A coupled strain softening and hardening model for completely weathered granite in a fault zone

Abstract

This study focused on exploring the specificity of mechanical behavior for completely weathered granite, as a special soil, by consolidated drained triaxial tests. The influences of dry density (1.60, 1.70, 1.80 and 1.90 g/cm³), confining pressure (100, 200, 400 and 600 kPa), and moisture content (13.0%, that is, natural moisture content) were investigated in the present work. A newly developed Duncan-Chang model was established based on the experimental data and Duncan-Chang model. The influence of each parameter on the type of the proposed model curve was also evaluated. The experimental results revealed that with varying dry density and confining pressure, the deviatoric stress–strain curves have diversified characteristics including strain-softening, strain-stabilization and strain-hardening. Under high confining pressure condition, specimens with different densities all showed strain-hardening characteristic. Whereas at the low confining pressure levels, specimens with higher densities gradually transform into softening characteristics. Except for individual compression shear failure, the deformation modes of the specimens all showed swelling deformation, and all the damaged specimens maintained good integrity. Through comparing the experiment results, the strain-softening or strain-hardening behavior of CWG specimens could be predicted following the proposed model with high accuracy. Additionally, the proposed model can accurately characterize the key mechanical indicators, such as tangent modulus, peak value and residual strength, which is simple to implement and depends on fewer parameters.

Keywords

completely weathered granite / mechanical behavior / consolidated drained triaxial test / constitutive model