考虑水致弱化及应变梯度的断层岩爆分析

ANALYSIS ON FAULT ROCKBURST CONSIDERING EFFECTS OF WATER WEAKENING AND STRAIN GRADIENT

研究了岩石含水量对断层-围岩系统稳定性及岩爆(冲击地压)对韧性断层变形的影响。含水量不仅影响岩石强度,也对应力-应变曲线应变软化阶段斜率有影响。基于梯度塑性理论和水致弱化函数,得到了剪切带内部的塑性剪切应变、总剪切应变及塑性剪切位移的分布规律。此外,还得到了不同含水量时剪力-塑性剪切位移的关系。研究结果表明:随着岩石含水量的增加,塑性剪应变降低,塑性剪切位移降低;含水量越大,则弹性阶段越短,耗散势能越小,外力功越小,断层岩爆释放的弹性能量也越小;岩石的含水量增加,则断层-围岩系统不容易发生失稳。

Stability analysis is made on the system composed of fault band and surrounding elastic rockmasses considering water weakening and strain gradient. The deformation of ductile fault after rock burst is investigated. It is found from experimental measurement that the shear strength and the absolute value of the slope of stress and strain curve are decreased with water content. Considering the deterioration of strength, the distribution rules of plastic shear strain and total plastic shear strain in shear band are proposed based on gradient-dependent plasticity. Besides, the relation between shear force and relative plastic shear displacement is also presented. The analytical result shows that the plastic shear strain and the plastic shear displacement decrease with water content. Larger water content leads to shorter elastic stage, lower dissipated potential energy and lower external force work. In addition, the released elastic strain energy increases as water content decreases. According to the analytical solution of axial stress-axial strain curve of rock specimen in uniaxial compression proposed by authors and experimental results, water content affects the softening modulus. The post-peak slope of shear stress and shear displacement curve of the system is presented considering the influence of water content on the softening modulus. It is shown that increment of water content reduces the possibility of instability.