Breakage mechanism of roof strata above widespread mined-out area with roadway mining method and feasibility analysis of upward mining

In order to reveal the breakage mechanism of roof strata in roadway mining,a continuous deep beam model under uniformly distributed load was established and its stress distribution was analyzed. Based on the mechanical properties of roof strata structure,the determination theory and method of upward mining above widespread mined-out area of roadway mining was proposed,and the influence height of No. 8 coal seam in Hulonggou colliery is 8. 8 m by theoretical calculation. The feasibility of roadway mining of No. 5 coal seam was further studied using FLAC2D soft- ware. The results show that the height of stress weakening factor contours increases as the number of strips increases, however,when the number of strips is greater than four,the stress weakening factor would not increase any more,and the influence height of No. 8 coal seam in Hulonggou colliery is 10 m. Theoretical calculations and numerical simula- tions show that the influence height of No. 8 coal seam in Hulonggou colliery is less than 25 -30 m,the coal layers spacing,so upward mining above widespread mined-out area is feasible.