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