Rate effects on residual strength of clays

This paper summarizes the outcome of a series of residual strength tests carried out on a clay-shale at different displacement rates. The tested high plastic clay-shale shows relatively low residual friction angle under normal laboratory test rates. There is an increase of 3.4 - 3.5% of the residual shear strength when the displacement rate is increased by ten times. The existing literature on rate effects is reviewed. Judging from the existing literature, a broad correlation between plasticity of day and rate effects is obtained. Rate effects show a nearly linear increase with the plasticity of clay.