is considered through simple translational mechanism involving a one-partsliding block. Rigorous upper bounds of the so-called stability factor for the structure under study of given slope angle, strength properties of constituent materials and seismic loads are obtained. The results are presented in the form of stability charts relating the estimated upper bound solutions to the friction angle of fractures. The used procedure highlights the destabilizing effects of the seismic loadings and is capable of conducting parametric studies. Furthermore, the results obtained far from various sets of data show good performance and further research work is planed to extend the analysis to include a large number of sub-problems.

せん断強度低減法による斜面の静的・動的安定解析

せん断強度低減法による斜面の静的・動的安定解析

Geotechnical characteristics and slope stability in the Gulf of Cadiz

Sedimentological and geotechnical analyses of thirty-seven core samples from the Gulf of Cadiz continental margin were used to define the regional variability of sediment properties and to assess slope stability. Considering the sediment property data set as a whole, there is an association between grain size, plasticity and water content. Any one of these properties can be mapped regionally to provide an indication of the dominant surface sediment lithology. Based on static sediment strength, a simplified slope stability analysis showed that only steep slopes (>16° for even the most vulnerable sediment) can fail under static loading conditions. Accordingly, transient loads, such as earthquakes or storms, are needed to cause failure on more moderate slopes. A regional seismic slope stability analysis of the Cadiz margin was performed based on detailed geotechnical testing of four gravity core samples. The results showed that the stability of these slopes under seismic loading conditions depends upon sediment density, the cyclic loading shear strength, the slope steepness, and the regional seismicity. Sediment density and cyclic loading shear strength are dependent upon water content, which can act as a proxy for plasticity and texture effects. Specifically, sediment in the water content range of 50–56% is most vulnerable to failure under cyclic loading within the Cadiz margin. As a result, for a uniform seismicity over the region, susceptibility to failure during seismic loading conditions increases with increasing slope steepness and is higher if the sediment water content is in the 50–56% range than if it is not. The only sampled zone of failure on the continental slope contains sediment with water content in this critical range. Storm-wave-induced instability was evaluated for the continental shelf. The evaluation showed that a storm having hundreds of waves with a height in the range of 16 m might be capable of causing failure on the shelf. However, no sediment failures were observed on the shelf that might have been caused by this mechanism.

Seismic Performance of Simple Slopes

ABSTRACT This paper is concerned with an extension of a rotational limit equilibrium method for determining the permanent displacements of slopes under seismic excitation. In the proposed procedure, the sliding mass is treated as a rigid rotating body defined by a log spiral trace. Permanent displacements are obtained by double-integration of the equation of motion in a manner similar to Newmark’s translational sliding block method. The seismic slope stability analysis is based on the rotational (variational) limit equilibrium approach. This stability analysis was verified with dynamic experimental results obtained from centrifuge model testing. A series of parametric studies was conducted on “unstable” slopes, investigating the effects of soil properties and characteristics of excitation on the magnitude of permanent displacements. The higher the frictional angle, the smaller the permanent displacement of the slope is. Low excitation frequency yields larger slope displacement if the excitation is extended for the same time period of time. The effect of frequency becomes less distinct when a larger value of yield seismic coefficient is used. The proposed procedures produce a rational criterion to evaluate the seismic performance of simple slopes. This criterion is based on permanent displacement limit rather than factor of safety alone.

Seismic Slope Stability Analysis: Pseudo-Static Generalized Method

ABSTRACT This paper extends a generalized slope stability analysis method to include pseudo-static forces. Formulation and the subsequent numerical procedure of the extended generalized seismic slope stability analysis are presented. Comparison with a closed form approach indicates that the generalized method yields the same safety factor as the closed form approach. This can serve as a partial verification of the accuracy of the numerical procedures. Comparison with other rigorous limit equilibrium methods of seismic slope stability demonstrates that the presented method yields the smallest factor of safety.

Evaluation of soil properties for seismic stability analysis of slopes : Martin, G R Proc Conference Stability and Performance of Slopes and Embankment II, Berkeley, 29 June–1 July 1992V1, P116–142. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31)

Evaluation of soil properties for seismic stability analysis of slopes : Martin, G R Proc Conference Stability and Performance of Slopes and Embankment II, Berkeley, 29 June–1 July 1992V1, P116–142. Publ New York: ASCE, 1992 (ASCE Special Geotechnical Publication No 31)

Nonlinear Dynamic Slope Stability Analysis

A procedure is described for performing nonlinear dynamic slope stability analysis. The method combines updated Lagrangian kinematic relations with a cap‐type, strain‐hardening soil plasticity model in an explicit nonlinear dynamic finite element formulation. A detailed analysis of the progressive failure of an embankment is performed and comparisons with conventional methods for seismic slope stability analysis are presented. The results presented indicated the applicability and accuracy of the proposed method.

Seismic Displacements in Slopes by Limit Analysis

TO avoid the complication in the calculation of progressive failure using the stress‐strain approach, and the inaccuracy of using the pseudo‐static analysis in seismic slope stability analysis, it is desirable to develop an effective method with which the critical state of the slope and the effects of earthquake on the slope stability can be determined directly. The present work is an attempt, within the framework of conventional pseudo‐static analysis, to develop a model for the evaluation of the critical state and the subsequent displacement response of slopes to earthquakes. The upper‐bound pseudo‐static limit analysis is applied for the determination of critical state of slopes, in this case, the yield acceleration and corresponding failure mechanism. Based on the calculated yield acceleration and the critical failure surface, Newmark's analytical procedure is then used to assess the soil displacements of slopes, which are subjected to a given earthquake load.