青藏铁路主要冻土路基工程热稳定性及主要冻融灾害

在介绍青藏高原多年冻土退化背景及其工程影响的基础上,通过主要冻土路基现场监测和沿线调查,对青藏铁路冻土路基2002年以来的地温发展过程、热学稳定性及次生冻融灾害进行了分析。结果表明：青藏铁路自2006年通车后冻土路基整体稳定,列车运行速度达100 km/h,达到设计要求,但不同结构路基的热学稳定性不同,采取＂主动冷却＂方法的路基稳定性显著优于传统普通填土路基。管道通风路基、遮阳棚路基及U型块石路基冷却下伏多年冻土的效果显著,块石基底路基左右侧对称性较差,而处于强烈退化冻土区和高温冻土区的普通路基热稳定性差,需结合路基所在区域局地气候因素予以调整或补强。以热融性、冻胀性及冻融性灾害为主的次生冻融灾害对路基稳定性存在潜在危害,主要表现为路基沉陷、掩埋、侧向热侵蚀等,其中目前最为严重的病害是以路桥过渡段沉降为代表的热融性灾害。

Thermal Stability of Roadbeds of the Qinghai-Tibet Railway in Permafrost Regions and the Main Freezing-thawing Hazards

The background of permafrost degradation in the Qinghai-Tibet Plateau and its engineering impact in the region were introduced.Then based on the results of geo-hazard investigations and ground-temperature monitoring of the roadbeds along the Qinghai-Tibet Railway in the permafrost regions,the development of ground temperature,thermal stability and secondary freezing-thawing hazards since 2002 were analyzed.The results showed that the roadbeds in the permafrost regions are stable in the whole since it was open to traffic in 2006.The train speed reaches 100 km/h,which achieves the design requirements.In-situ monitored results indicated that thermal stability of the roadbed constructed with a principle of ＂active cooling＂ method is much better than that of traditional roadbed.Among the cooling roadbeds,the duct-ventilated roadbed,sunshine-shield roadbed and U-type crushed-rock roadbed efficiently cooled the below permafrost.The roadbed with crushed-rock basement is unsymmetrical in thermal regime,and the thermal stability of the traditional roadbed is very weak,especially in the regions where permafrost is under intense degradation.Such sections should be reinforced considering the local climate factors.Along the railway,some main geo-hazards include thawing settlement,frost-heave and freezing-thawing induced hazards,and all of them might potentially influence the roadbed stability with settlement,burying and laterally thermal erosion.Currently the most serious one is the roadbed settlement in embankment-bridge transition section.