Crack Evolution and Strength Attenuation of Red Clay under Dry–Wet Cycles

Abstract

Red clay is a special soil that loses water and shrinks easily, which causes expansion and contraction and leads to the generation and development of cracks, weakening the strength and engineering properties of the soil. This investigation analyzed the mechanism of crack evolution and patterns of strength decay in red clay under dry–wet cycles and established a relationship between strength and crack ratio by employing image processing techniques and conducting direct shear tests on red clay with various initial moisture contents and humidification times. The results show that the crack ratio increases with the number of dry–wet cycles and eventually tends to be stable after the fourth dry–wet cycle, and the stress–displacement curve of red clay changes from weak hardening to hardening. With the progress of the dry and wet cycles, the shear strength indexes of red clay decrease extensively, displaying a negative association with the sample’s initial moisture content and the duration of humidification. Based on the experimental result, a quadratic function was established to model the relationship between soil cracking ratio and shear strength, which can predict the shear strength of red clay from the cracking ratio.