Research on reasonable width of coal pillars between caverns of Wongawilli mining

In order to solve the problem that the unique coal pillar between the mining tunnels of the strip-type "Wongawilli mining" affects the stability of the roof during mining, restrictsthe efficient mining and safe withdrawal of continuous mining equipment, and reduces the recovery rate of coal resources, the Shengping coal mine was used as a research case. FLAC3D numerical simulation research method was used to analyze the stress of the coal pillar, the distribution of the plastic zone of the coal pillar, the stress of the plastic zone of the direct top, the stress of the coal pillar under the scheme of the coal pillar with different widths of 1 m, 1.25 m, 1.5 m and 1.75 m were analyzed. The relevant laws of the influence of coal pillars between the strip-type “Wongawilli mining” mining tunnels on the recovery were obtained. The research results show that the coal pillars between the tunnels are within the conventional size range and cannot be prevented from entering the plastic zone by increasing the width of the coal pillars. With the increase of the width of the coal pillar between the tunnels, the bearing capacity increases, which better ensures the safe mining of the tunnel behind the coal pillar between the tunnels and the reduction of the plastic zone of the coal body on the side of the gob in the leading section of the roadway.. With the increase of pillar width, the subsidence of roadway roof decreases gradually, but the control effect of the width within the range of 1.25 m to 1.75 m will not be significantly enhanced, and the overall movement law of direct roof can not be changed by increasing pillar width. With the increase of pillar width, the area of damage of basic roof will be greatly reduced. There is no significant difference in the change law of plastic zone between the basic roof and the bottom, but the size of the zone is different, which indicates that the wider coal pillar between the mining pits has a higher bearing capacity, but it is difficult to change the evolution rule of the “large structure”of the stope. When the width of the coal pillar between the mining tunnels increases, the working resistance of hydraulic support pillar decreases approximately linearly, and it has no effect on the stress peak of the quadrangular irregular coal pillar in the adjacent branch roadway.