Abstract: To ensure the construction safety of super-large rectangular pipe jacking shield tunnel adjacent to the high-speed railway, based on an actual railway related project, the safety of super-large rectangular pipe jacking shield close to high-speed railway in soft stratum is studied. The results show that the track settlement and pipe segment safety factor far exceed the control threshold during the construction, so the reinforcement scheme must be adopted. The track settlement can be reduced by 58.20% and the minimum safety factor of pipe segment can be increased to 1.35 by adopting advance grouting scheme. Using manually dug pile and D-shaped beam can reduce the track settlement by 63.05% and increase the minimum safety factor to 9.49. After adopting the pile-plate reinforcement scheme, the track settlement can be reduced by 70.90% and the minimum safety factor can be increased to 9.00. The reinforced effects of manually dug pile and D-shaped beam scheme and pile-plate scheme is significantly better than that of advance grouting. It is recommended to adopt the pile-plate scheme in the section under the high-speed railway to be built, and the manually dug pile and D-shaped beam scheme in the section under the existing high-speed railway. The on-site monitoring results show that the maximum surface settlement caused by pipe jacking tunneling is 3.25 mm after the super-large rectangular pipe jacking shield passes through the Fuzhou-Xiamen railway section to be built. After the manually dug pile and D-shaped beam is adopted for the existing Hangzhou-Shenzhen section, the maximum settlement of the high-speed railway track is only 1.65 mm. Both track settlement and surface settlement are far less than the settlement threshold. The super-large rectangular pipe jacking shield successfully crosses the Fuzhou-Xiamen Railway and Hangzhou-Shenzhen Railway. The research conclusion can provide reference for similar large-scale tunnel proximity engineering.

Key words: tunnel engineering, rectangular pipe jacking shield tunnel, approach construction, reinforcement scheme, weak stratum