Cyclic loading-unloading mechanical properties and stability analysis of surrounding rock in shallowly buried roadways

In shallow coal mining projects, the surrounding rock is more susceptible to the movement of overlying strata and mining interference. It is in a cyclic loading-unloading state, which degrades its mechanical properties and easily triggers secondary disasters. To better understand the mechanical behavior, energy evolution, and damage characteristics of rocks under complex cyclic stresses, this paper uses the Zaoquan Coal Mine in Ningxia as a case. It conducts uniaxial compression and cyclic loading-unloading tests on the main lithologies（sandstone, mudstone, and coal seam） of the coal seam roadway surrounding rock. Through systematic analysis of the surrounding rock’s mechanical properties and energy evolution patterns, and by incorporating an energy based perspective, a rock stability evaluation method is established. Results show that cyclic loading-unloading significantly reduces coal seam’s ultimate strength（50.87% drop）, followed by sandstone（10.17% drop）, with minor changes in mudstone strength. After cyclic loading, the elastic modulus of mudstone and coal seam increases, while that of sandstone slightly decreases, indicating significant differences in mechanical property changes across lithologies, with coal seam showing the most degradation. From the energy evolution and damage degree perspectives, sandstone has the highest cumulative dissipated energy but the lowest damage degree（6.17%）, reflecting strong fatigue resistance. Coal seam, despite the second highest cumulative dissipated energy, has the highest damage degree（10.85%）, closely related to its high brittleness index. Mudstone, with low initial strength, exhibits a relatively high damage degree after cyclic loading, having the lowest brittleness index and a milder failure mode. This research offers theoretical support and quantitative indicators for stability assessment and support design in shallow roadway surrounding rock. It aids in optimizing roadway support parameters, ensuring safe and efficient mineral extraction.