Abstract
Layered rock masses are extensively distributed in nature. Investigating the mechanical response characteristics of soft-hard interbedded rock masses holds significant theoretical implications for practical engineering applications, such as landslide prevention and roadway support. This study uses the numerical simulation software PFC2d to simulate the progressive failure process of a soft and hard interlayered rock mass under various degradation conditions and examines the effects of layer inclination angle (β) and strength degradation on the strength and failure characteristics of this interlayered rock mass. The results showed that the stress-strain curve of soft-hard interbedded rock masses can be divided into four stages: elastic deformation, stable crack propagation, unstable crack propagation, and post-peak stage. Under various working conditions, the peak strength of soft-hard interbedded rock mass shows a U-shaped trend with the increase of inclination angle. The peak strength change rate after strength degradation of soft and hard rocks is defined. The samples with β ranging from 0° to 90° are divided into soft and hard rock co-control area, hard rock main control area, soft rock control area, soft rock main control area and soft rock single control area according to the change rate. The reason for the change in failure mode of soft-hard interbedded rock mass is attributed to the change in inclination angle, and its influence mainly depends on the initiation and propagation forms of microcracks. Ultimately, the trend of microcrack formation in relation to strain was categorized into five distinct phases. This study examined the relationship between the degradation of soft and hard rocks, the number of microcracks, and the strength characteristics of rock masses at various inclination angles from a microscopic perspective. The findings are critically important for assessing the stability of interbedded soft and hard rock formations and for designing appropriate engineering interventions.