基于下加载面概念的饱和黏土温度–应力耦合弹塑性模型

温度对黏土力学特性具有重要影响,温度变化将引起黏土的体积变形发生变化,并对其前期固结应力、剪切强度、弹性模量等具有重要影响。基于黏土"热陷"特性,引入热屈服面以描述不同超固结比的黏土在温度升高时所产生的塑性变形,并进一步开展以下工作:(1)建立考虑温度影响的下加载面模型,由于保留了下加载面模型对超固结黏土应力–应变特性优异的描述能力,并考虑了温度对黏土的2种作用(即温度使超固结黏土的超固结比降低和温度塑性应变对屈服面的硬化效应),该模型可以描述温度变化对不同黏土力学特性的复杂影响;(2)证明了所提出的模型严格满足热力学第一、第二定律;(3)采用该模型模拟Pontida clay和MC clay在不同压力下的排水加热试验和在不同温度下的三轴排水/不排水试验,模拟结果与试验结果对比分析表明,模型能合理地描述不同超固结比的黏土在温度变化时产生的体积变形以及温度对黏土强度的影响等。

THERMO-ELASTO-PLASTIC MODEL FOR SATURATED CLAY BASED ON THE CONCEPT OF SUBLOADING SURFACE

The coupled thermo-mechanical behavior of saturated clays is summarized，including the temperature effects on volume change，pore pressure，preconsolidation pressure，strength and elastic modulus. Based on the experimental results，a thermal yield surface is introduced to describe the temperature-induced reversible and irreversible volume change of saturated clay. A subloading surface model was extended to consider the temperature effects was established. The extended model can depict the decrease of preconsolidation pressure of overconsolidated clay and the hardening of yield surface by temperature-induced plastic strain. The model was then proved to strictly satisfy the thermodynamic theorems. With the developed model，numerical simulations of drained heating tests，drained and undrained triaxial compression tests of clay with different OCR under different temperature are performed. The simulated results was compared with existing test results，which shows that the model can describe the volume change induced by temperature change，the thermal softening effect on overconsolidated clay and thermal hardening effect of normally consolidated clay.