基于剪切应变梯度塑性理论的断层岩爆失稳判据

INSTABILITY CRITERION OF FAULT ROCKBURST BASED ON GRADIENT-DEPENDENT PLASTICITY

应用应变梯度塑性理论及能量准则,提出了断层岩爆的失稳判据的解析解。断层带被视为一维剪切问题,断层带尺寸由岩石内部长度确定。断层带的一半及带外一侧的弹性岩石被视为一个系统。得到了依赖于断层带尺寸的断层带的耗散势能及峰后刚度表达式。应用能量准则,得到了断层带-围岩系统的失稳判据,它不仅与岩石材料的本构参数有关,也与岩石结构的几何尺寸有关,说明系统的稳定性具有尺寸效应。断层岩爆失稳判据与矿柱岩爆失稳判据具有类似性。目前的断层岩爆失稳判据的优越性在于:断层带的宽度、断层带的耗散势能、峰后刚度及失稳判据等都可以解析表示;而且,断层带内部具有不均匀的(塑性)剪切应变,这一点与有关的实际观测结果相符合。

Analytical solution of instability criterion for fault rockburst is proposed using shear strain gradient plasticity theory and energy criterion. Fault band is treated as one dimensional shear problem and the thickness of the band is dependent on characteristic length of rock. Dissipated potential energy and post-peak stiffness of fault band are deduced and both of them are concerned with the thickness of fault band. To propose an instability criterion,half of fault band and half of elastic rock outside the band comprise a system to which energy criterion is applied. The criterion shows that stability of the system depends on the constitutive parameters and structural size. So,the criterion exhibits size effect. Present instability criterion for fault rockburst is analogous to coal pillar rockburst criterion,for lower ratio of shear elastic modulus to shear softening modulus and lower ratio of thickness of fault band to size of elastic rock outside fault band lead to instability of the system. The advantages of present investigation for fault rockburst based on gradient-dependent plasticity are that thickness of fault band,dissipated potential energy,post-peak stiffness and instability criterion can be analytically presented,and plastic shear strain is localized into fault band,which is consistent with field observations.