准饱和正冻土水热力耦合模型的扩展有限元程序研发

Development of the extended finite element program for the thermo-hydro-mechanical coupling model of quasi-saturated freezing soil

针对冻土冻融过程中存在移动相变界面及材料分区不断变化的特点,基于已建立的能全面地描述冻土的水、热、力与变形实际状态的准饱和冻土耦合模型,推导土颗粒、水和冰颗粒的温度场、变形场及水分场的扩展有限元解析格式,构建水热力相互作用在程序中实现的具体方法,开发一款能够为实际冻土工程服务的耦合分析平台3GEXFEM,利用程序对Fukuda系列试验进行数值模拟,分析得到的温度场、水分场与变形场与试验结果较一致,验证了程序的合理性和先进性。此外,基于程序系统地研究不同环境条件:上覆压力、温度梯度、变温模式、温变速率对冻土冻结过程中水热力耦合的影响,为模型及程序的工程应用奠定了基础。

A method based on the extended finite element（EFM） was proposed to overcome the problem in modeling the multi-field coupling in permafrost engineering which has the characteristics of moving interface of phase transition and changing material zones. A theory capturing various couplings among the liquid transport within the pores,the force interaction between the soil skeleton and crystal ice,the energy jump during the phase-changing between ice and water was used. The governing equations for solving the primary field variables such as temperature,liquid pressure and solid displacement were derived and an analysis platform 3 GEXFEM was developed. The validation of the program was accomplished by means of the numerical simulation to an experiment published by Fukuda. The results of the simulation of the temperature field,moisture distribution and heave agreed well with the experimental results. In addition,the moisture-heat-stress coupling of frozen soil during freezing process was solved under different environmental conditions such as overburden pressure,temperature gradient,temperature change mode and cooling rate, showing that 3 GEXFEM program are well adapted for practical engineering.