中文摘要：

基于过渡段相变的二维传热分析模型,对未来50年青藏铁路路桥过渡段温度场进行分析与预测,并定量研究过渡段高度和冻土类型对路桥过渡段长期热稳定性的影响。计算结果表明：①路桥过渡段下冻土上限由第5年的天然地表以上2.5 m,下降到第50年后的天然地表以下4.3 m,平均融化速率为15.11 cm/年；②过渡段冻土上限与过渡段高度呈非线性关系,随过渡段高度的增加,过渡段冻土上限先减小后增加；③随着冻土地基含冰量的增加,过渡段下融化盘径与最大融化深度逐渐增大,同时相同含冰量冻土地基融化盘径与融化深度的大小均随着距桥台距离的增大呈先增大后减小趋势,且最大融化深度均发生在距台前4m左右处。

英文摘要：

A 2-D numerical value calculation model of the permafrost roadbed-bridge transition section thermal field is established and finite element method is adopted to predict and compare the thermal field of different transition section heights and different types of permafrost in the coming 50 years. The calculation results show that roadbed-bridge transition section of permafrost table is predicted to drop from 2. 5 meters above the natural ground surface in the fifth year and to 4. 3 meters below the natural ground surface in the fiftieth year, and the melting rate is 15. 11cm/yearly. With the increasing of roadbed height, roadbed-bridge transition section of permafrost table first decreases and then increases. Meanwhile, the transition of thaw depth tends to climb up and the thaw bowl diameter increases and then decreases with the increasing of the distance from the abutment, and the maximum thaw depth locates about 4m ahead of the abutment.