A Study Of Load Transfer Law Of Overburden In Strip Filling Mining In Shanghe Coal Mine

Room-pillar mining was widely used in the early stage of small and medium-sized coal mines in northern Shaanxi.Long-term creep of coal pillars resulted in large-scale instability of bearing structure of"surrounding rock-coal pillar group".Therefore,it is considered to adjust the unexploited solid coal to strip filling mining.Taking Shanghe Coal Mine in Yulin City as the research object,the parameters of strip filling mining and the law of overlying rock load transfer are studied by using the methods of theoretical analysis,physical similarity simulation.numerical simulation and field practice.In the process of strip filling mining,overlying rock load needs to be transferred slowly and evenly to the filling body.The whole filling mining process in Shanghe Coal Mine is divided into three stages:benchmark strip mining and filling,even strip pillar mining and filling,odd strip pillar mining and filling.Based on Winkler s elastic foundation theory,the mechanical model of "coal pillar-roof" is constructed,the deflection formula of the post-mining roof is deduced,and the mining parameters of"mining 7m to retain 8m"in strip face are calculated,and the load of the post-mining strip pillar is estimated to be 6.45MPa.Similar simulation results show that the overlying strata load mainly transfers to the remaining strip pillars after strip mining in the first stage.The average abutment pressure of the pillars increases from 2.51 MPa to 4.10MPa,and there exists a bearing structure between the overburden and the strip pillars.After the second stage even-numbered pillars are filled,the overlying strata load is mainly supported by the odd-numbered strip pillars,and the pillars are supported by the remaining odd-numbered pillars.The average pressure is 5.5MPa;after filling the third stage odd number coal pillar,the overlying rock load is mainly supported by the first stage strip filling body,the average abutment pressure is 2.76MPa,and the third stage filling body is basically not loaded.The results of numerical simulation show that the first and second stage plastic yield zones are mainly distributed in the side of strip pillars,and the third stage plastic yield zones are mainly distributed in the boundary and section pillars.The evolution of vertical stress in stope shows that the main bearing body of overlying strata load in the first stage is 8 m wide strip coal pillar,and the main bearing body in the second and third stages are even numbered coal pillar and filling body in the first stage respectively.The law of overlying strata load transfer is basically consistent with similar simulation.Industrial test takes 3216 working face of Shanghe Coal Mine No.2 panel as an example,and chooses aeolian sand,fly ash,cementing material and additives as filling materials.After 28 days of solidification,the filling body contacts well with the top coal and there is no empty roof phenomenon.The stress monitoring of strip filling shows that after the third filling stage,the average abutment pressure of the first and second filling stage is 2.45MPa and 1.5MPa respectively,and the abutment pressure of the filling body is less than the safe bearing strength.The study on load transfer law of overlying strata in strip filling mining in Shanghe Coal Mine provides theoretical support for strip filling mining in medium and small coal mines in Yuyang District,and has important significance for the protection of ecological environment in this area.