青藏高原铁路多年冻土路堤的碎石层高度

分析表明路堤尺寸、形状和边界形式对碎石路堤自然对流效应的发生有显著影响,需要根据具体工程要求来确定路堤的压力边界条件。对4种压力边界情况的碎石路堤自然对流进行了数值计算,显示透气边界的碎石路堤自然对流降温效应为最强。最后,通过引入自然对流指数,提出了实际冻土路堤碎石层填筑高度的确定方法,具体给出了粒径为2cm~4cm、4cm~6cm、6cm~8cm和8cm~10cm的碎石层填筑高度,并对粒径为6cm~8cm的碎石层填筑高度进行了实验验证,结果表明,通过自然对流指数所确定的碎石层高度对实际冻土路堤工程的设计具有参考价值。

BALLAST LAYER HEIGHT OF RAILWAY EMBANKMENT IN QINGHAI-TIBET PLATEAU PERMAFROST REGION

The analysis shows that the sizes, shapes and boundary conditions of embankment impact substantially on triggering the natural convective effect in ballast embankments. Pressure boundary conditions of ballast embankment are dependent on engineering conditions. The numerical results on ballast embankments with four pressure boundary conditions show that the natural convection cooling effect in ballast embankment with air-permeable boundaries is the strongest. A natural convection index for representing the cooling effectiveness of winter-time natural convection in ballast embankments is introduced. The approach to evaluate ballast layer heights in railway embankments in cold regions is developed. Evaluating ballast layer heights of embankment with the grain sizes of 2cm-4cm, 4cm-6cm, 6cm-8cm and 8cm-10cm is performed. Validity of ballast layer heights with the grain size of 6cm-8cm was demonstrated experimentally. The test results show that the ballast layer heights in railway embankments evaluated by the natural convection index are available for design of ballast embankment.