Variation characteristics of support strength and stability in post-peak large deformation for roadways surrounding rock.

The stability of deep underground roadways is critically challenged by post-peak large deformations of surrounding rock, especially under high in-situ stress conditions. To investigate the evolution characteristics of support strength required to maintain roadway stability throughout the post-peak deformation process, this study integrates physical similarity simulation, numerical simulation, and field monitoring. A novel laboratory testing system with adjustable support force and deformation was developed to simulate varying rock strength conditions. Three typical rock strength scenarios were reproduced using optimized gravel-sand-gypsum material ratios. Numerical simulations were conducted using a fractured rock mass flow model to capture post-peak mechanical behavior. Field tests in a deep coal roadway verified the deformation-support inter-action under long-term loading. The study identifies six distinct categories of support force-displacement relationships, including linear decline, negative exponential decay, and fluctuation-dominated responses. These findings provide a systematic understanding of roadway rock-support interaction mechanisms under large deformation, offering practical guidance for optimizing support design and ensuring long-term roadway stability in deep mining environments.