Analytical Three-Dimensional Mechanism for Stability of Slurry Trenches in Cohesive Soils

Abstract

This paper presents an analytical three-dimensional rotational mechanism for the limit analysis on the overall stability of slurry trenches in layered cohesive soils. The proposed mechanism differs from the traditional torus mechanism in terms of the assumption on the shapes of cross section. The proposed rotational mechanism can have cross section with arbitrary shapes that are described by a smooth rotation radius function. The factor of safety for the overall stability of slurry trenches is obtained by using the new kinematic mechanism. The performance of the proposed mechanism is evaluated by analyzing the overall stability of trenches in single-layered, uniform and nonuniform clayey soils. The computed results are compared with the solutions given by finite-element limit analysis (FELA), which show that the proposed mechanism can give better solutions than the traditional torus mechanism when the length-to-depth ratio of the trench is relatively small. Based on the proposed mechanism, the stability of slurry trenches in layered undrained clay is investigated. The results show that, for trenches in two-layered undrained clay, the strength ratio between the shallow and deep layers can significantly influence the depth of the collapse mechanism. For trenches in three-layered undrained clay with a weak interlayer, the thickness of the interlayer can greatly affect the modes of failure in terms of global or local instability.