摘要:
煤柱上部应力是留巷巷道强烈变形的力源，对于变形严重的留巷巷道围岩控制，采用传统爆破卸压技术存在安全风险较高、污染环境、围岩破坏严重等问题。针对上述问题，提出了留巷巷道定向水力压裂卸压机理，即通过水力裂缝的扩展在顶板岩层中产生弱结构面，降低顶板岩石的整体强度，在采动应力作用下，使弱化后的坚硬顶板及时破断垮落，降低留巷巷道应力水平。以山西晋城无烟煤矿业集团有限责任公司长平煤矿4312综采工作面为试验地点，确定了定向水力压裂钻孔方案及钻孔布置参数。压裂结果显示：横向切槽深度达5 mm，切槽效果良好；进行分段逐次压裂时，随着压裂处距钻孔孔口距离的增加，裂缝扩展所需压力相应增大。对留巷巷道压裂段和未压裂段进行了表面位移、煤柱应力监测，监测结果表明：留巷巷道变形主要以两帮变形为主，压裂段两帮和顶底板平均移近量比未压裂时分别降低约40.79%和69.80%；未压裂段的煤柱应力在接近工作面时出现峰值点，而压裂段的煤柱应力在距离工作面切眼后方200 m左右出现峰值点，定向水力压裂转移了煤柱上部应力峰值位置。
Abstract:
Stress of upper coal pillar is the force source of strong deformation of retaining roadway. For surrounding rock control of retaining roadway with serious deformation, traditional blasting pressure relief technology has some problems such as high safety risk, environment pollution and serious surrounding rock damage. Aiming at the above problems, pressure relief mechanism of directional hydraulic fracturing in retaining roadway was proposed, that is, through expansion of hydraulic fracture, weak structural surface is generated in roof rock, overall strength of the roof rock is reduced, and the weakened hard roof is timely broken and caved under action of mining stress, so as to reduce stress level of retaining roadway. Taking 4312 fully mechanized coal mining face of Changping Coal Mine of Shanxi Jincheng Anthracite Mining Group Co., Ltd. as test site, boreholes scheme and boreholes layout parameters of directional hydraulic fracturing were determined. The fracturing results show that transverse grooving depth is 5 mm and grooving effect is good. During fracturing step by step, pressure required for fracture expansion increases with increase of distance between fracturing site and borehole. Surface displacement and coal pillar stress of fractured and non-fractured sections of retaining roadway were monitored. The monitoring results show that deformation of retaining roadway is mainly caused by two side walls deformation, and the average displacements of two side walls and roof and floor of the fractured section are about 40.79% and 69.80% lower than those of the non-fractured section. Stress of coal pillar in the non-fractured section appears peak point when approaching working face, while stress of coal pillar in the fractured section appears peak point at about 200 m away from back of cut hole of working face, which indicates that directional hydraulic fracturing transfers stress peak position of upper coal pillar.
百度学术
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