Abstract:
In order to grasp the overburden breakage and fissure evolution law of thick coal seam mining, a three-dimensional physical similarity simulation experiment platform was built with the background of E2306 working face of Gaohe Energy, and a combination of distributed fiber optic sensing technology and borehole peeping monitoring was used to clarify the overburden breakage and fissure distribution characteristics. Combined with the thin plate bending theory, the structural mechanics model of overburden rock in the quarry was established, revealing the mechanism of overburden rock fissure induced under the influence of mining overburden rock breakage, and deducing the regional development pattern of mining fissure. The results show that: after the face is mined back, the total number of pressures is 7 times, and the development height of the collapse zone and fissure zone is 39 m and 71 m respectively, which is consistent with the field results of the face, and matches with the theoretically calculated values, which is in line with the actual situation of the mine. In the height of the collapse zone, the low near-field overburden rock is broken vertically in a “pair of fan-shaped” way, with the structural breaking movement of “towards the cantilever beam-inclined to the masonry beam” as the main, with a large number of longitudinal breaking fissures developed, and transverse horizontal shear intersecting fissures accompanied. The overburden rock is gradually broken from the bottom up, and the overburden rock in the high far field within the height of the fissure zone is transversely broken, with the structural breaking movement of “towards masonry beam-inclined masonry beam” as the main movement, and a large number of transverse horizontally tensile delaminated layers are developed. The number of overlying rock fissures in the boundary area of the mining airspace shows the change rule of increasing and then stabilizing with the advancement of the working face, and the change of the number of strike fissures is parabolic; the number of overlying rock fissures in the middle area of the mining airspace shows the change rule of increasing and then decreasing with the advancement of the working face, and the change of the number of strike fissures is saddle-type. After the overburden rock breaks and pressurizes, the central part of the mining zone continues to bear pressure, and the rock layers on both sides are sheared and damaged to form shear concave area and bearing concave area, and the scope of the area expands with the bending and breaking of the overburden rock at different layers. The development pattern of the mining fissure area evolves from an elliptical parabolic zone to an elliptical parabolic zone with concave ends, and finally to an elliptical parabolic zone with concave ends and top.