The evolution of cracks in red clay under wet and dry cycles and its influence on shear strength

Abstract

Using computer image processing technology and lots of triaxial experiments, the fracture evolution rules and shear strength indexes of red clay in the wet and dry cycles were analyzed, and the functional relationship between shear strength indexes of red clay and fracture density was established. The parameters in slope stability calculation were also discussed by the strength indexes reduction method. The results show that with the increase of the times of dry and wet cycles, the crack density gradually increases and eventually it remains stable. During the first two wet and dry cycles, the crack development of red clay was the most obvious. After the dry-wet cycle, the stress-strain curve of the red clay is weakly hardened and the failure mode is bulging. The shear strength of red clay is significantly reduced by the influence of dry wet cycle. After the first cycle, the attenuation of strength indexes is obvious, and the final strength indexes trend to be stable. The attenuation amplitude of the cohesive force is significantly larger than the internal friction angle. After the wet-dry cycle, the stable value of its cohesion becomes 54% ∼ 57% of the initial value, and the stable value of the internal friction angle becomes 45% ∼ 63% of the initial value, so it is recommended to use the value of the long-term strength index and it is more accurate to calculate the slope stability under dry and wet cycles. Under the action of dry and wet cycles, a quadratic polynomial can be used to fit the functional connection between the crack density of red clay and the index of shear strength.