Influence of hydraulic fracturing parameters of reused coal pillar roadway on pressure relief effect
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摘要: 针对煤柱留巷围岩变形控制采用的水力压裂卸压技术，为确定水力压裂参数，以山西晋城无烟煤矿业集团有限责任公司长平煤矿43122煤柱留巷为研究对象，利用平面离散元UDEC软件对水力压裂钻孔压裂次数和压裂位置对卸压效果的影响进行了数值模拟。结果表明：压裂分段长度越大，相应压裂次数越少，水力压裂对顶板的弱化效果越差，压裂分段长度以不超过4 m为宜；压裂钻孔位于下区段工作面煤柱侧时会引起煤柱应力升高，压裂钻孔位于上区段工作面采空区侧和煤柱上方时均能实现煤柱应力降低，其中压裂钻孔位于上区段工作面采空区侧时卸压效果最明显。根据数值模拟结果确定的水力压裂参数进行了现场试验，结果表明，采用水力压裂卸压后，煤柱留巷围岩变形稳定期较未压裂时缩短33.3%，煤柱留巷顶底板移近量和两帮移近量较未压裂时分别降低63.5%和45.5%，煤柱留巷围岩变形量显著减小。Abstract: 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.
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