Simulation experiment of overlying strata movement features of longwall with gangue backfill mining

The movement features of overlying strata are different from that of mining by caving method since gob areas are occupied by fillings,and the processes of faces mining and gangue filling were simulated in laboratory by numerical calculations.Stress changes and movement features of overlying strata were simulated under different filling ratio conditions by the approaches of changing the initial support power,working resistance of support,and tamping forces of filling material,then by combining field measured results,the regularity of overlaying strata was revealed.And three main conclusions were drawn in this research as follows:working resistance of support play a significant role to the filling effects,high initial power and working resistance of support can restrict deformation of roof and ensure enough time to fill more filling materials to gob area,thus can decrease the height of gradual subsidence zone and regulate surface deformation.Immediate roof is regulated by gob area's filling materials,which can control the deformation,subsidence and caving of immediate roof.Rupture and collapse are the main forms of immediate roof.And then it arranges in good order on goaf waste rock after collapse.Forms of main roof,which correspond to immediate roof shifting,are in curve subsidence types.Besides,the collapse height of overlaying strata will reduce strikingly.