Abstract:

Due to the existence of ground water, swelling and thawing caused by freezing always occur to tunnels located in extremely cold regions. Therefore, the tunnel structure may be damaged and the service life of the tunnel may be reduced. For the waterproofing and drainage of Lafashan tunnel, which is located in extremely cold region, the design principle of “water stopping, water draining and water sealing” is established, i.e., waterstopping grouting is made to stop the ground water so as to minimize the water behind the lining, then heatkeeping layer is installed behind the lining to avoid freezing behind the lining, and finally central drainage ditch is built below the freezing level so as to ensure smooth water releasing. In this way, the problem of freezing swelling in extremely cold regions has been successfully solved. Regarding the construction of the waterproofing and drainage system, new heatkeeping layer installation method is developed, the water stop tie installation technique is optimized and special steel formwork is adopted to facilitate the installation of the longitudinal steeledge water stop tie, buried water stop tie and lining water stop tie. In this way, the normal defects of the waterproofing and drainage system of tunnels have been successfully avoided.

Key words: Lafashan tunnel, extremely cold region, heatkeeping waterproofing and drainage system, heatkeeping material