高应力状态下岩石蠕变本构模型的研究

Study on the Constitutive Model of Rock Creep under High Stress State

为探究高应力状态下岩石蠕变损伤本构的问题,开展不同应力水平蠕变试验。通过理论分析提出了一种新的损伤表达式,利用其修正了蠕变参数,建立了一种考虑损伤全过程的蠕变本构模型,并结合试验结果分析了模型参数规律。结果表明:高应力状态下,随着应力的增大,岩石在单调加载过程中引起的初始损伤分别为0.21、0.31和0.4,对应蠕变寿命,其随着蠕变应力水平的增大而减小;新模型能够较好地反映蠕变应变三阶段特征,尤其是在稳态段应变的增长趋势与试验结果更为一致,相关性系数均≥0.98;蠕变段弹性模量与黏弹性系数均随着应力比的增大呈现先快后慢的非线性减小趋势。

In order to investigate the constitutive problem of rock creep damage under high stress conditions,creep tests at different stress levels are conducted.A new damage expression is proposed through theoretical analysis,and the creep parameters are corrected.A creep constitutive model considering the damage process is established,and the parameter rules of the model are analyzed according to the experimental results.The results show that under high stress conditions,with the increase of stress,the initial damage caused by rock during monotone loading is 0.21,0.31 and 0.4,respectively,corresponding to creep life,which decreases with the increase of the creep stress level.The new model can reflect the three-stage characteristics of creep strain better,especially in the steady-state strain growth trend,which is more consistent with the test results,with the correlation coefficients not less than 0.98.The elastic modulus and viscoelastic coefficient of the creep section both show a nonlinear decreasing trend of first increasing and then decreasing slowly with the increase of stress ratio.