Study On The Law Of Overburden And Surface Movement Deformation In Multi-face Mining In Jinyuan Coal Mine

With the increase of coal resources demand in China,the exploitation of pressurized coal resources under construction,under railway,under water and under pressure water("three-down")has become an effective supplement to China's coal resources.The mining of multi-working face under water body is more complicated than the general mining because of the problem of repeated mining and different crop compensation on the surface,this paper takes the mining of 23 adjacent multi-working face under 23 05,23 on 07,09 and 23 under the Weishan Lake of Jinyuan coal mine as the research object,using theoretical analysis,similar material simulation,Numerical simulation and field measurement are used to analyze the deformation characteristics and surface deformation law of repeated mining overburden in adjacent multi-working face.The main conclusions are as follows:(1)Based on the theory of repeated mining,the initial mining surface subsidence coefficient is mainly related to the deep ratio,in which the rock mass shredding coefficient is the main reason why the maximum sinking value of the surface is less than that of the mining thickness.According to the geological mining conditions of Jinyuan coal mine,the initial mining surface subsidence coefficient of 3 coal seam is 0.69,the surface subsidence coefficient of repeated mining in coal seam is 0.81,the spacing between repeated mining and two layers of coal,the thickness of mining and the initial mining sinking coefficient are related,and the smaller the spacing of coal seam,the greater the sinking coefficient of rock layer The larger the amount,the activation coefficient is 0.17.(2)The simulation of similar materials shows that the stress change of surrounding rock in each working face has undergone three stages of slow change,rapid change and finally stabilizing,and the stress change is mainly concentrated in the mining process,which is affected by repeated mining in 07 working face under 23,The overlying rock in the goaf of the previously stable 23 Upper 07 working face left enough falling space under the rock layer to continue to sink,the cracks continued to develop,two times the condition of off-layer and compaction,23 lower 07 working face after repeated mining,the model crack zone developed 49.6m,and the collapse zone was high 34.8m.The empirical formula of water guide crack belt calculates the influence of repeated mining under 3 coal seam on 3 The height of water guide crack zone in coal seam is 40-59m,considering that the mining space of each working face is relatively small,the height of the actual water guide crack zone is lower than the value obtained.(3)Numerical simulation shows that the settlement and deformation area of overburden after mining in each working face is far more than the mining space,and the repeated mining in 07 working face is caused by the sinking of 23 on the bottom plate of 07 working face,the plastic zone of two working face overlaps with each other indistinguishable,the plastic zone develops again,the shear crack zone appears,the overall strength weakens.Causes the powder sandstone(diaphragm)to break,increases the water inrush probability;23 Lower 07 working face "vertical type" repeated mining causes 23 upper 07 working face Goaf"activation",23 on 07 working face GOAF has stabilized crushing rock mass and voids gradually compressed,resulting in the stable surface point again start sinking,surface sinking,Horizontal movement is relatively more intense,the ripple range increases,the maximum sinking value of the surface is 1084mm.After the surface movement deformation is stable,the maximum sinking value of different buried deep rock formations is nonlinear,and the variation amplitude of the maximum sinking value of the rock layer is gradually slowed down and increased rapidly with the depth of burial.(4)By establishing the surface Movement deformation observatory on the top of 23 and 09 under 23 at 05 and 23 in Jinyuan coal mine,this paper makes a measured surface subsidence under the condition of repeated mining,and draws the corresponding surface movement deformation curve according to the observation data,and analyzes and studies the surface movement deformation law in the process of mining,The surface rock migration parameters under this geological condition are determined by curve fitting.The above research has some guiding significance for the safe recovery of repeated mining face,the prediction of surface subsidence and the reduction of mining damage under this geological condition.