Construction Counter Measure Of The Engineering In Permafrost Area On Contract No.14 Of Qinghai-Tibet Railway

Qinghai-Tibet railway, 1956km long, starts from Xining of Qinghai province to Lhasa of Tibet autonomous region. The being built section of Golmud and Lhasa is 1142km long. The construction is faced with the severe challenge of such three big difficulties as many years permafrost, high-altitude cold and oxygen lack and fragile ecology, with hard engineering works, high requirement and great difficult. Qinghai-Tibet plateau is called the roof of the world and the third pole of globe, and it is the source of major rivers. In such primitive, oblique, fragile and sensitive geology environment, the built Qinghai-Tibet railway is the high plateau railway of the highest altitude above sea level and longest line in the world, crosses the maximum height of Tanggular 5027m, runs 960km long above the sea level of 4000m and over 550km of frozen earth zone. As the weather is chill, and the surface mobile layer thaws and freezes with the change of seasons, below the surface is the frozen earth layer. Under such geology condition, the railway construction destroys the original surface heat balance and ecology environment, freezing swelling, thawing sinking, and crack are the most common diseases of railway buildings, if such disease happens to the engineering structure below the subgrade bridge and culvert, it will affect the train comfort or heavily make traffic unsafe. Our country firstly put forward such design principle of Qinghai-Tibet railway engineering as "lower temperature actively, reduce the heat into the subsoil, and assure the heat stability of frozen earth for the quality stability of construction", creatively adopt such corresponding measures of frozen earth construction problem as: for the poor frozen earth developing section, line should avoid as possible;for the geology of ice at high temperature and unstable frozen earth zone, the method of bridge instead of subgrade shall be adopted;in subgradeconstruction, such facilities as heat stick, rubble ventilation subgrade , rubble ventilation berm, ventilation pipe subgrade and laying heat preservation board etc shall be adopted to raise the stability of frozen earth subgrade;during the excavation of bridge, culvert , foundation pit and scouring prevention trough, creatively adopt single-tooth knapper and solve the problem of frozen earth excavation;during the construction of bridge and culvert, durable concrete and three-step maintenance method are adopted to assure the outside and inside beauty of structure. This text mainly talks about the treatment with the permafrost construction and its results, which is of guidance significance for similar engineering work. The monitoring data shows that at present most subgrade deformation is not more than 2cm in frozen earth zone, the bridge foundation deformation all satisfy the design requirement and the engineering buildings in permafrost zone are basically stable.