Research On Improving Mining Limit Of Coal Seam No.3 In Caiyuan Mine

Increasing the pillars within the upper limit of mining do much better on releasing coal resource , increasing recovery percent and better economic returns. So that it has become the hot topic and be paid close attention by experts not only in but also out. In this paper , in response to the specific mining condition of Caiyuan Colliery , we did a series of research, and get a lot of important conclusion.The key point of increasing the pillars within the upper limit is how to design the rational placement of pillars. The upper broken rock stratums can be classed three straps, and they are caving strap, crack strap and slow-subsidence straps. According to theoretical calculate and water surge and lithology condition when digging into 3 coal, the maximal height of the crack strap is not attach to Quaternary alluvium. According to the calculation we can know that when the mining height is 8.4m, the maximal height of the crack strap is 23-31.9m.At present technique of TV imaging detect, technique of electricity reconnoiter and technique of electric wave reconnoiter are abroadly adopted in determining mining limit. So in this area the height of waterproof coal pillar is 25.7m.In this paper we also did the analyse of how to design the water protecting pillars of around the fault and made decision of the width of the pillar. At last we choose the 45m as the dimension of the waterproof pillar. In the same way, using the calculate formula of height of upper rock stratums. We make the result that the dimension of the waterproof pillar of Tiangang Fault.