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采用热等效应力的概念,提出一种新的热弹塑性饱和/非饱和土本构模型,其在正常屈服面以内仍然会发生塑性应变。该模型通过以饱和度和土骨架应力为状态变量,能够统一描述饱和、非饱和土体的热力学特性;还采用上下负荷面概念,考虑了土的结构和超固结发展特性。所提出的本构模型可以很好地展现饱和/非饱和土体在不同温度条件下固结压缩实验和三轴实验中的压缩和应力应变特性。将该模型导入土-水-气-热多场耦合有限元分析中,利用有限单元一有限差分法模拟了深层软岩加热高温试验。计算结果与试验结果吻合得很好,验证了所提出的本构模型与多相场耦合有限元方法的准确性,可尝试将其用于地热能开发与土体热力学特性的研究和模拟。
Based on the concept of thermo-equivalent stress, a new thermo-elasto-plastic constitutive model of saturated / unsaturated soil is proposed, in which the plastic strain still occurs within the normal yield plane. The model can describe the thermodynamic properties of saturated and unsaturated soils uniformly by taking saturation and soil frame stress as state variables. The concept of upper and lower load surfaces is also adopted to consider the characteristics of soil structure and overconsolidation. The proposed constitutive model can well show the compressive and stress-strain characteristics of saturated / unsaturated soils in consolidation and triaxial tests under different temperature conditions. The model was introduced into the soil-water-gas-heat multi-field coupling FEM and the finite element method was used to simulate the high-temperature heating of deep soft rock. The calculated results are in good agreement with the experimental results. The accuracy of the coupled finite element method and the proposed constitutive model is validated. It can be used for the research and simulation of geothermal energy development and soil thermodynamics.