为了研究块石路堤降温效应与块石层高度之间的关系, 基于多孔介质自然对流理论和热传导理论引入了表征寒区块石路堤自然对流降温效应的自然对流指数, 利用热传导温度分布函数获得了路堤自然对流指数随块石层高度变化的近似公式。分析表明:自然对流指数最小值对应于路堤块石层的最小高度, 而其最大值对应于路堤块石层的最大高度。另外介绍了一种利用自然对流指数近似公式估算路堤块石层临界高度的方法, 并具体给出了算例, 最后进行了数值验算。结果表明:通过自然对流指数确定的临界高度可为寒区工程的路堤设计提供参考。

In order to research the relation between the cooling effect and ballast layer height, the natural convection index for representing the cooling effect of natural convection of ballast embankment in cold regions was introduced based on the natural convection theory and the thermal conduction theory in porous media. The approximate formula of the natural convection index varying with the height of ballast layer was obtained using a thermal conduction solution of the temperature distribution in the ballast layer. The research shows that the minimum of natural convection index corresponds to the minimum of height of ballast layer in embankment, and the maximum of index corresponds to the maximum of ballast layer height. An approach to evaluating the critical heights of ballast layer based on the approximate formula of the natural convection index was investigated.Examples was presented and numerical check was carried out.The result shows that the critical heights based on the natural convection index can refer to design of embankment in cold regions.