锯齿形结构面剪切流变特性分析

Shear rheological characteristics of serrate structure surfaces

利用岩石双轴流变试验机,对水泥砂浆浇筑的不同角度的规则齿形结构面试件进行了剪切蠕变试验和松弛试验。试验结果表明:蠕变曲线与松弛曲线形态相似,都有衰减和稳定两个阶段,全过程曲线都呈阶梯状变化,松弛曲线为非完全应力衰减曲线;采用Burgers蠕变模型和松弛模型对蠕变曲线和松弛曲线进行拟合,吻合程度较好。除了参数G1外,蠕变模型的参数值比松弛模型的参数值大;在分析松弛速率与应力水平关系的基础上,提出了用分级加载松弛试验确定长期强度的方法,即:松弛速率拐点对应的剪应力为岩石的长期强度,此方法与稳态蠕变速率确定长期强度的机理一致,而且两种方法确定的长期强度值相同。

The creep and stress relaxation tests for the dentate discontinuity poured by cement mortar are carried out by using biaxial creep machine. According to the creep and stress relaxation test results,there are many similarities of the patterns between the creep curves and the relaxation curves. Both creep curves and relaxation curves of the samples could be divided into two stages： attenuation stage and stable stage.The complete curves of creep and relaxation are all stepwise change against time,and relaxation curves are incomplete stress attenuation. Burgers model is selected to fit the creep curves and relaxation curves,and the fitted curves agree well with the experimental data. The parameter values of creep model are larger than that of relaxation model except the values of G1.According to the change law of the relaxation rate with the stress level,a stress relaxation method is proposed to determine the long-term strength. The relaxation rate-stress curve has obvious inflection point namely to correspond to the long-term strength,and the mechanism of this method and the steady creep rate is the same. The values of long-term strength determined by two methods are the same.