开挖卸荷诱导的高储能岩体能量动态释放过程研究

Study on energy release process of high energy storage rock mass induced by excavation unloading

针对深部岩体开挖,在确定围岩储能极限的基础上,采用优化的局部能量释放率和释放系数指标,研究开挖瞬态卸荷诱导的高储能岩体能量动态释放过程,并分析能量释放与围岩损伤之间的关系。研究结果表明:在开挖卸荷作用下,围岩应变能经历先减小后增大再减小最终稳定的动态变化过程,第一次先减小后增大的动态波动过程与弹性条件相似,由弹性卸载应力波引起,不会造成围岩损伤破坏,而第二次减小由围岩聚集应变能超过其储能极限造成,必然会引起围岩损伤破坏;围岩能量释放率随与开挖面距离的增大先缓慢增大后快速减小,并且越靠近开挖面,能量释放系数越大,完成能量释放所需的时间越短,能量释放越剧烈;此外,能量释放率和释放系数越大,围岩波速降越大,围岩损伤破坏越严重。因此,可通过计算围岩能量释放系数,实现对围岩损伤破坏程度的评估和预测。

For the case of excavation of deep rock mass,based on the determination of energy storage limit,the energy release process of high energy storage rock mass induced by transient unloading of in-situ stress was studied by using local energy release rate and energy release coefficient indexes,and the relationship between energy release and damage of surrounding rock mass was analysed. The results show that,influenced by the excavation unloading,the strain energy of surrounding rock mass firstly decreases,then increases,soon reduces and stabilizes at last. Similar with the elastic case,the first decrease process of strain energy is mainly caused by elastic unloading wave and does not induce damage in surrounding rock mass. While the second decrease process is mainly caused by that the strain energy accumulated in the surrounding rock mass exceeds the energy storage limit,and is bound to induce damage in surrounding rock mass. Further study shows that with the increase of the distance from the excavation face,the energy release rate of surrounding rock increases first and then decreases. The closer distance from excavation boundary means the larger energy release coefficient,the shorter duration time of energy release,and the more drastic energy release. In addition,the bigger energy release rate and coefficient means the larger wave velocity drop and the more serious damage in surrounding rock mass. Therefore,damage degree of surrounding rock mass can be assessed and predicted by calculating the energy release coefficient.