开挖卸荷扰动下应变型岩爆的能量释放诱发机理研究

During the excavation of deep rock mass under the condition of high in-situ stress, rockburst often occurs as a disaster and threatens the construction safety. The energy release of surrounding rock mass caused by excavation unloading is one of the important inducements of rockburst, but the inducing mechanism is still unclear trapped by complexity of the actual unloading path and the confining pressure environment. For the excavation of deep rock mass, the mechanism of rockburst induced by energy release under the disturbance of excavation unloading will be studied in this project by the method combining theoretical analysis, numerical simulation and field test verification. By analyzing and simulating the fracture process of rock mass during the excavation of deep tunnel, a three-dimensional mechanical model will be established to describe the transient release of in-situ stress; According to the field monitoring of the surrounding rock stress, the unloading path and confining pressure will be determined, and the energy release process of surrounding rock mass will be studied. Furthermore, a rockburst criterion based on energy release rate considering the effect of confining pressure under the actual unloading path will be set up, and the mechanism of rockburst induced by energy release will be revealed. Finally, a prediction method of rockburst based on energy release rate will be established. The research results will be helpful to understanding the mechanism of rockburst induced by energy release, and can provide an effective means for the prediction of rockburst.

高地应力条件下深部岩体开挖过程常常会发生岩爆灾害现象，威胁施工安全。开挖卸荷引起的围岩能量释放是岩爆灾害重要诱因之一，但是鉴于实际卸荷路径及围压环境的复杂性，其诱发机理仍不清楚。本项目针对深部岩体开挖，拟采用理论分析、数值模拟、现场试验相结合的方法，研究开挖卸荷扰动下应变型岩爆的能量释放诱发机理。通过对深埋隧洞开挖岩体破碎过程的理论分析和数值模拟，建立瞬态卸荷三维力学描述模型，结合现场跟踪监测的围岩应力变化历程，验证并确定瞬态卸荷路径及围岩所处围压环境，研究瞬态卸荷诱导的围岩能量动态释放过程；建立真实卸荷路径下反映围压影响的岩爆能量释放速率判据，揭示能量释放诱发岩爆灾变机理，提出基于能量释放速率的岩爆预报方法。研究成果将有助于加深对深部岩体工程岩爆灾变机理的认识，为施工过程中的岩爆灾害预报提供有效手段。

西部大开发战略的进一步实施促使一大批大型水电工程正在或即将在我国西南地区密集建设。受西南峡谷地区地形条件限制，这些工程大多涉及高强度、大规模的地下洞室群开挖，埋深大和地应力高是该地区地下岩体开挖工程的典型特征。高地应力条件下深部岩体开挖过程中常常会发生应变型岩爆，容易造成施工人员伤亡及施工设备损坏，从而威胁地下洞室的施工安全。本项目针对深部岩体爆破开挖，围绕“开挖卸荷扰动下应变型岩爆的能量释放诱发机理”这一研究主题，首先确定了与爆破参数对应的地应力瞬态卸荷的开挖荷载幅值、卸荷起始时刻、卸荷持续时间、卸荷方式，建立了地应力瞬态卸荷数学描述模型；然后，求解了三角形爆破荷载、地应力瞬态线性卸载及二者耦合作用下围岩动应力场，揭示了深部岩体爆破开挖围岩应变能动态调整过程，并借助岩石储能极限和残余弹性能密度两个参数分析了瞬态卸荷作用下围岩能量动态释放过程；最后，量化了平均能量释放速率与岩爆等级之间的数学关系，建立了基于平均能量释放速率的岩爆预测模型。研究成果可为深部岩体工程岩爆灾害预报提供有效手段。