针对煤柱留巷支护问题,提出一种控制坚硬厚顶板煤柱留巷变形的新方法——定向水力压裂留巷卸压技术,旨在转移护巷煤柱上的高采动应力,改善留巷的应力状态,并提出定向水力压裂煤柱留巷卸压机理。以余吾煤业公司S1206煤柱留巷瓦排巷为研究对象,确定了定向水力压裂钻孔方案、钻孔布置参数及施工工艺。压裂结果显示,横向切槽机械钻头可以在预定位置预制开槽;21~28 m分段压裂时间占总压裂时间48%,是整个钻孔的压裂关键位置;采用间接方法判断裂隙的扩展范围20 m左右。对压裂段和非压裂段进行了表面位移、煤柱垂直应力、工作面超前支承压力、压裂段煤柱上方三向应力等监测。监测结果表明:压裂段两帮收缩量降低30.5%,顶底板移近量降低50.2%;超前压力的影响距离不超过50 m,距离工作面超过15 m左右时,出现应力峰值;超前工作面10 m左右范围内出现塑性破坏;采动影响最显著的作用来自垂直应力;采空区造成应力扰动方向与最大相对主应力方向一致。监测与评估表明卸压效果明显。压裂及卸压结果表明,采用定向水力压裂留巷卸压技术可以消除或减弱坚硬顶板形成的悬顶效应,达到留巷的目的。

In order to solve the problem of reused coal pillar roadway support,a new method to control the deformation of coal pillar in hard thick roof is presented in this paper-pressure relief technology of directional hydraulic fracturing ( HF). The purpose is to transfer the high mining stress on the roadway pillars and improve the state of the reused coal pillar roadway. De-stressing mechanism by directional HF is presented. A case study was performed at the S1206 meth- ane roadway of the Yuwu Coal Mine. Determine the directional (HF) boreholes program,boreholes layout parameters and construction technology. It is found that directional slots can be successfully cut by using dedicated grooving bits. 21-28 m staged fracturing time 48% of the total time of fracturing,which are the key position of the entire drilling;the indirect method to determine the fracture extended range of about 20 m. Pillar stress,front abutment pressure and road- way convergence were monitored in different stations with and without HF treatment. Stress changes in three directions within the pillar where HF has been performed were also monitored. It is found that the wall-to-wall convergence and the roof-to-floor convergence were reduced 30. 5% and 50. 2% due to the HF treatment,respectively. Front abutment was detectable within 50 m ahead of the longwall face. The peak pressure occurred at a distance of 10 m out by the face. Failure extended out by the face for a distance of around 10 m. Vertical stress is a major contributor to the influ- ence of mining-induced stress. The direction of the induced-stress is consistent with the maximum principal stress. Mo- nitoring and evaluation showed that the pressure relief effect was obvious. It is demonstrated from the case study that the function of the used roadway can be preserved by using the directional HF technique.