Ground pressure features of roadway under close range goaf in the Xinyu Mine

To study the ground pressure features of roadway under close range goaf,deformation laws of surrounding rock during mining are analyzed by deformation monitoring.Variations of vertical stress in surrounding rock during mining are obtained by numerical simulation.The results show that the convergence between roof and floor can be 2.02-3.09 times that between two side walls.The intense influence area is 10 m front of working face,where deformation velocity can become fast.The two side walls are influenced more significant in this area.Vertical stress in surrounding rock closed to coal pillar increases when adjacent to the working face.It can be found that the existence of goaf make curves no longer obey exponential function to the base.Working face under goaf has incomplete roof.So effects of abutment pressure decrease.The influence scope of abutment pressure is only 5-10 m,which reduces obviously compared to common roadway.The formation of side abutment pressure in upper coal pillars make a roadway under goaf has a larger deformation,and side walls supports are easy to damage because of a compressive expansion in surrounding rock.Roof sinking caused by the damage of support in side walls,and the seepage from goaf will aggravate the heave of Al mudstones floor.