Research on the time-varying mechanism of energy dissipation structure of overlying strata under the influence of mining height

The mining-induced deformation and failure of overlying strata were investigated through numerical simulation, with Liuhuanggou Coal Mine selected as the case study. This research was carried out through simulation. The evolution trended of delamination amounts all present five stages: “rapid increase-decrease-continuous fluctuation-increase-rapid decrease”. The maximum order of the delamination amount at different coal seam mining heights was: 6 m > 4 m > 2 m. The fracture penetration degree generally shown a downward trend. Based on the experimental results, it was found that the mined-out area consists of the overburden compaction area, the gas migration area and the gas reservoir area through characteristic parameters. The energy structure in the overlying rock of the pressure relief gas transportation and storage area was defined based on the principle of minimum energy. The “half-moon” shape was established. The criterion for determining the fracture of the energy dissipation structure under the influence of the pile height had been derived. The drilling layout revealed that the middle layer gas drainage borehole had the best effect. The drilling layout was optimized. The methane plot ratio of optimized gas drainage boreholes increased from 3.1 % to 9.56 %, and the total gas drainage volume increased from 56.88 m 3 /min to 174.14 m 3 /min. The average gas volume fraction of the return airway, the upper corner and the working face was all less than 1%. The results of the study provided guidance for the drilling.