Evaluating the active earth pressure exerted by granular soils with nonlinear strength behaviour using the slice-based limit equilibrium method

Abstract

ABSTRACT Conventional earth pressure theories are generally applicable to soils with a linear strength envelope. Preferred granular backfill, however, usually exhibits a decreasing peak friction angle with an increasing normal effective stress. In this study, the slice-based limit equilibrium method is used to evaluate the active earth pressure applied by soils that exhibit nonlinear strength behaviour. The force and moment equilibrium equations for a differential soil slice are introduced, and the boundary conditions for the active earth pressure problems are specified. The mathematical nature of the active earth pressure is explored. It is found that the active earth pressure corresponds to a stationary point on a saddle surface. Seeking the active earth pressure is equivalent to identifying the maximum from a series of local minima. By introducing a combination of two functions for the inter-slice force angle distribution, the local minimisation process for each possible failure surface is implemented by varying the combination factor within its valid range. The proposed solution strategy is compared with existing methods and reasonable agreement is obtained. The influences of the inter-slice force angle distribution on the resultant active earth pressure and its position of application are also studied by using three different combination functions.