应变型岩爆静-动态成灾过程中能量转换机理的实验与模型研究

The static-dynamic conversion process of fractured rock is the key to reveal disaster-causing mechanism of rockburst. It is indicated by researches that failure characteristics of the rock are related to the transformation of its accumulated strain energy into dissipated energy and the allocation proportion of the released energy. Firstly, focusing on the static-dynamic conversion process of “splitting into plates-shearing into pieces-ejection of pieces” of the strain mode rock burst, true triaxial loading-unloading failure tests and particle flow numerical simulation were conducted to investigate threshold limit values of the energy accumulation and release as well as the response mechanism between them and the evolution of meso-cracks, and explain the internal relation of the unloading path and failure characteristic. Secondly, particle flow numerical simulation was utilized to study stress path of conversion from static failure during unloading to dynamic failure of rock burst as well as kinetic energy criterion of dynamic failure of rock burst, based on which realize the indoor tests reflecting main features of rock burst, reproduce dynamic process of “ejecting out” of fractured rock, and obtain the rules of energy evolution during static-dynamic conversion. Finally, based on the work above, the state equation of energy accumulation of rock is proposed combining the generalized plastic mechanics theory, and through introducing the equation of motion for particle to depict the motion field of fractured rock and with help of the pulse theory, the energy model of disaster formation process of strain mode rock burst is determined, and the signs and conditions of the occurrence of rock burst are presented, which are validated with the rock burst instance in Jingping Project. Results of the project are of important theoretical and engineering values to the further recognition, prevention and treatment of rock burst.

破碎岩体由静态向动态转化的过程是揭示岩爆致灾机理的关键，研究表明岩体的破坏特征与其积聚应变能转变为耗散能和释放能的分配比例有关。围绕应变型岩爆“劈裂成板-剪断成块-块片弹射”的静、动转换过程，开展真三轴加卸荷破坏实验和颗粒流数值仿真，探索能量积聚、释放的临界阈值及其与细观裂纹演化间的响应机制，阐释卸荷路径与破坏特征间的内在关联。采用颗粒流数值仿真探索卸荷静力破坏转变为岩爆动力破坏的应力路径，探寻岩爆动力破坏的动能判据，据此实现体现岩爆主要特征的室内实验，再现破碎岩体“弹射飞出”的动态过程，获得静态到动态转换的能量演化规律。在此基础上结合广义塑性力学理论，给出岩体能量积聚状态方程，引入质点运动方程描述破碎岩体的运动场，利用冲量理论确定应变型岩爆成灾过程能量模型，提出岩爆发生的征兆及条件，结合锦屏工程岩爆实例验证。项目成果对进一步认识、预防与治理岩爆具有重要的理论与工程意义。

岩体破坏特征与其积聚应变能转变为耗散能和释放能的分配比例有关。围绕应变型岩爆“劈裂成板-剪断成块-块片弹射”的静、动转换过程，开展真三轴加卸荷破坏实验和颗粒流数值仿真，探索能量积聚、释放的临界阈值及其与细观裂纹演化间的响应机制。真三轴加、卸载应力路径下，花岗岩的破坏方式均为张剪复合破坏，表现出高损伤应力特征和明显的脆性特征；利用体积应变曲线提出新的脆性指数评价岩石脆性，发现卸载条件下花岗岩的脆性更高；真三轴加载试验中，总能量-轴向应变曲线经历缓慢增大、快速增大、稳定增大三个阶段；真三轴卸载试验中，在卸荷瞬间耗散能迅速增加，在能量分配中所占的比例迅速提高，成为消耗能量的主体；加荷试验中花岗岩试样破坏时的耗散能量值明显大于卸荷试验，表明加荷路径下需要消耗更多的能量才能发生破坏，且卸荷路径下可释放弹性应变能多，相较于加荷路径更加危险。花岗岩在真三轴加、卸载路径下均呈现张剪复合破坏特征；加载与卸载两种路径下弹性能先增大后减小，弹性能快速释放导致岩样发生宏观破坏，卸载路径下岩样破坏时各能量变化幅度更大。花岗岩变形过程的PFC3D模拟表明，粘结能是能量消耗主体，并导致颗粒间的粘结发生剪切断裂；岩样内部的张拉裂纹数远高于剪切裂纹数，表明花岗岩破坏以张拉破坏为主、剪切破坏为辅；卸载破坏中裂纹扩展速度在卸载后开始加速，极短时间内裂纹就会扩展贯通并发生破坏，表明卸载应力路径下花岗岩损伤积累时间更短，破坏速度更快。项目成果对进一步认识、预防与治理岩爆具有重要的理论与工程意义。