复杂温度路径下饱和黏土的耦合热响应试验研究及无网格数值分析

The coupled thermo-hydro-mechanical of saturated soil has important application value in many aspects, such as nuclear waste disposal, thermal energy storage, geothermal resources development and so on. In view of the current situation of slow development of related experimental research, the coupled thermo-hydro-mechanical response characteristics of saturated clay under variable temperature load (such as exponential and harmonic cycle change variation) are studied using a special hollow cylindrical axisymmetric coupling test device by which the temperature boundary conditions can be controlled. The appropriate free energy density function and entropy density function expression are selected, then based on the theory of mixed medium and the principle of non-equilibrium thermodynamics, the strongly coupled thermo-hydro-mechanical nonlinear control equations of a saturated medium are derived according to the basic conservation law. The numerical discretization of SPH for the derived coupled equations are complete, then a program is developed, using FORTRAN language, to analyzed thermo-hydro-mechanical coupling problems based on the unique advantages of the meshless SPH method. The numerical simulation of the indoor test is carried out, and the calculated results are compared with the experimental data to verify the validity of the coupled model, then a series of numerical experiments are carried out to further study the coupling effect of thermo-hydro-mechanical and its internal interaction mechanism.

饱和岩土介质热水力耦合问题在核废料处置、热能贮存、地热资源开发等多个方面有重要的应用价值。利用自行设计的中空圆柱轴对称温度边界条件可控的热水力耦合试验装置，鉴于相关试验研究发展缓慢的现状，研究复杂温度路径（如指数变化、简谐循环变化）作用下饱和黏土的热水力耦合响应特征。选定恰当的自由能密度函数和熵密度函数表达式，在混合介质理论及非平衡态热力学原理的基础上根据基本守恒定律，推导出非线性强耦合的完备饱和土介质热水力耦合控制方程组。给出所推导的完备耦合方程组的光滑粒子法数值离散格式，使用FORTRAN语言并基于光滑粒子法独特的优势开发热水力耦合的分析程序。对上述的室内试验开展数值模拟，将计算结果与已获得的试验数据进行对比来验证所给耦合模型的有效性，进而开展一系列数值试验深入研究热水力的耦合效应及其内在相互作用机理。

随着我国城市化进程的持续推进，高放射性废物科学的处置、地热资源的高效开采等诸如此类新型环境岩土工程的发展，正促进着人们对复杂温度路径下饱和岩土介质热水力耦合特性的研究，本课题的顺利开展具有现实的工程应用价值，可为环境岩土工程提供理论和技术支持。项目实施过程中利用一个特殊中空圆柱轴对称温度边界条件可控的热水力试验装置，重点研究变化温度荷载（如指数变化、循环变化）作用下饱和土介质的热水力耦合响应特征。根据混合介质理论并进行合理的假定，选定恰当的自由能密度和熵密度两个状态函数表达式，在基本守恒定律的基础上根据傅里叶定律、广义达西定律、及热弹性应力应变关系三个本构表达式，并考虑柯西公式及广义有效应力原理，使用一定的数学技巧得到了完备的饱和土介质热水力强耦合控制方程组。.完全耦合的热水力方程由于其数学微分方程高度的非线性及多场强耦合性质，基于典型的网格算法对该类问题求解时进行计算域离散、数值离散往往出现一些额外的困难，并且数值稳定性及因离散格式差异而引起的假扩散或色散问题也存在。然而，无网格光滑粒子法的一些独特优势可以有效解决这些数值问题。由此，针对所发展的饱和土介质完备的热水力耦合控制方程的强耦合及非线性的特点，给出其光滑粒子法数值离散格式后从无网格光滑粒子法基本原理入手并基于其独特的优势开发出热水力耦合的分析程序，将得到的模型用于室内试验的数值模拟，再将计算结果与已获得的室内试验数据进行对比，评价项目所给出的耦合控制模型的有效性.最后，开展了一系列数值试验深入研究水热力的耦合效应及其内在相互作用机理。.