Work out control measures for pillar upward mining of left-over coal, in view of coal floor movement, this paper analyzes theoretical foundation and mechanical properties of mechanical model on coal floor movement of rock strata between coal seams in pillar upward mining of left-over coal and presents a simplified corresponding mechanical condition. Taking into the relation between layer movement and time consideration, the PTh model is used to show its rheological properties. By using a two-dimension model, mechanical model of coal floor movement is set up and both ends of cantilever beam are fixed. Finally, subsiding partial differential equation is induced at different districts in pillar upward mining of left-over coal. After solving the equation, prediction model about law of coal floor movement at different districts is gotten in pillar upward mining of left-over coal, which provides a theory basis for further study on upward mining.
In this paper, the process of upward mining in Baijiazhuang mine is analyzed by the simulation function in FLAC-3D software. Basing on the actual drilling column of the upward mining face in Baijiazhuang mine, the variation of rock pressure before and after upward mining is calculated and analyzed by means of numerical simulation model, and then the deformation and movement of the rock strata between coal seams before and after mining the upper and lower coal are further studied. Finally, the simulation results of studying the rock layer’s mechanical relationship and deformation condition is the same with actual mining.
Based on the occurrence condition of coal seams and the geological condition on coal seam mining in Coal Mine Group Baijiazhuang, after pillar mining the 8th coal seam was well controlled, ascending mining the 6th coal seam, mining process was numerically simulated by FLAC3D,the variation law of displacements field on interlayer strata between the 6th coal seam and the 8th coal seam at different face advance were analyzed. Vertical displacement on rock strata increased gradually from below. A control stratum existed on rock strata and could play a control function for steady of strata movement, which provides a theory basis for further study on upward mining.
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