Study On High Mining-induced Stress Evolution And Effects Of Downward Relieving Mining For Closed Coal Seams

In recent years, With the increase of mining depth and intensity of exploitation, mining of closed distance coal seams had technical problems which preparation roadway is difficult to support, the roof and floor is difficult to control, rock burst is easy to occur, gas drainage is hard to implement and coal pillar is hard to establish. According to the occurrence characteristics, physical and mechanical characteristics and mining technology characteristics of close distance coal seams(No.8,7,6,5,4seam) mining under typical conditions in west fourth mining region of Paner mine, this paper engages in systemic research on surrounding rock mining-induced stress evolution characteristics and mechanism of high mining-induced stress evolution influence on the surrounding rock displacement, deformation and failure rule in a wide range of stope with the application of the research methods of numerical simulation, similar material simulation, field measurement verified and theoretical arithmetic.First, based on the analysis of much field investigation, data generalization and classified statistics, the UDEC2D numerical simulation and2D similar material simulation models of multi seams(five layers) are designed by using multi stage(2-5times) relieving mining method from up to down to comprehensive analysis the evolution characteristics of displacement field, stress field as well as fracture field, moreover, the mechanisms of multi mining high stress evolution which has dynamic effect on mining induced fracture along with irregular pillar effects on disturbance stress and fracture different morphological evolution were revealed; furthermore, according to mining conditions, the accuracy of the simulation experiment has been verified by the stress-focus phenomenon under pillars and the large deformation characteristics from the field measurements of the pressure behavior and the roadway surrounding rock deformation; finally, on the basis of high stress evolution effects and experimental data statistics of relieving mining for closed coal seams, the released area of the floor evolution model is established, the calculation method for released range of the floor are deduced and theoretical calculation system is perfected accordingly. The research not only provides a theoretical basis for mining power disaster prevention with repeated mining multi-source stress evolution as its leading factor, but also has certain theoretical significance and engineering value for the design and optimization of safety and high efficiency as well as simultaneous extraction of coal and gas under the same condition.