| The serious accidents are mainly caused by gas outburst and water inrush in our country’s coal industry.Casualties and economic losses caused by water inrush were extremely heavy to coal enterprises.Mining above confined aquifer has been the focus and difficulty of coal mining.In recent years,paste backfilling has been widely applied because of its safety and efficiency with the development of special mining technologies.This technology can ensure the safety of mining under water body,building,rail and above confined aquifer.The mining of lower coal seam is above confined aquifer in Daizhuang colliery.Therefore,paste backfilling is put forword.This paper analyze the failure rule of coal seam floor in backfill mining with the comprehensive use of theoretical analysis,numerical simulation and field measurement.And get the process parameters of paste backfilling include the ratio of filling material.The article acquires the following main research results:(1)Theoretical results show that the maximum failure depth of 11605 working face is 11.7 m in caving mining.Both of thirteen limestone and ordovician limestone’s water inrush coefficients are greater than 0.1 MPa/m.The caving mining is of great dangers.(2)Beam model of water-resisting layer is adopted in backfill mining.According to the numerical simulation results,the floor failure depth in backfill mining is 4~9 m.The design parameters of backfill mining are as follows,the strength of the filling body is 2 MPa,and the filling step is 3.6 m.(3)In this paper,PLS model is used to design the ratio of filling material.Not only the results can meet the strength requirements of filling body,but also reduce the filling cost.Water injection test shows that backfill mining can reduce the depth of floor failure,and prevent water inrush.Results of this study,not only have practical significance to safely mining of lower coal seam in Daizhuang colliery,but also can be used as the reference to other similar coal mines above confined aquifer. |
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