强岩爆倾向性岩石的自组织动力失稳机制

Self-organizing dynamic instability mechanism of rocks with high rockburst proneness

为探究岩石的动力失稳机制,开展强岩爆倾向性岩石的单轴声发射试验,分析其应力-应变、声发射演化及宏细观破坏特征,结果表明岩石的动力失稳是其微结构系统逐渐形成一定几何形状的力学结构,继而力学结构突然崩溃的自组织行为,具有临界性、对称性破缺及塑性缺失等性质。将岩石的动力失稳过程划分为能量积蓄和能量爆发2个阶段,依据自组织的自催化-自阻化功能,考虑对称性破缺,分别建立能量积蓄和能量爆发的非线性动力学方程,并推导出相应的耗散能演化方程。引入二元介质理论,将岩石的破损视为弹脆性胶结元向弹塑性摩擦元转化,摩擦元满足莫尔-库仑(M-C)准则,依据能量积蓄过程的耗散能演化方程定义破损规律,建立岩石的二元介质模型,依据能量爆发阶段的耗散能演化方程定义损伤规律,建立岩石的损伤模型,实现所建模型在有限差分软件中的二次开发,并验证了其正确性。基于自组织理论,结合数值模拟,从能量角度和细观层面分析岩石的动力失稳机制,结果表明:理想均质岩石的微结构系统可在势能梯度作用下演化成“沙漏”形的中心对称力学结构,临界态时势能梯度面密集靠近对称中心的岩桥,且能量可在面内高速流动,岩桥极易破断,破断后可打破周边密集的势能梯度面,引发面内能量激烈释放,驱动岩石爆裂;真实岩石失稳过程中会产生对称性破缺的力学结构和破坏形态。研究成果可为岩柱、硐室围岩的岩爆危险性分析提供理论支撑和数值模拟手段。

In order to explore the dynamic instability mechanism of rocks,uniaxial acoustic emission tests on rocks with high rockburst proneness were carried out.The stress-strain,acoustic emission evolution,macro and meso failure characteristics were analyzed.The results indicate that the dynamic instability of rocks is a self-organizing behavior of their meso-structural systems gradually forming a certain shape of mechanical structure,and then the mechanical structure suddenly collapses,which has the properties of self-organized criticality,symmetry breaking and loss of plasticity.The dynamic instability process of rocks was divided into two stages:energy accumulation and energy explosion.Based on the self-catalysis self-inhibition mechanism of self-organizing systems,the nonlinear dynamic equations for energy accumulation and energy explosion considering symmetry breaking were established respectively,and the corresponding dissipative energy evolution equations were derived.The binary medium theory was introduced and the breakage of rocks was regarded as the transformation of elastic-brittle cementation elements to elastic-plastic friction elements.The friction elements follow the Mohr-Coulomb criterion.The breakage law was defined according to the dissipative energy evolution equation of the energy accumulation stage.A binary medium model for rocks was established.The damage law was defined according to the dissipative energy evolution equation of the energy explosion stage and a damage model for rocks was established.The mechanical models were embedded in the finite difference software and were verified as correct.Based on the self-organization theory and combined with the numerical simulation results,the dynamic instability mechanism of rocks was analyzed from the perspective of energy and meso-scopic level.The results show that the meso-structural systems of ideal homogeneous rocks can evolve intoa centrally symmetric mechanical structure in the shape of hourglass under the influence of potential energy gradients.At the critical state,the potential energy gradient surfaces are densely gathered toward the center of the mechanical structure and the energy can flow at high speed within the surface.The rock bridge located at the symmetrical center can be easily torn apart,which can break the potential energy gradient surfaces around it and trigger a intense release of the in-plane energy and rock burst.The mechanical structure and failure mode with symmetry breaking will occur during the instability process of real rocks.The research results can provide theoretical support and numerical simulation means for the dynamic instability analysis of rock pillars and tunnel surrounding rock.