Abstract: Ring shear tests were conducted on the clayed sliding-zone soil of the Majiagou landslide to investigate the effects of water content and shear rate on its shear behavior. Furthermore, a statistical damage constitutive model was developed based on damage mechanics and statistical theory to describe strain-softening, revealing the relationship between sliding-zone soil damage evolution and reservoir-induced landslide development. The results show that the clayed sliding-zone soil exhibits distinct strain softening behavior. As water content increases, the shear strength and residual friction coefficient of the sliding-zone soil decrease. The shear rate has varying effects on the shear strength of the sliding-zone soil across different intervals. Within a shear rate range of 0.1−1.0 mm/min, shear strength shows minimal variation. However, when the shear rate exceeds 1.0 mm/min, shear strength decreases with increasing rate. The statistical damage constitutive model effectively captures the strain-softening characteristics of the sliding-zone soil, with the Weibull distribution parameters k and λ reflecting the soil’s elastic-plastic properties and degree of strain-softening, respectively. This study provides a theoretical basis for understanding the evolution mechanisms of reservoir-induced landslides and for developing effective mitigation strategies.

Key words: clayed sliding-zone soil, water content, shear rate, shear behavior, damage evolution