The Tingnan Coal Mine belongs to one of the large-scale coal mines in the early stage of mining in Binchang Mining Area of Huanglong Coal Field, with complicated geological conditions and "three thick and one hard" features. Mine mining No. 4 coal seam depth of about 600m, the average thickness of the coal seam 18.3m, mining coal seam overlying endowed Cretaceous thick hard sandstone thickness of 342.15m, the surface for the thick humid loess overburden with an average thickness of 150m, with the expansion of the mine mining depth and scope of the coal bed roof power disaster is a serious threat to the safety of mine mining. This paper takes the geological conditions of the coal seam and the structural characteristics of the overburden in the second plate area of Tingnan Coal Mine in Binchang Mining Area as the research object, and adopts the combination of theoretical analysis, physical similarity material simulation, numerical simulation computation and on-site measurement to study the formation mechanism of the power disaster of the working face of the thick coal seam mining in the high level of thick and hard rock layer, and puts forward the corresponding preventive and control measures and technological pathways. The main research content of the paper includes:
(1) Combined with the physical and mechanical properties of rock strata, we analyzed the structural characteristics of "three thick and one hard" overburden rock in Tingnan Coal Mine, and applied the key layer theory to analyze the loading of thick loose loess layer, the energy accumulation of bending and deformation of thick hard rock strata, and the impact conditions of violent movement of the overburden rock of thick coal seam mining in combination with the law of manifestation of the ore pressure, the law of deformation of the roadway, and the law of moving and deformation of the surface of the ground, so as to determine the mechanism of the manifestation of the impact pressure in the face and the main disaster-causing factors.
(2) Based on the SMP damage criterion, a theoretical calculation model of section coal pillar stability in Tingnan Coal Mine is constructed, and the critical criterion for the stability of section coal pillars in multi-face mining is calculated. Through similar material simulation experiments and numerical simulation calculations, the movement and deformation laws of overburden rock for mining and leaving different widths of section coal pillars in the high level and thick hard rock stratum are analyzed and given: the low key layer is damaged in the form of beams to form a "Under the condition of leaving the section wide coal pillar, the low level structure formed by each working face is relatively independent, and the high level main key layer is in the form of wave under the support of coal pillar; under the condition of leaving the section narrow coal pillar, the narrow coal pillar is destroyed and failed with the mining of working face, and the high level main key layer is fully sunk in the form of gentle basin after mining of several working faces. After several working faces are mined, the high-level main key layer fully sinks in the form of a gentle basin.
(3) The experimental results show that the energy of the strong impact ground pressure in the working face mainly comes from the accumulated energy released by the fracture of the low rock structure above the coal pillar in the section, which is consistent with the observation results of the mine pressure. Based on the improved Winkel's foundation theory, a calculation model of supporting pressure under the condition of multiple key layers was established, and the calculation model was applied to the working face of Tingnan Coal Mine's second plate area to analyze the distribution law of supporting pressure, and semi-quantitatively analyze the energy released by the breakage of each key layer, which led to the disaster-causing mechanism of multi-working face mining under the high-level thick and hard rock layer in Tingnan Coal Mine: the wide coal pillar of the section and the overlying thick and hard rock layer form a stable energy-concentrating structure for bearing, and the high-level key layer is in the thick loose-loaded layer, and the main key layer is in the thick loose-loaded layer. The main key layer undergoes bending and deformation under the action of thick loose loading layer and self-weight, and a large amount of energy is accumulated in the rock layer overlying the wide coal pillar of the section. When the mining space reaches the limit state, the low sub-critical layer structure above the coal pillar that has not collapsed breaks, forming a roof dynamic disaster.
(4) Based on the mechanics of materials, a structural stability discrimination model of low-level overburden rock in working face mining was constructed, and the boundary of the rock layer that has not collapsed in the hollow area was approximated as a trapezoidal arch beam, and the tensile stress, extrusion stress, and shear stress at any point in the trapezoidal arch beam with constraints on the two sides were given, and the necessary conditions of the structure for no destabilization were solved according to the strength criterion; a mechanical model of the thick plate of the high-level overburden rock was established, and a finite integral transformation was applied to solve the analytical solution of bending deformation of the thick plate on the Vinckel foundation model. The analytical solution for the bending deformation of the thick plate on the Kerr foundation model was developed, and the limiting height of the working face mining was given. On the basis of this model, a multi-working face mining overburden structure stability discrimination model was constructed, and the destabilization process of "thick hard rock layer - section coal pillar structure" was analyzed.
(5) In view of the characteristics of power disaster in Tingnan coal mine, the analysis puts forward the corresponding disaster prevention and control mining layout and countermeasures: the width of coal pillar in section is less than 8m, the thickness of coal seam mining is less than 9m, the width of working face mining is more than 200m, and the working face is mined in sequence, so as to realize the effect of the destruction of coal pillar in section in sequence, and the overburden of rock layer is slowly sinking in sequence, and the overburden of rock is transferred to the hollow area, and the effect of preventing and controlling the power disasters is realized through the adjustment of the layout of mining in the working face.
The research results have revealed the transportation law and disaster-causing mechanism of mining overburden under the condition of high thick and hard rock layer in Tingnan Coal Mine No.2 Plateau Area, put forward the measures of preventing and controlling the roof disaster, and carried out good application practice in No.3 Plateau Area, which can provide the basis for the safe mining of the large mining face with deep and thick hard roof.
谷歌
火狐
