Abstract: In order to ensure the implementation of the first longdistance shield tunnel crossing underneath airport area in waterrich sandy cobble strata in China, as well as connection gallery of tunnel project by freezing method in Chengdu, measures, i.e. project comparison, expert demonstration, design optimization, numerical calculation and field monitoring data analysis, are adopted, and a series technical measures, i.e. optimization design of overall engineering planning, optimization of shield configuration, clay shock method, land sonar cavity detection, pregrouting for connection gallery and water stop by of freezing method, etc., are put forward. The practical results show that: (1) Major technical problems of longdistance shield tunnel crossing underneath airport area in waterrich sandy cobble strata can be successfully solved by using shield construction method, optimizing the horizontal and vertical crosssection design, adding a middle ventilation shaft to greatly reduce the single driving distance of shield to about 1 km, and adopting strict settlement control measures. (2) The composite water stop scheme proposed, i.e. water stop in tunnel by double grouting + freezing reinforcement, can achieve good effect in waterrich sandy cobble strata.

Key words: shield tunnel, waterrich sandy cobble strata, airport area, clay shock method, connection gallery, freezing method