A Composite Pressure Relief Method Based on Roof Cutting and Fracturing Expansion for Thick Hard Roofs in Large Mining Heights

In coal mining, thick and hard roof strata are widely distributed, posing significant hazards that easily lead to various issues such as extensive deformations of the surrounding rock and failure of support systems due to strong mining pressure, resulting in frequent safety incidents. Particularly under conditions of large mining heights, the goaf height increases, exacerbating the problem of strong mining pressure on thick and hard roof strata. To address this issue, this paper proposes a composite pressure relief method (CPRM) based on roof cutting and fracturing expansion for thick hard roof in a large mining height. The pressure relief mechanism of this method is analyzed. Moreover, through numerical simulation and field tests, the pressure relief effect of this method is studied, validating its effectiveness. The research results indicate that the CPRM severs the hanging roof of thick and hard strata, promoting the timely collapse of the roof in the goaf, while enhancing the fracturing and expansion filling effect. This effectively reduces the stress intensity in stopes with thick and hard roof strata at high mining heights, significantly addressing issues such as extensive deformation of surrounding rock in roadways caused by strong mining pressure. It provides a reference for pressure relief and control of surrounding rock under similar conditions.