Analysis of the influence of different rock (soil) bodies on the failure characteristics of overlying rock in Yushen mining area

In order to analyze the influence of different rock ( soil ) bodies on the failure mode of overburden rock in Yushen mining area, three types of overburden rock structures, including red soil-weathered bedrock-normal bedrock, weathered bedrock-normal bedrock and normal bedrock, were selected in the range of mining-induced cracks. The development degree of mining-induced cracks in soil layer and bedrock was observed by water pressure test method and leakage observation method respectively, and the failure height and saddle-shaped alienation characteristics of overburden rock under different rock (soil) structures were compared and analyzed. The results show that when there is red soil or weathered bedrock near the top of mining-induced cracks, the ratio of the failure height of mining-induced overburden to the thickness of coal seam mining is between 9.95 ~ 11.65 and 12.21 ~ 15.55, respectively, which is significantly smaller than that of normal bedrock (18.10 ~ 19.41). Red soil layer or soft rock overburden is helpful to inhibit the development of mining-induced cracks. The greater the difference between the compressive strength, tensile strength and shear strength of the rock mass near the top of the mining crack, the more obvious the 'saddle-shaped' alienation characteristics of the overlying rock failure under the influence of mining. Compared with the weak or very weak type of overburden failure range, the overburden failure range corresponding to different rock (soil) structures in Yushen mining area is obviously larger.