煤矿深部巷道软弱围岩密集钻孔卸压技术与应用

Pressure relief technology using dense borehole in soft surrounding rock of deep coalmine roadway and its application

煤矿深部围岩高应力与低强度之间的矛盾是诱发巷道大变形破坏的主要原因。为探究煤矿深部软弱围岩钻孔卸压技术,分析深部岩体开挖引起的扰动应力场演化分区特征,揭示高应力软岩巷道钻孔卸压机制,研究卸压钻孔群的合理设计方法,提出平行布置、扇形布置和管棚式布置3种卸压钻孔排布方法,并对比分析各方法的优缺点。最后,选择在顾桥煤矿近千米深井软岩巷道进行了应用试验,在卸压试验段选用扇形布孔方式共施工96个卸压钻孔。巷道表面位移监测结果表明:与非卸压区临近相似地质条件巷道相比,卸压试验段围岩两帮变形量降低约35.71%,顶板下沉量降低约33.43%,底鼓量下降约35.84%。与非卸压区测点对比,巷道同侧12 m深度处的应力释放率约为18.5%。研究表明:合理的钻孔卸压方式能有效降低集中应力,利于巷道稳定控制和大变形灾害的防控,可作为深部高应力软弱围岩大变形灾害防控的辅助手段。

The contradiction between high stress and low strength in deep surrounding rock of coal mines is a key factor leading to large deformation and failure in deep roadways.In order to investigate borehole pressure relief technology in soft rock of deep roadways,the evolution characteristics of the disturbed stress field were analysed.Then,the mechanism of borehole pressure relief in soft rock under high stress is revealed,and the reasonable design method of borehole group is proposed.Three layout modes of pressure relief boreholes were proposed,including parallel layout,fan-layout and pipe-shed layout.The advantages and disadvantages of each layout modes were compared and analysed.Finally,an application experiment is carried out in a deep roadway with soft rock in Guqiao Coal Mine.A total of 96 pressure relief boreholes were drilled using the fan-shaped layout method.Surface displacement monitoring results indicated that,compared with the roadway near similar geological conditions in the non-depressurized area,the deformation of the surrounding rock in the depressurized section can be reduced by about 35.71%,the roof subsidence by approximately 33.43%,and the floor heave by approximately 35.84%.The stress release rate at 12 m depth inner the rock mass is approximately 18.5%.Our research demonstrates that reasonable drilling pressure relief can effectively reduce the concentrated stress,which is conducive to the stability control of roadway and the prevention and control of large deformation disasters.Pressure relief technology using dense borehole can be applied as an auxiliary means for the prevention and controlling large deformation disasters in deep,high-stress,weak surrounding rock.