Stress-Strain Behavior and Strength Criterion of Frozen Silty Clay under Varying Intermediate Principal Stresses

Abstract

The impact of intermediate principal stress on the shear strength of frozen soil is rarely addressed. This study presents plane-strain test results of frozen silty clay at relatively high confining pressure using a custom-made true triaxial apparatus and analyzes the impact of intermediate principal stress and minor principal stress on its strength properties. Further, a p-q strength criterion accounting for the effects of intermediate principal stress was proposed. The experimental results revealed that as intermediate principal stress and minor principal stress increase, the shear strength rises and then drops under plane-strain testing conditions. The relationships between the mean confining pressure, the generalized shear stress and the strain in the major principal stress direction under different minor principal stress values exhibit strain-hardening characteristics. The relationships between the generalized shear stress at failure and mean confining pressure at failure curves, the strength ratio and mean confining pressure at failure curves, as well as the strength ratio and intermediate principal stress at failure all exhibit conical shapes. The shear strength ratio declines with increasing intermediate principal stress ratio, demonstrating the negative impact of intermediate principal stress on the shear resistance of frozen silt clay. Moreover, there exists a critical intermediate principal stress ratio, beyond which the strength ratio decreases rapidly. The proposed p-q strength criterion can effectively reflect the effects of intermediate principal stress and minor principal stress as well as the mean confining pressure on the strength characteristics of frozen silty clay under plane-strain testing conditions. The experimental data and proposed model offer insight into frozen fine-grained soils at high confining pressures at complex loading conditions.