Abstract
In view of multiseam mining under goaf, the surrounding rock control problem of lower coal roadway will be affected by concentrated coal pillar left in upper coal seam goaf and dynamic pressure superposition of working face in this coal seam. Under the geological environment of No. 16 extrathick coal seam in the Laoshidan coal mine and taking the working face 031604 as the research background, the reasonable docking position selection of the withdrawal roadway and the docking roadway in the middle mining period and the surrounding rock stability control problems of the withdrawal roadway and the docking roadway during the final mining period were studied by using the methods of field theoretical analysis, numerical simulation, and field measurement. The mechanical mechanism of the nonuniform failure of the retreating roadway and the docking roadway during the final mining period is shown, and the control method of the surrounding rock stability of the roadway is put forward and applied. The results show that (1) through the analysis of the superimposed stress under the concentrated coal pillar and the coal seam in advance, the specific butt joint position is arranged at 860 m away from the open-off cut, which is 10 m away from the goaf of No. 12 coal seam. (2) With the working face 031604 advancing through the process, the deviatoric stress value of the withdrawal roadway gradually increases, the maximum principal stress of the two sides of the roadway deflects clockwise from the vertical direction to the horizontal direction, its angle also gradually increases, and the shape of the plastic zone gradually expands from symmetry to asymmetry. (3) It is revealed that the peak value of deviatoric stress on both sides of the docking position of docking roadway increases gradually under the influence of mining and deflects anticlockwise to the vertical direction with the principal stress angle. The joint action of both is the mechanical mechanism that causes the plastic zone to expand in an asymmetric shape. (4) The coordinated control scheme of support (anchor bolt and anchor cable)—modified (grouting)—is adopted for the withdrawal roadway, and the coordinated control scheme of support (anchor bolt and anchor cable)—changing the cross-section shape of the roadway—is adopted for the docking roadway. The purpose of the smooth connection of working face and rapid and safe withdrawal of equipment is achieved on site.
Highlights
Coal is the conventional energy with the largest reserves and widest distribution in the world
(2) With the working face 031604 advancing through the process, the deviatoric stress value of the withdrawal roadway gradually increases, the maximum principal stress of the two sides of the roadway deflects clockwise from the vertical direction to the horizontal direction, its angle gradually increases, and the shape of the plastic zone gradually expands from symmetry to asymmetry
Field practice and research show that [1, 2], when mining multiple coal seams, deep coal roadway is often affected by the coal pillars left by the overlying coal seam and the dynamic pressure of the working face of the coal seam [3], especially in the case of extrathick coal seam, which makes the maintenance of roadway and roof management of working face more complex and difficult at the lower coal seam, and which are easy to cause roof fall, spalling, and other accidents; this situation seriously threatens the safety production of the mine
Summary
Coal is the conventional energy with the largest reserves and widest distribution in the world. Su et al [7] studied the stress distribution regularity of lower coal seam, deformation failure mechanism of the roadway group, and surrounding rock stability control and put forward the optimized support scheme of the arch section for a roadway in a highstress area under coal pillar. Through the influence range and degree of concentrated coal pillar on the stress of lower coal seam when the working face is not mined, the reasonable docking position is judged, and the stress distribution and dynamic evolution law of plastic zone of surrounding rock of docking roadway and withdrawal channel are analyzed, the mechanical mechanism of nonuniform failure of roadway surrounding rock is revealed, the supporting methods and measures are put forward, and industrial practice is carried out. The research results have guiding significance to solve the surrounding rock stability control of mining roadway under such conditions
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