基于多孔介质理论的渠道基土温度场特性研究

视冻土为均匀各向同性的多孔介质,确定了不同冻结状况下的土壤热参数。根据热传导方程,建立了土壤冻结过程的二维变系数数学模型,通过全隐式差分方法,并采用交替方向差分格式,得到了随时间和空间变化的温度分布场的求解方法。利用土柱冻结解析解验证了数值模型。以整体式小型U形渠道为对象,研究了不同位置及深度的基土温度分布状况,并与野外观测结果进行了对比。结果表明,基于多孔介质理论确定土壤热参数可以简化非线性方程的求解,全隐式交替差分格式对于小型渠道基土求解温度场比较适用;由于渠道区域形状的不规则及其二维边界,导致地下水位、热流对渠道不同部位的温度分布具有不同的作用,阴坡温度普遍低于渠底,已冻区逐渐扩大,温度分布较均匀,正冻区渠道基土温度呈非均匀分布状态。

Characteristics of Soil Temperature Field of Canal Based on Porous Media Theory

Considering the frozen soil as uniform and isotropous material,the porous media theory was used to determine thermal parameters of soil under different freezing situation.A two-dimensional variable coefficient mathematical model of soil temperature was established based on the heat conduction equation,and the tempera-ture field which varied with time and position was obtained by means of the fully implicit difference scheme and the alternating direction implicit method(ADI),then,the numerical modeling method was verified by the analyti-cal solution of soil column.The soil temperature under an small integral U-shaped canal was simulated and ac-corded with in-site observation well.The results showed that porous media theory could simplify the solution of nonlinear equation,the fully implicit difference scheme and ADI were suited for small canal;Because of irregular-ity of the shape of canal and two-dimensional boundary,the underground water level and heat flux had different influences on temperature under different position.The temperature of shady slope was lower than bottom of ca-nal generally,the frozen area was enlarged gradually and the temperature field was uniform,meanwhile,the freez-ing zone was non-uniform distribution.