Study on the damage evolution of red-bed soft rock in foundation pits under the coupled influence of drying-wetting cycles and cyclic disturbance

Abstract

Taking argillaceous sandstone collected from foundation pits as the research object, laboratory tests including drying-wetting cycles, uniaxial compression, cyclic disturbance, and acoustic emission (AE) monitoring were conducted to investigate the deterioration and fatigue damage evolution laws. The results show that, under the influence of drying–wetting cycles, the compressive strength and elastic modulus of argillaceous sandstone both decline following a power-function attenuation trend, while the ultimate fatigue strain under cyclic disturbance rises, and the spatial distribution of AE events grows more scattered. In contrast, a higher upper-limit stress ratio yields a lower ultimate fatigue strain and induces more significant spatial clustering of AE events along the shear failure plane. After being subjected to drying-wetting cycles, the fatigue failure threshold of argillaceous sandstone remains stable within the range of 75%–80% σ . Fatigue life presents a log-linear correlation with the upper-limit stress ratio, and varies in accordance with a power function against the number of drying-wetting cycles. On this basis, a three-dimensional quantitative model was established to characterize the fatigue damage evolution of argillaceous sandstone. The research findings can provide a scientific basis for the design, construction, and stability control of foundation pits in red-bed soft rock.