Abstract:

A highway tunnel in Xiameng crosses underneath operating YingtanXiamen railway line and turnout section with small clearance. Countermeasures, such as threelayer lining structure (primary reinforcement, first insitucast concrete lining and secondary insitucast concrete lining), 299 superlong pipe curtain installed in circular form, preconsolidation of ground by deephole grouting on the tunnel face and around the tunnel contour, 6step tunnel excavation by double side drift method, are taken. In the end, the tunnel crosses the railway successfully. 

Key words: highway tunnel under supershallow cover, tunneling underneath existing railway line, railway protection, superlong pipe curtain, threelayer lining, double side drift method, sixstep excavation