考虑刚度劣化的剪切带-围岩系统稳定性分析

峰后的刚度劣化现象（渐进损伤）在多种煤、岩石、混凝土、土和砂子的循环加载实验中已被观察到。本文考虑了剪切带及带外弹性体的不同的刚度劣化现象，推导了剪切带（断层）-弹性围岩系统在直剪条件下的应力-变形曲线。剪切带的刚度劣化不改变剪切带的总变形，但使剪切带的弹性变形增加、塑性变形降低。考虑弹性体的刚度劣化现象之后，系统的峰后应力-变形曲线呈现非线性特征，这不同于过去忽略刚度劣化现象的结果。在应变软化过程中，剪切带之外弹性体的刚度劣化，使系统的峰后响应由负斜率（Ⅰ类行为）变为正斜率（Ⅱ类变形行为）。较高的弹性体尺寸、较高的脆性、较小的内部长度、较低的围岩初始弹性模量、较高的抗剪强度、较低的残余剪切应力及较高的残余剪切弹性模量，使系统的峰后响应变得陡峭，甚至发生Ⅱ类行为，使系统的失稳（岩爆、冲击地压、采矿诱发地震或矿震）易于发生。

Stability Analysis of Shear-band and Surrounding-rock System Considering Stiffness Deterioration

The phenomenon of stiffness deterioration （progressive damage） beyond the peak stress has been observed in cyclic loading tests of coals, rocks, concretes, soils and sands. In this paper, different cases of degraded stiffness in a system of shear-band （or fault） and its outside elastic rock were taken into account to derive the post-peak stress-deformation curve of the system in the direct shear condition. When stiffness deterioration in the shear-band is considered, the total shear deformation of the shear-band does not change but the elastic deformation increases while the plastic deformation decreases. Stiffness deterioration in the elastic body leads to the nonlinear post-peak stress-deformation curve of the system, which is different from the previous result with stiffness deterioration neglected. In the process of strain-softening, the structural response of the system changes from Class Ⅰ to Class Ⅱ behavior, which is attributable to the stiffness deterioration in the elastic body. Larger the elastic body, higher the post-peak brittleness, short- er the internal length, softer the initial elastic modulus, more strong the shear strength, less the residual shear stress, and stiffer the residual shear modulus will all lead to steeper the post-peak structural response of the system, even result in the class Ⅱ behavior, and be liable to make the system losing the stability （rock bursts, bumps, mining induced earthquakes or mine tremors）.