圆形巷道围岩加速蠕变影响下冲击地压的启动条件

Rockburst start-up condition influenced by accelerated creep of surrounding rock of circular roadway

针对高静载巷道蠕变型冲击地压现象,研究弹性区煤岩加速蠕变对巷道冲击的影响。基于等时应力应变曲线与全应力应变曲线的关系,得到了煤岩加速蠕变破坏的时效力学参数。通过分析巷道弹性区煤岩加速蠕变过程及其条件,并考虑围岩塑性区强度的应变软化,推导出圆形巷道围岩蠕变塑性区应力场。在此基础上,借鉴冲击地压扰动响应判别准则理论的思想,探讨了巷道围岩加速蠕变影响下的冲击启动机制,给出了冲击启动临界条件的解析解,分析了支护力和等时应力-应变曲线的割线模量比Mt对冲击临界条件的影响。结果表明:高地应力、初次支护的低支护力和煤的低单轴长期强度为巷道弹性区煤岩产生加速蠕变提供了有利条件,加速蠕变导致冲击启动通过弹性区煤岩强度的时效劣化实现;巷道所处地应力越高,弹性区煤岩只需历经较小的强度劣化,就可冲击启动;加速蠕变影响下,增大支护力对抑制冲击发生有促进作用,表现在支护力越高,弹性区煤岩需历经较大的强度劣化才可冲击启动,且启动时围岩内峰值应力较低、塑性区阻抗较大;煤岩单轴压缩峰后与峰前模量比(λ/E0)是巷道弹性区煤岩产生加速蠕变的非影响因素,但其是巷道冲击启动的重要影响因素,即巷道弹性区煤岩产生加速蠕变的临界地应力判据与模量比无关,模量比越小弹性区煤岩需历经更大程度的强度劣化才可冲击启动;抑制巷道蠕变冲击的核心在于控制弹性区煤岩不满足产生加速蠕变的条件。

Aiming at the creep rockburst phenomenon of roadway with high static load,the effect of accelerated creep of coal-rock in elastic zone on roadway rockburst was studied.Firstly,based on the relationship between the isochronous stress-strain curve and the complete stress-strain curve,the time-dependent mechanical parameters of accelerated creep damage of coal-rock were obtained.Then,by analyzing the accelerated creep process and its conditions of coal-rock in elastic zone of roadway,and considering post-peak strength softening of the plastic zone,the stress field of plastic zone of the circular tunnel was derived.Based on this,combining with the idea of the criterion of disturbance response,rockburst start-up mechanism and its critical condition influenced by accelerated creep of surrounding rock were discussed.Finally,the effect of the support force and the secant modulus ratio Mt of the isochronous stress-strain curve were analyzed.The results show that high ground stress,low support force of the primary support and low uniaxial long-term strength of the coal provide favorable conditions for emerging accelerated creep of coal-rock in the elastic zone of roadway.Meanwhile,rockburst start-up is formed through the time-dependent strength deterioration caused by accelerated creep of coal-rock in elastic zone.With the higher ground stress of roadway,rockburst start-up can be activated only undergoing small strength deterioration of coal-rock in the elastic zone.In addition,under the influence of accelerated creep,increasing the supporting force can promote to inhibit occurring of rockburst.It means that coal-rock in the elastic zone needs to undergo larger strength deterioration for rockburst start-up with the higher supporting force.Moreover,the peak stress in surrounding rock is lower and the resistance in the plastic zone is larger under this circumstance.Besides,post-peak and pre-peak modulus ratioλ/E0 of coal-rock under uniaxial compression is the non-influencing factor of accelerated creep of coal-rock in the elastic zone of roadway,but it is an important influencing factor for rockburst start-up of the roadway.Namely,the critical ground stress criterion of emerging accelerated creep of coal-rock in the elastic zone is independent ofλ/E0 and coal-rock in the elastic zone needs to undergo a greater degree of strength deterioration for rockburst start-up with the smaller value ofλ/E0.Moreover,the core for inhibiting creep rockburst of roadway lies in controlling the elastic zone coal-rock not to reach the condition of emerging accelerated creep.