Shear Strength Recovery of Clayey Soils Following Discontinuation of Shear at a Residual State

Abstract

Residual shear strength is generally used for design and repairs on slopes containing pre-existing shear surfaces in large-scale landslides. Some recent research works suggest that the pre-existing shear surface of a large-scale landslide can regain strength with the passage of time, which should be considered in designing the slope stability measures. In this study, three landslide soils were tested in a ring shear apparatus with rest periods between shear of 1, 3, 7, 15, and 30 days, with the following main objectives (1) to understand the strength recovery behavior of landslide soils in residual state of shear after as long as 30 days of rest between shearing, (2) to understand the comparative pattern of strength recovery in highly plastic and less plastic soils, and (3) to understand the mechanism involved in strength recovery at residual state of shear. The obtained experimental results indicate that the recovery of shear strength in the residual state started to appear slightly after shear was discontinued for 3 days, and was lost immediately after a very small shear displacement. On the other hand, as understood from the experimental work in this study, the trend of strength recovery, is somewhat in increasing order with prolongation of the period that shear is discontinued.