软岩热–弹–黏塑性本构模型

Thermo-elasto-viscoplastic model for soft rock

在诸多岩土工程如高放核废料处置、地热资源开发等应用中需要考虑软岩的长期力学特性,而温度升高会对软岩材料的蠕变破坏特性产生复杂影响,建立能反映蠕变破坏特性的本构模型具有理论价值和现实意义。从连续介质力学入手,基于下负荷面剑桥模型和等价应力的概念,建立了能描述软岩在温度作用下蠕变过程的热弹黏塑性模型。利用自主开发的仪器,采用大谷石进行了不同围压下的三轴蠕变试验,并对模型进行了验证。多种实验结果表明,材料在不同应力状态下,存在最优温度使得蠕变破坏最慢,此外,受温升影响时存在蠕变破坏加快和减慢两种现象,提出的模型能统一描述这两种现象。分析了模型特性,总结了不同材料参数和应力状态对蠕变规律的影响。

In the construction of many geotechnical projects, such as nuclear waste disposal and geothermal extraction and storage, it is necessary to consider the long-term mechanical properties of soft rock. Furthermore, the evaluated temperature will cause a complicated influence on the creep damage behaviors of soft rock. In consequence, it is theoretically and practically meaningful to establish a constitutive model which can describe the creep damage behaviors. Within the framework of continuum mechanics, a thermo-visco-elastoplastic model is proposed based on the sub-loading Cam-clay model and the concept of equivalent stress. Triaxial creep tests on Tage stone under different confining pressures are conducted by using the self-developed apparatus. Compared with the numerical results, the experimental results exhibit that for a certain stress state, an optimum temperature exists, which will slow down the creep damage rate the most. In addition, both retarding and accelerating effects on creep rapture due to limited warming are observed for the same material, and this phenomenon can be predicted by the proposed model. Finally, model characteristics are analyzed, and the influence of material parameters on creep laws is discussed.