冻结条件下土壤水热耦合迁移数值模拟的改进

Numerical simulation improvement of coupled moisture and heat transfer during soil freezing

根据冻结条件下土壤水分运动和热量迁移的基本方程，推导出了冻土水热耦合方程，并构造了采用变化的空间步长和自动调节时间步长的全隐式有限差分计算格式，使模型求解中的迭代计算过程大为简化，计算速度有很大提高。用本模型对张掖壤土的室内冻结过程进行了模拟，土壤水分、温度的计算值和试验值吻合较好。计算结果表明，该方法不仅能模拟冻结过程中土壤水分、温度的变化，且在计算中土壤含水量较低时不需要在冻结区引入冰的阻抗系数的概念，较好地改进了已有的数值模拟，为模拟各种不同条件下的土壤冻结过程创造了条件。

Based on the basic equations of simultaneous soil water and heat transfer during soil freezing, the coupled equation of moisture and heat is deduced. The equations are solved numerically by the finite difference method with variable space and time step. As a result, the iteration procedure is greatly simplified, and the calculation speed is improved. The model is used to simulate the laboratory freezing process of Zhangye loam, the simulated values of water content and temperature follow the measured values closely. It shows that this method can be successfully used to simulate the change of soil water and temperature process during soil freezing. Moreover, if the soil water content is lower, no ice impedance factor is needed in the simulation as usually do. The method proposed is an improvement to the traditional simulation.