Study on characteristics of underground mine pressure and surrounding rock control in 8.2 m ultra-high mining height stope

In order to study the occurrence of mine pressure in the near-shallow buried and super-large mining height working face,the No.12-2108 working face of the Jinjitan Coal Mine was used as the engineering background,and the online real-time monitoring and theoretical calculation of the mining pressure was used to comprehensively mine the 8.2 m ultra-large mining height. The characteristics of mining pressure in working face and the control measures of surrounding rock were studied. It is concluded from the study that the roof structural composition is the core of the changes in the movement law of the overlying rock. The thickness of the direct roof is thin and falls with the mining,and it cannot fill the gob. The basic top rock beam is a multi-rock beam with an internal stress field structure,and the end is cut to form an “equivalent direct top”,which is mainly manifested as a double key rock beam structure. The fracture of the lower key rock beams results in a small period of pressure (step distance of 15 m and pressure strength of about 30 MPa). Simultaneous fracture and superposition of the key rock beams of the formation resulted in a large period of pressure (the step distance is 31 m,and the pressure of the pressure is about 46 GPa). Cyclic compression showed characteristics of a large and a small cycle. Generally,the large period of compression is 2 times that of the small one. In the field monitoring,the initial pressure step distance reaches 98-117 m,and the periodic pressure step distance is about 22 m on average. The measured results are basically consistent with the theoretical analysis. The increase in the thickness of the “equivalent direct roof” of the cantilever beam basically falls with the working face,reducing the rotation space of the main roof key rock beam,forcing the basic roof hinge point to move up,and delaying the compressive strength of the basic roof key rock beam. Aiming at the occurrence law of mining pressure in fully-mechanized mining face with super large mining height and the bearing characteristics of supports,control measures such as reasonable control of mining height,acceleration of the advancement speed of the working face,increasing initial support force of supports,and a three-level protection board were effectively adopted at the site to effectively avoided near-shallow buried super-large mining high-end surface leakage,bench subsidence and large-area coal wall-related disasters. The working conditions of the fully-mechanized mining support with large mining heights satisfactorily met production requirements.