冻土块石路基的保冷效果数值计算研究

Numerical Simulation on the Cooling Effect of Gravels Embankment in Permafrost Areas

应用有限体积法,对一块石路基内的温度与速度特性进行了数值计算分析。计算结果表明块石路基的热稳定性较好。在路基内,越远离地表,监测点的温度变化越滞后于地表。而且离地表越远,温度变化幅度越小。在对块石路基内的块石层计算中采用了"块石"与"多孔介质"模型。两种模型计算的块石层内空气速度场在冬季都呈现一个逆时针旋转的涡,在夏季则是顺时针旋转的涡。由于块石模型计算的速度更加直接地反映了块石空隙中空气的真实速度,所以其计算结果大于多孔介质模型计算的速度。采用块石模型计算出路基内的整体温度略低于采用多孔介质模型计算结果。本文认为采用块石模型计算块石路基的速度场与温度场优于多孔介质模型。

Time-varying temperatures and pore air velocities in the special ballast embankment are investigated using the finite volume method and the results are visualized in the form of isotherm and velocity vectors for different times of the year. It can be concluded that the special ballast embankment can cool the permafrost beneath, thus ensuring its thermal stability. In addition, the deeper the points are away from the native surface, the slower the temperature variations lag behind the surface and the smaller the temperature variations are. Two models, the ballast model and porous model, are applied in the simulation. Simulation results show that there is a well-defined counter-clockwise rotation of the pore air extending throughout most of the embankment for both the two models during winter months. Whereas in summer there is a gentle clockwise eddy formed in the embankment. The velocities gotten from the ballast model reflect the true flow of pore air in the embankment and thereby are somewhat higher than those computed from the porous model. When the ballast model is used, the temperatures for the whole embankment are somewhat lower compared with those gotten from the porous model. Consequently the ballast model has more advantages to simulate the flow and heat transfer in the special ballast embankment than the porous model.