大理岩结构面非线性蠕变损伤本构模型研究

针对锦屏二级水电站地下洞室群围岩富含节理的情况,对主要围岩大理岩进行含软弱夹层的剪切蠕变试验,结果表明在应力水平较低时,蠕变变形主要有瞬时弹性变形和黏弹性变形组成,当应力水平较高时,蠕变变形主要有瞬时弹性变形,黏弹性变形和黏塑性变形组成。在广义开尔文模型基础上增加一非线性项,来描述衰减蠕变阶段和稳定蠕变阶段;根据加速蠕变阶段岩石的损伤特性,选取基于应力水平和时间因素的损伤变量,建立了岩石非线性蠕变损伤本构模型,并通过试验结果对该模型进行参数辨识,验证了该模型的正确性和合理性。然后,分别利用该模型和西原(Nishiharamodel)模型对加速蠕变阶段进行拟合,结果表明提出的模型能很好地描述加速蠕变阶段,克服了西原模型的不足。

STUDY OF NONLINEAR CREEP DAMAGE MODEL OF MARBLE WITH STRUCTURAL PLANE

The surrounding rock masses of Jinping Second Stage Hydropower Station caves have abundant joints. A shear creep test was carried out on the marble weak interlayer. The results show that, the creep deformation is mainly consists of the instantaneous elastic and viscoelastic deformation when stress level is low; when stress level is high, creep deformation is mainly composed of the instantaneous elastic, viscoelastic strain and viscoplastic deformation. By increasing a nonlinear term based on generalized kelvin model, the attenuation creep phase and the stable creep stage can be described. According to damage characteristics of rock in the accelerated creep stage, a nonlinear creep damage constitutive model of rock was established by choosing a damage variable based on stress level and time. The parameters of the model were identified by the experimental results, which demonstrates the correctness and rationality of the model. Then, by using the creep damage model and Nishihara model respectively to fit the experiment data of accelerating creep stage, results show that the creep damage model can describe accelerated creep stage very well and overcome the shortage of Nishihara model.