热弹塑性土体本构模型及在多场耦合数值模拟中的应用

A Thermo-elastoplastic Constitutive Model for Soil and Its Application in Multiply Phase Coupling Numerical Simulation

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 ＂thermal equivalent stress＂, a new thermo-elastoplastic consti- tutive model, which is different from the traditional concept of plasticity that the plastic strain occurs below the normally yield surface, was proposed. In the model, the degree of saturation and skeleton stress were used as independent state variables that could describe the saturated and unsaturated soil behavior in a unified way. In addition, the concepts of sub-loading and super- loading were also adopted that the overconsolidation and structure behavior of soil can also be de- scribed. The proposed model could simulate the mechanical performance of saturated/unsaturat- ed soil at different temperature condition in consolidation tests and triaxial shear tests quite well. Meanwhile, the model was incorporated into soil-water-air-thermal multi-phase coupling field theory and a heating test in deep soft rock layer was simulated by FE-FD method. The agreement between the results of heating test and simulation confirmed the property of the proposed thermo- elastoplastic constitutive model and numerical method. Thus, it could also be used in the analysis of energy piles and surround soils in the geothermal heat exchange system.