Influence of dilatancy on slip planes and on localization of strains

Abstract

Correct calculation of slip plane geometry plays a key role in the design of geotechnical structures. The goal of this study is the identi cation of slip planes in cohesionless soils retained behind walls and quantifying the failure plane geometries to measurable and calculable soil properties. For this purpose, 1 g small scale re- taining wall model tests were performed. Soil mass behind the model retaining wall was prepared at different relative densities corresponding to different dilation angles ( p) to monitor both the effect of dilative behavior on slip plane geometry and strain distribution within the failure wedge. Model test results were analyzed using particle image velocimetry (PIV) for the detection and identi cation of shear planes associated with retaining wall failure. The results show that generated failure surfaces at active and passive failure states behind horizontally translating rigid walls are not planar. This is an expected outcome which is attributed to the dilatant nature of the back ll. However, as a novel approach, this study attempts to quantify the geometry of failure planes as functions of dilatancy angle. Thus, an empirical equation that uses dila- tancy angle as input is proposed to predict the failure surface geometry of cohesionless back lls behind retaining walls at active state. It is observed that the geometries of slip planes calculated using the proposed empirical equation are in good agreement with the results from the experimental models. Addittionally, shear band formation within the active failure wedge is investigated using an image processing technique in MATLAB program, which allows the examination of the distribution of shear strains along the shear bands. Accordingly, it is noted that dilatant behavior in uences both thickness and inclination of shear bands.