Influence of hydraulic fracturing parameters of reused coal pillar roadway on pressure relief effect

Hydraulic fracturing pressure relief technology is used to control surrounding rock deformation of reused coal pillar roadway. In order to determine parameters of hydraulic fracturing, 43122 reused coal pillar roadway of Changping Coal Mine of Shanxi Jincheng Anthracite Mining Group Co., Ltd. was taken as research object, influence of fracturing times and fracturing positions on pressure relief effect were numerically simulated by use of plane discrete element UDEC software. The results show that the longer the fracturing segment length is, the less the corresponding fracturing times will be, and the weaker the effect of hydraulic fracturing on roof will be. Fracturing segment length should not exceed 4 m. Fracturing borehole will increase stress of coal pillar when it is located at coal pillar side of lower section working face, and reduce stress of coal pillar when it is located at goaf side of upper section working face and above the coal pillar, and pressure relief effect is the most obvious when fracturing borehole is located at goaf side of upper section working face. The hydraulic fracturing parameters determined by numerical simulation results were tested in field, the results show that after hydraulic fracturing is used for pressure relief, deformation stability period of surrounding rock of reused coal pillar roadway is 33.3% shorter than that of non-fractured roadway, and displacement of roof and floor and two side walls of reused coal pillar roadway is 63.5% and 45.5% lower than that of non-fractured roadway, which indicates deformation of surrounding rock of reused coal pillar roadway decreased significantly.