Study On Overburden Movement Rule In Strip Coal Pillar Filling Mining

In recent years,as the country has actively carried out environmental protection,elimination of outdated production capacity and integration of high-quality resources are the country’s long-term policies for the exploitation and utilization of coal resources.Paste-filling mining technology is used as a solution to the coal resources under-building,under-railway,underwater,under-construction and confined water.As one of the green mining technologies has been widely used.This paper takes the recovery and mining of the coal pillars from the remnant strips of the Daizhuang coal mine in Jining,Shandong,and uses the 2351 filling work face as the research object.It adopts theoretical analysis,numerical simulation,similar materials test simulation and field measurement and other methods to apply the study.During the process of paste filling mining,the roof movement rule of the working face and the stress deformation characteristics of the filling body are analyzed.The relationship between the filling rate and the deformation and damage of the overlying rock in the paste filling mining process are studied,with the help of field measurement and surface movement.Deformation is expected to obtain the control effect of filling and mining on surface subsidence and achieve the following main results:(1)Theoretical analysis of the flexural subsidence deformation of the roof and the supporting force relationship provided by the elastic foundation “coal body and backfill body” to the roof are obtained through force analysis.The three main influencing factors of the roof subsidence are divided in order of degree of influence.Roof subsidence before filling,the elastic modulus of the filling body,the roof conditions.For the 2351 working face,when the elastic modulus of backfilling body is 0.2 GPa,roof subsidence before filling is 100 mm,the height of roof rock beam is 4 m,and the elastic modulus of the roof is 35 GPa,the amount of roof subsidence is about 130 mm.(2)Numerical simulation of the paste filling mining face,the roof subsidence value can be controlled within 350 mm,and the overburden vertical stress range is 10-15 MPa.The stress-strain growth of paste backfill presents three phases: rapid growth phase,slow growth phase,and stable molding phase.The vertical displacement of backfill is controlled within the range of 250 to 500 mm.(3)Similar simulation experiments confirmed that there is no “vertical three belt” feature in the immediate roof of working face,and the filling rate is the main influencing factor of surface deformation caused by the mining method.When the filling rate of paste filling mining reaches above 95%,the immediate roof only shows bending zone characteristics.When the filling rate is maintained at about 90%,micro cracks begin to appear on the roof.When the filling rate is less than 85%,the roof plate is broken through.The overburden formation is basically similar to the caving mining method.The height of caving and fracture zone is small.(4)Analysis of data collected on the spot are consistent with the numerical simulation results.The ultimate backfill stress will be stable at about 10 MPa,which is the original rock stress value,and the backfill body compressed deformation is about 100 mm.By analyzing surface deformation observation assisted subsidence prediction software to obtain surface deformation data,it is proved that the recovery of strip coal pillars by filling mining method can control the surface building damage within the scope of the specification requirements.