Seismic stability and displacement analyses of earth slopes using non-circular slip surface

The seismic stability and deformability of earth slopes are conventionally evaluated by simple, practical methods. Because a multimodal function optimization problem makes it mathematically difficult to search large critical slip surface of earth slopes with complex strata, stability analysis is one of the classical problems of geotechnical engineering. One option is to evaluate the seismic deformability of earth slopes using permanent seismic displacements via Newmark's sliding block analysis in the current seismic design. The advantage of this method is that it is useful in practice and is less time consuming in terms of calculations. However, the calculations require that the critical slip is assumed either linear or circular. This paper proposes two methods for computing safety factors and permanent seismic displacements of earth slopes using an efficient non-circular slip surface search algorithm based on the force equilibrium given by the Spencer method. The validity of these proposed methods is verified by applying them to models with a known safety factor or theoretically calculated permanent seismic displacement and the results obtained compared. Comparative analyses are also conducted in order to demonstrate their efficacy in terms of computation precision and convergence performance. Further, they are utilized to calculate the pertnanent seismic displacement of a practical earth slope model subjected to seismic motions in both the horizontal and vertical directions. The results obtained indicate that they can calculate the safety factor of earth slopes using a smaller number of simulations than conventional methods and that they can also be applied to calculate the pertnanent seismic displacement of earth slopes. The results also indicate that the permanent seismic displacement calculated is an important index that can be used to quantitatively evaluate the seismic performance of earth slopes. (C) 2015 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.