大直径钻孔卸压机理室内及数值试验研究

钻孔卸压能够有效降低巷道上方及其周围岩体弹性能量的积聚,降低区域冲击危险性。因此,对大直径钻孔卸压机理及其合理参数的深入研究具有工程应用价值。通过室内试验研究孔径、孔间距及孔深等参数对试样强度的影响,以及分析不同参数影响下试样破坏形态;同时借助颗粒流PFC研究不同参数条件下试样裂纹扩展形态及裂纹数量。研究表明:裂纹扩展贯通导致的应力释放是钻孔产生卸压作用的根本原因,且孔径、孔深越大,钻孔周围裂纹数量越多,主控裂纹纹路越清晰,钻孔卸压效果越好;同样随着孔间距越小,试样破坏形态由独立型破坏转变为贯通型破坏,试样破坏强度明显降低,卸压效果明显。

Laboratory and numerical experiments on pressure relief mechanism of large-diameter boreholes

The technology of borehole pressure relief is an effective way to reduce the elastic energy accumulation in the surrounding rock of roadways, which can reduce the risk of regional rock bursts. Therefore, the studies on the pressure relief mechanism of large-diameter boreholes and the corresponding reasonable parameters are of high engineering application value. A series of laboratory experiments are conducted to analyze the effects of different parameters such as borehole radius, spacing and depth on the uni-axial compression strength (UCS) and failure patterns of samples. The particle flow code (PFC) is used to quantify the micro-cracks and simulate their corresponding propagation process. The laboratory and numerical results show that the stress release resulting from propagation and coalescence of micro-cracks is the basic reason for the pressure relief around the surrounding rock of boreholes. The micro-cracks around the surrounding rock increase with the increase of radius and depth of boreholes, and the main crack becomes much more serious, resulting in larger pressure relief. In addition, as the borehole spacing decreases, UCS of samples decreases and the corresponding failure pattern changes from independent one to transfixing one, leading to a much more obvious pressure relief effect.