3D Limit Analysis of the Transient Stability of Slope during Pile Driving in Nonhomogeneous and Anisotropic Soil

Zhihao Mo,Jian Wu,Pingping Rao

doi:10.1155/2020/7560219

Abstract

To evaluate the stability of a slope subjected to pile driving in nonhomogeneous and anisotropic soils, an upper-bound limit analysis method is employed in this paper. A 3D rotational failure mechanism for soil slope is extended to account for different failure patterns (i.e., toe failure and base failure). In order to avoid missing the global minimum, an efficient optimization method is simultaneously employed to find the least upper bound to the factor of safety (FS). The effectiveness and accuracy of the proposed method is well demonstrated by comparing the results obtained from the proposed approach with the solutions from published literatures. The effects of key designing parameters are presented and discussed. The optimal pile location and the three-dimensional effect of the slope are discussed. In addition, these results highlight that the adverse effects of pile driving on slope stability should be highly concerned during the design of geotechnical infrastructures, rather than emphasizing the reinforcement effect of a pile only.

Highlights

In geotechnical engineering, the stabilization of slopes by placing piles has been one of the most innovative and effective reinforcement techniques in recent years
Current approaches for analyzing the stability of 3D slopes can be mainly divided into three categories: (1) traditional limit-equilibrium method, (2) numerical approaches, and (3) limit analysis. e most commonly used limit-equilibrium approach for 3D slope stability analysis is usually a direct extension from various 2D slice methods
Due to the simplicity and efficiency, the limit analysis method (LAM) used in the 3D slope stability analysis has received increasing attention over recent decades [11,12,13,14]. e advantages of LAM mainly include that (i) it does not require any assumption of stresses on the failure surfaces and the critical failure surface can be determined automatically; (ii) this method only involves one unknown parameter (i.e., factor of safety (FS))

Summary

Introduction

The stabilization of slopes by placing piles has been one of the most innovative and effective reinforcement techniques in recent years. Conte et al [16] adopted appropriate constitutive models that account for the nonlinearity of piles and soil to analyze the response of reinforced concrete flexible piles subjected to inclined loads based on the 3D finite element approach These analyses are limited to homogeneous and isotropic soils, while soils are heterogeneous and anisotropic in nature. Based on Advances in Civil Engineering the kinematic approach of limit analysis, the upper-bound expression for the FS is defined as the ratio of the internal energy dissipation rate to the external work rate. Based on the upper-bound limit analysis, equating the work rate of critical external forces Wcr to the rate of internal energy dissipation D and combining with equation (2) leads to the expression of the FS as. By employing the upper-bound limit analysis and force-increase technique, the FS is defined as the ratio of the internal energy dissipation rate to the external work rate. Following the procedure similar to Michalowski and Drescher [1] and Chen [22], the expressions of W and D for the 3D base-failure mechanism are derived as follows:

Plane insert

DC z

Dc Wc