Discussion on Permafrost Hazards of Railway Engineering and Prevention Measures: A Case Study on Qinghai-Tibet Railway

The Qinghai-Tibet Railway(QTR) is the highest and longest plateau railway in permafrost region in the world. The Qinghai-Tibet Railway in permafrost area locates in the hinterland of Qinghai-Tibet Plateau, which belongs to a low latitude, high altitude permafrost area. In this area, that the poor thermal stability, high ice content, and many other complex factors seriously impacts survey and design of The Qinghai-Tibet Railway. Permafrost is a special soil, it has many features different from the ordinary soil. And permafrost thawing layer has seasonal freezing-thawing process every year, along with a few of adverse geological phenomenon, which results in a series of engineering problems. This paper introduces the basic characteristics of permafrost along Qinghai-Tibet Railway, expounds the permafrost hazards of railway engineering, such as frost heaving, freeze thawing, frost boiling of roadbed, thaw collapse and mud flow, bridge foundation frost heaving and thaw settlement, deformation and cracking, culvert foundation freeze-thaw deformation, tunnel lining frost heaving and so on. Briefly analyzes the influence mechanism of permafrost to railway engineering. And then, proposes a temporary prescript for the railway engineering in different type of permafrost area. It is that each engineering in different area has to adopt different design concept and different prevention measures. At last, proposes the prevention measures and suggestions for the railway engineering in the permafrost region, such as reasonable control of embankment height, rubble air-cooled embankment, crushed stone slope protection with thermal insulation subgrade, heat pipe subgrade, ventilating pipe subgrade and so on.