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基于隧洞开挖过程中围岩应力的实际调整路径设计加轴压卸围压条件下的分级卸荷流变实验,对某水电站引水隧洞洞轴线主要穿越的砂质泥岩的卸荷流变力学特性进行研究。试验结果表明:1应力水平低于岩石破坏应力时,砂质泥岩的流变只表现出衰减流变阶段和稳态流变阶段,且随着围压的逐级卸除,应力水平逐渐超过岩石的长期强度,试样的稳态流变速率由最初接近于0的常数逐渐增大至一个大于0的常数;2应力水平高于岩石破坏应力时,砂质泥岩经过衰减流变阶段和稳态流变阶段之后进入非线性加速流变阶段直至发生破坏,通过对比发现,不同卸荷初始围压下试样发生流变破坏的总历时不同,且各试样发生非线性加速流变的启动时间也显著不同。对砂质泥岩卸荷流变试验结果分析表明,西元模型能够较好地描述应力水平低于破坏应力时砂质泥岩的流变特性,但却无法反映应力水平高于其破坏应力时的非线性加速流变特征,基于此,引入岩石非线性加速流变启动元件,通过将其与西元模型相结合建立了一个新的非线性黏弹塑性流变模型,对提出的模型进行参数辨识,并将流变模型拟合结果与试验结果进行对比,结果表明,新建立的卸荷流变本构模型能够较全面地描述砂质泥岩卸荷流变破坏的全过程,证明所建模型是正确合理的。
Based on the actual adjustment path design of surrounding rock stress in tunnel excavation, the grading unloading rheological experiment under axial compression and unloading confining pressure was carried out to study the unloading rheological mechanical properties of sandy mudstone mainly crossing the tunnel tunnel axis of a hydropower station research. The results show that: 1, when the stress level is lower than the rock failure stress, the rheology of sandy mudstone shows only the decay rheological stage and the steady-state rheological stage. With the gradual removal of confining pressure, the stress level gradually exceeds that of rock The steady-state rheological rate of the sample gradually increases from a constant close to 0 to a constant larger than 0. When the stress level is higher than the rock failure stress, the sandy mudstone passes through the decay rheological stage and the steady state After the rheological stage, it enters the stage of nonlinear accelerating rheological deformation until it destroys. By comparison, it is found that the total duration of rheological failure of specimens under different initial unloading confining pressure is different, and the starting time of nonlinear accelerated rheological Also significantly different. The results of creep tests on sandy mudstone show that the model can describe the rheological properties of sandy mudstone well under the stress level lower than the failure stress, but it can not reflect the nonlinearity when the stress level is higher than the destructive stress Based on this, a new nonlinear viscoelasto-plastic rheological model was established by combining rock-nonlinear accelerating rheological start-up element with the Western model, and the parameters of the proposed model were identified. The results of the rheological model fitting and the experimental results show that the newly established unloading rheological constitutive model can describe the whole process of unloading creep damage of sandy mudstone in a comprehensive way and prove that the model is correct and reasonable .