Experimental study on shear characteristics of granite residual soil under different consolidation conditions

In order to study the triaxial undrained shear characteristics of granite residual soil under different consolidation conditions, the triaxial undrained shear tests of undisturbed granite residual soil with different consolidation stress ranges (10~50 kPa, 100~300 kPa) were carried out under isobaric and K₀ consolidation conditions, and the shear characteristics were analyzed. The results showed that: The consolidation method affected the stress-strain relationship of granite residual soil. The pore pressure value of the isobaric consolidation sample was higher than that of the K₀ consolidation sample, and the negative pore pressure appeared when the confining pressure was less than 50 kPa. The pore pressure gradually increased with the increase of the confining pressure, and the failure mode of the sample was consistent with the shear state shown by the pore pressure. When the data were fitted based on the Mohr-Coulomb strength criterion, the cohesion value of the soil obtained under high stress was larger, the internal friction angle value was smaller, and the cohesion value obtained by K₀ consolidation was higher. The generalized power function could describe the strength nonlinearity of granite residual soil. The total stress tangent friction angle of the K₀ consolidated sample was higher than that of the isobaric consolidated sample, and the effective stress tangent friction angle obtained by the K₀ consolidation was larger at low stress. The consolidation method had a great influence on the deformation characteristics of granite residual soil. It was easy to overestimate the ultimate strain and affect the safety of the project by using the isobaric consolidation method.