基于钻孔卸压的硬脆性紫砂岩岩爆局部解危试验研究

Experimental Study on Local Risk Reduction of Rockburst in Hard Brittle Purple Sandstone Based on Borehole Pressure Relief

岩爆可造成严重的人员伤亡和经济损失,钻孔卸压是一种防治岩爆灾害的有效手段。基于声发射与数字图像相关技术(Digital image correlation method,DIC)对完整及不同夹角双钻孔紫砂岩进行单轴压缩岩爆试验,分析紫砂岩力学特性及破裂特征,得出声发射特征规律,并对钻孔卸压效果进行评估。结果表明:岩石表现出显著的脆性,起裂位置及破坏模式随夹角变化而变化;可将岩石的声发射时序变化特征划分为平静-突变型、缓增-数级突变型及稳增-突变型,在临近破坏阶段,以中幅值信号为主,并伴有一些高幅值信号;声发射b值总体上经历了先升后降的演化过程,有钻孔时的整体b值要比无钻孔时大,夹角为45°时的演化最值及整体数值都比较大,微裂纹发展更为充分;随着夹角的增大,卸压效果先增强再减弱,在30°~45°范围时最佳,90°时最差,当岩桥的破裂贯通与试样的整体剪切破坏方向一致时效果最好。研究结果可为卸压孔的布置优化提供理论参考。

Rockburst can cause serious casualties and economic losses.Borehole pressure relief is an effective means to prevent rockburst disaster.Based on acoustic emission and digital image correlation method(DIC),uniaxial compression tests of rockburst were carried out on intact specimens and double-hole specimens with different included angles.The mechanical properties and fracture characteristics of purple sandstone were analyzed,the acoustic emission characteristics were obtained,and the effect of borehole pressure relief was evaluated.The results show that the rock exhibits significant brittleness,and the initiation position and failure mode change with the variation of the angle change.The time series variation characteristics of acoustic emission of rock can be divided into three categories,including calm change-sudden change,slow increase-several sudden change and stable increase-sudden change.In the near failure stage,the medium amplitude signals are the mainstay,accompanied by some high amplitude signals.The b value of AE generally experiences the evolution process of rising first and then falling.The overall b value with borehole is larger than that without borehole.The maximum value of evolution and the overall value at 45°are relatively large,and the development of microcracks is more sufficient.As the angle increases,the pressure relief effect is first enhanced and then weakened,the best effect is in the range of 30°-45°,and the worst effect presents at 90°.The best effect is achieved when the fracture penetration of rock bridge is consistent with the overall shear failure direction of the specimen.The research results can provide a theoretical reference for the layout optimization of pressure relief holes.