Kinematics of Shear Zone Deformation in Soft Sensitive Clays

Abstract

Sensitive clays, exhibits softening, are characterized by a response in which shear stress increases monotonically up to a peak value, and decreases with further increase of shear strain i.e. second order work becomes negative, during the shear deformation and will therefore develop excess pore pressure in the shear bands. Due to the low permeability of clays in combination with a generally high deformation rate, the failure process is often considered being undrained and analyzed using a total stress approach. However, if thin localized shear zones develop, local pore-water dissipation will take place. This diffusion process may be important to define the shear bands. To study this process an effective stress based soil model is needed. The model must incorporate a formulation for how excess pore pressures accompany the softening process. Keeping in view, a simple direct shear sample (DSS) test and one dimensional soil column is simulated to analyze the coupled strain softening pore water mechanism. This study is initiated to test the hypothesis that a finite shear band thickness may result for a given deformation rate.