Numerical Investigation of Active Earth Pressure under Transient Flow condition in Unsaturated Soil Using Lower Bound Finite Element Limit Analysis

Abstract

It is very important to precisely evaluate the lateral earth pressure for the stability of geotechnical structures such as retaining walls and bridge abutments from the safety point of view. It has been studied that the existing conventional approaches mostly focus upon saturated conditions, thereby often neglecting the spatial and temporal variability that are associated with unsaturated soils. In reality, the study of time dependent (transient) changes in flow and matric suction, influenced by infiltration, urges the scientists to adopt both steady and time-dependent states in their analysis. The present study aims to evaluate the lateral active earth pressure (AEP) on a retaining wall supported by unsaturated soils under transient flow, by incorporating lower-bound finite element limit analysis (FELA) coupled with second-order conic programming (SOCP) for optimization purpose. The results highlight the effects of wall height, infiltration time, angle of internal friction, and wall and backfill inclinations on the variation of active earth pressure coefficient . Results show that fine-grained soils show more variations in active earth pressure under the transient state than coarse-grained soils. Further, the results of the present study have been validated with existing literature, in order to improve the understanding the behavior of unsaturated soil, especially focussing on the effects of transient flow on foundation performance.