季节冻土区风积沙土路基冻结过程中水热迁移数值分析

基于Harlan模型和Darcy定律,并考虑温度梯度对水分迁移影响、温度和含水量对水热参数影响以及各种环境气候因素的影响,建立了完全依赖气象资料和水热参数的风积沙土路基冻结过程中水热耦合迁移数学模型,采用全隐式有限差分格式和TDMA迭代法对内蒙古锡林浩特地区沙漠公路207国道K135+000处冻结期间路基水热迁移规律进行了数值模拟.结果表明:该地区道路冻结深度随时间近似线性变化,冻结速度达到2~3 cm·d^-1,最大冻深为3 m左右,冻融时间约为180 d;水分迁移主要发生在冻结锋面附近,从未冻区向冻结区迁移,且随着冻结锋面前移,迁移量逐渐增大;整个冻融期间最大冻深底部层位含水量变化较大,路面下0~50 cm范围内温度变化比较剧烈.

Numerical Analysis of Coupled Moisture and Heat Transfer within a Freezing Aeolian Sandy Embankment in Seasonally Frozen Soil Regions

Based on Harlan model and Darcy law,in this paper,a mathematical model is established of coupled moisture and heat transfer within an aeolian sandy embankment during freezing period,which wholly depends on meteorological data and parameters of moisture and heat,considering the temperature gradient that influences moisture transfer,temperature and water content that influences moisture and thermal parameters,effects of meteorological-environmental factors.On the basis of the model validation,a numerical simulation is made for the moisture and heat transfer at K135+000 of National Highway No.207,a section of desert road,in Xilin Hot of Inner Mongolia during freezing period,by means of total implicit finite difference scheme and TDMA iterative method.The simulation shows that the road frozen depth is approximately linear variation with time,the frozen speed is 2~3 m·d^-1,the frozen depth is about 3 m,the frost time is about 180 days;and that moisture transfer mainly takes place in the frozen fringe,moisture moves from unfrozen area to frozen area,water content decreases 25%～30% beneath the frozen fringe and water transfer increases gradually with movement forward of the frozen fringe;and that the maximum water content variation is at the bottom of the maximum frozen depth,while temperature varies extremely in 0~50 cm of the pavement depth and the difference between the highest and the lowest temperatures is 30.5℃,24.5℃,18.9℃ in 0 cm,20 cm,50 cm depths within the pavement in all time of the freezing and thawing period.