正冻土中的水热耦合模型

A model of coupled heat-fluid transport in freezing soil

根据温度梯度诱导薄膜水迁移的冻胀机理 ,建立了模拟标准样品无盐土冻胀过程的水热耦合模型 .模型需要输入的参数包括 :干密度、含水量、孔隙度、未冻水含量 (- 1℃ )、导热系数、渗透系数及边界温度条件、冻结周期和时间步长等 .计算结果包括 :冻胀量、冻结深度、冰分凝温度、冻结缘厚度 .通过与实际冻胀实验结果比较 ,模型所预测的冻胀量和冻深与实测值相差分别为 1.12 %～ 15 .77%和 5 .38%～ 10 .35 % .冻结缘的厚度变化在时间上有三种方式 :即持续增大、增大后逐渐减小。

A model for simulating frost heave in a saturated and salt-free standard specimen column was developed,which is based on the frost heave mechanism of film water migration under temperature gradients.In this model,soil column is divided to three parts:frozen part,fringe part and unfrozen part.It assumes that the temperature gradient and the thermal conductivity are constant in each part,the permeability and water content in unfrozen part are constant,unfrozen water content varies with temperature in experiment,and the fluid in fringe and unfrozen part are steady and follow Darcy’s law,the water in frozen fringe is not assemble.The freezing temperature and segregational temperature are solved by Laplas’ Equation and Darcy’s law.The permeability in fringe and frozen soil solved by porosity and initial permeability.The input parameters include the boundary temperatures and the length of soil column as well as the dry density the porosity,the water content,the unfrozen water content at -1℃ ,the permeability,the thermal conductivity of soils,the freezing time and the time step for computation.The computed results include heave amount,frost penetration,segregational temperature as well as the thickness of frozen fringe and distribution of ice lens.The segregational temperature varies much at beginning and stable in following time compared with tested results,the deviations of simulated heave amount and frost penetration are 1.12%～15.77% and 5.38%～10.35% each other.The thickness of frozen fringe changing with elapsed time has three models of increase,stableness and decrease.