Occurrence mechanism of strong mining tremors under mining near goaf in deep mine with extremely thick strata

Mining tremors is an inevitable dynamic phenomenon in deep mine mining, in view of the current situation that strong mining tremors occurs frequently in the Erdos mining area under mining near goaf in deep mine with extremely thick strata, we used techniques such as ground detection holes and surface stratum movement monitoring, combined with Reissner Thick Plate Theory and the relative moment tensor inversion method, to study the characteristics of strata rupture transport and the evolution of rupture-induced mining tremors source rupture pattern at the working face, and revealed the occurrence mechanism of strong mine tremor in deep coal with the Cretaceous extremely thick strata under goaf mining. The results show that: during the in the retreating period with no goaf nearby, extremely thick strata has no obvious fissures and the surface settlement is stable, with a maximum settlement of about 0.23 m; during the In the retreating period along with goaf, the fissures develop to a maximum height of 444.8 m above the coal seam in the extremely thick strata, and the surface always reaches the maximum settlement at the source of the mining tremor first, and the maximum settlement of the surface increases rapidly before the strong mining tremor occurs, which is more than 60% higher than the recent one. This indicates that the fracturing and movement of the extremely thick strata was the source of the strong mining tremor and that the instability of the extremely thick strata caused the surface to settle rapidly again as a result of the disturbance of the strong mining tremor. The initial fracturing step of the extremely thick strata is 331.82 m, which is consistent with the actual advance of the working face, and supports that the strong mining tremor was induced by the initial fracture of the extremely thick strata; the initial fracturing step increases gradually with the increase of the thickness of the extremely thick strata; the initial fracturing step increases linearly with the increase of the working face length, and the initial fracture of the extremely thick strata transforms from horizontal “O-X” shape to vertical “O-X” shape. The bottom-up rupture of the rock layer induced by the bottom-up rupture of the mining tremors source changed from compressional and shear rupture to compressional and tensional rupture; with the further increase of the mining area of the working face, the fissure extended to the extremely thick strata, and the tensional rupture of the unstable extremely thick strata was the root cause of the “8•20” strong mining tremor. The findings of the study can provide references for the prevention and control of strong mining tremors under mining near goaf in deep mine with extremely thick strata.