分级加载条件下的锯齿状结构面剪切松弛特性

Shear relaxation characteristic of serrate structure surface under stepwise loading

摘要:

为研究结构面的剪切应力松弛特性，采用水泥砂浆浇筑成不同角度的结构面试样，利用岩石双轴流变试验机对规则齿形结构面进行不同剪切应力水平下的松弛试验，试验结果表明：结构面剪切应力松弛曲线可以分为瞬时、减速和稳态3个阶段；依据松弛曲线特征，考虑模型参数的时间相关性，将粘滞系数看作是与时间有关的非定常参数，建立非线性Maxwell松弛方程，与试验曲线拟合结果比较理想，得到了初始粘滞系数与剪应力水平的关系；根据松弛应力随剪应力水平的变化规律，及蠕变确定长期强度的机理，提出了应力松弛试验确定长期强度的方法，即松弛应力峰值对应的剪应力为结构面的长期强度.

Abstract:

To investigate the relaxation characteristic of rock mass discontinuity with different slope ratios and normal stresses, the stress relaxation tests of dentate discontinuity poured by cement mortar on the condition of shear stress were carried out by using biaxial creep machine. The test results show that: the relaxation curves can be divided into three stages, i.e. the instantaneous relaxation stage, attenuation relaxation stage and stable relaxation stage; the shear nonlinear Maxwell relaxation equation is obtained by constructing the relation between viscosity coefficient and time, the curves of the empirical equation agree with the test ones and get change law of initial viscosity coefficient and change rate with shear stress; according to change law of relaxation stress with shear stress and mechanism of determining long-term strength using transition creep law, a stress relaxation method is proposed to determine the long-term strength, which is relaxation stress peak method.