含预应力锚杆煤岩组合体破坏及声发射特征试验研究

Experimental investigation on the failure and acoustic emission characteristics of coal-rock combination with prestressed bolt

为探究预应力锚杆对煤岩组合体的锚固效应,开展了4组不同界面倾角(15°、30°、45°、60°)含预应力锚杆与仅含锚杆组合体的单轴压缩室内模拟试验,从试样破坏形态、应力-应变曲线特征及声发射参数特征3方面探讨了含预应力锚杆组合体的力学响应。结果表明:含预应力锚杆组合体残余强度与峰值强度的比值更高,预应力的施加使峰值应力前组合体能量释放增加,有效抑制了峰后能量释放,减少了组合体发生滑移破坏时与锚杆接触面的损伤,同时降低了应力波动的发生频次。含预应力锚杆与仅含锚杆组合体低频高幅信号占比随荷载的施加均呈阶段性变化特征,在组合体发生滑移时,施加在锚杆中的预应力抑制了加载初期低频高幅信号的集中;在各界面倾角下,含预应力锚杆组合体低频高幅信号占比及其标准差均更低,表明预应力锚杆有效抑制了组合体峰前内部裂纹的萌生,且降低了组合体内部裂纹演化对界面倾角变化的敏感性。

In order to investigate the bolting effects of prestressed bolt on coal-rock combinations(CR),four sets of uniaxial compression tests were carried out on CR containing prestressed bolt(CRPB)and bolt(CRB)at different interface inclination angles(15°,30°,45°and 60°),and the mechanical responses of the CRPB and CRB were analyzed from failure mode,stress-strain curve and acoustic emission(AE)characteristics.The results show that the ratios of residual stress to peak stress for the CRPB are higher.Additionally,the application of prestress increases the energy release before the peak stress,and effectively inhibits the energy release after the peak.Moreover,the prestress also reduces the damage of the contact surface between the combination and the bolt when the sliding failure occurs,and weakens the stress fluctuation.The proportions of low-frequency and high-amplitude(LF-HA)AE signals of the CRPB and the CRB both increase first and then decrease with the application of load.However,the prestress inhibits the concentration of LF-HA AE signals when the slide occurs at interface between coal and rock.Moreover,under different interface inclination angles,the proportion of LF-HA AE signals of the CRPB and the corresponding standard deviation are lower,indicating that the prestressed bolt effectively inhibits the initiation of microcracks before the peak of the combination and reduces the sensitivity of the microcracks evolution to the variation of interface inclination angle.