Research Of Ground Subsidence And Reducing Subsidence By Filling In Multi Seam Mining Under Power Structure

A big amount "three unders" coal exists in China,and the normal production of mine and environmental protection is always disturbed by the overlying strata movement and deformation of ground surface subsidence,in the case that there are structures on the ground,which causes further difficulty in underground mining,the issue of technology and economy is very prominent.Under the trend of green environmental protection in contemporary mining areas of mining,how to arrange the mining scheme based on the coal seam,the rock geological conditions and the ground construction distribution,to achieve the underground mining safety,stability of ground facilities,reasonable exploitation of coal seam,treatment of mined out area and strata control is valuable.In this paper,combined with the mining engineering background in No.4,No.5,No.8,No.9 coal seam of Shanxi Shuozhou coking coal mine,according to the arrangement and distribution of ground electric tower and wire,the current feasible mining reducing subsidence methods and the key strata theory are researched,considering the green mining method based on the theory of key strata.By the method of theory calculation,numerical simulation and field observation,the stability rock strata and surface subsidence degree by different mining methods is analyzed,the optimization of mining method based on the influence to power structures is done,the research has reference value for the stability of earth’s surface under the influence of mining.According to the actual geological conditions of coal seam,the applicability and effect of mining plan is analyzed,using the FLAC3D numerical software to simulate the migration of overlying strata and ground during multi seam mining,the key layer stability and degree of movement and deformation on ground under the conditions of caving method,strip mining and strip filling mining is discussed,considering from the rock stability,surface subsidence control and recovery factors,using a new kind of green mining technology,reducing subsidence law by filling mining in multi coal seam is studied,through analyzing the curve of deformation and displacement,characteristics and key parameters of subsidence basin under different mining schemes in each coal seam.Specific conclusions are as follows:(1)In multi coal seam downward mining process,with the increase of the accumulated coal mining thickness,the strata and ground subsidence and horizontal displacement is increasing,the roof and ground movement deformation phenomenon caused by multi seam mining is more obvious.All filling mining can be considered in upper coal seam,compared with the caving method,the ground subsidence and the horizontal displacement decreases after the filling mining.Based on all backfill mining used in the upper coal seam and the stability of key layer,using conventional strip mining or strip fill mining can play a good subsidence reducing effect in lower coal,ensuring the stability of key stratum.(2)The mechanical models of narrow coal pillar and strip coal pillar are established by the analysis of stress situation and constitutive relationship of coal pillar in strip mining.Considering the constitutive relation of coal pillar with nonlinear weakening,a cusp catastrophe model of narrow coal pillar and strip coal pillar instability is established.The essential condition of the instability of coal pillar was obtained by the analysis of the mutation model,the calculation formula of burst compression of two kinds of coal pillar is derived.(3)According to the actual geological condition of multi coal in seam coal mine,mining influence analysis and numerical simulation research,the width of strip is designed as 50m in conventional inclined direction strip mining.In the strip filling mining,leaving 60m filling strip-coal pillar support,filling strip is 40m,the author puts the three mining program:No.4,No.5 coal caving coal mining,No.8,No.9 coal conventional strip mining(scheme one),No.4 coal full filling mining,No.5 coal strike belt mining,No.8,No.9 coal inclined strip mining(scheme two),No.4 coal full filling mining,No.5,No.8,No.9 coal strip filling mining(scheme three).(4)After using caving mining in No.4 and No.5 coal,due to the destruction of key layer,the ground subsidence maximum is 5.74m,the tilt value maximum reached 24.14mm/m,exceed the allowed movement deformation range.The simulation of whole filling mining in NO.4 coal is done,compared with plan 1,ground subsidence and deformation values reduced significantly,after the No.5 coal mining,subsidence growth is slow,severe subsidence phenomenon doesn’t appear,after No.8 and No.9 mining in lower coal,the largest tilt value does not exceed 2mm/m in a static sink basin,the control of ground subsidence and protection of key strata in scheme 2,3 is superior scheme 1.(5)The ground remains stable after all filling mining used in the upper coal seam,under the premise of ensuring key layer stable,the coal pillar and filling strip common support the roof in strip fill mining and the effect of reducing subsidence is similar to conventional strip mining,the recovery rate was significantly higher than that of strip mining.