Abstract: For the problem of pressure burst disaster in step region of unequal length working face in Yangcheng coal, based on the special arrangement mode of working face and overlying strata characteristics, the theoretical analysis, numerical simulation and field measurement are adopted to analyze the dynamic evolution process of surrounding rock stresses and the movement characteristics of overlying, and the mechanism of pressure burst in step region has been investigated. The results show that: the overlying strata in step region experiences a complex evolution of “OX-S-C”, when it is converted from OX to S, large area of roof rock is breaking and sinking, in large area of roof rock, and the higher the height is, the greater the length of cantilever beam over step region is. Influenced by the overlying rock movement and the mining stress field, the coal and rock mass form a high stress concentration area. The coal-rock mass is suddenly destroyed with releasing elastic strain energy under the action of dynamic load of roof rock, and the pressure burst occurs. The strain energy distribution characteristics are investigated by using software COMSOL under different drilling parameters, and the parameters of drillhole pressure relief are optimized. According to the simulation results, with the increases of borehole diameter, depth and decreasing spacing, the pressure relief effect is more obvious. Considering the engineering application, diameter of 150 mm, depth of 30 m and spacing of 1 m are regarded as the reasonable drilling parameters. This method is applied to the prevention of pressure burst in step region of working face 1302 in Yangcheng coal, and good prevention results have been achieved.

Key words: unequal length working face, step region, pressure burst, overburden strata movement, drillhole pressure relief