Abstract
Shield tunneling activities inevitably pass through pile foundations at close distance in densely urban areas. Various studies have investigated the interaction between newly constructed tunnels and existing pile foundations. However, the influence of different construction sequences of twin paralleled shield tunneling on single long pile is seldom considered. A case was found in the project of Changsha Metro Line 5, where the twin paralleled tunnels were constructed near the Wanjiali Viaduct piles. A three-dimensional finite element model was established to analyze the pier settlement, ground surface settlement trough, and the vertical and horizontal displacement of pile under different construction sequences in layered soil. The results show that the adjacent pile and surrounding environment are affected substantially with the change of construction sequence of twin paralleled tunnels. The construction sequence of condition (b), in which the tunnel closer to the pile foundation is first constructed and then the tunnel farther away from the pile foundation is second constructed, can reduce the settlement of pier by 13.1%, the maximum surface settlement by 7.0%, the maximum vertical displacement of pile foundation by 7.9%, and the maximum horizontal displacement by 6.9%. The present findings can provide reference for similar projects.
Highlights
With the increasing congestion of surface traffic, exploiting the potential and promoting the benefits of the subsurface in cities have become an indispensable approach
A growing demand on housing, viaduct, infrastructure, and open space is competing for the urban surface areas, and the subsurface, which makes shield tunneling often needs to pass through lots of pile foundations
Sirivachiraporn and Phienwej [15] analyzed the field measurement data of Advances in Civil Engineering the first Bangkok subway project to evaluate the ground movement characteristics and responses of adjacent buildings. e results indicate that buildings on long piles showed the least induced settlements
Summary
With the increasing congestion of surface traffic, exploiting the potential and promoting the benefits of the subsurface in cities have become an indispensable approach. Different construction sequences of twin paralleled shield tunnels will certainly make some differences in ground surface settlement and displacement of pile foundation. Few scholars study the effects of different construction sequences by performing numerical calculation method to systematically analyze the influence on adjacent pile foundations. In view of the aforementioned issues, it is of great significance to study the effects of different construction sequences on ground surface settlement and displacement of single pile due to twin paralleled shield tunneling. Combined with field measured data, the changing trend of bridge pier settlement and the results of ground surface settlement and displacement of pile foundation caused by shield tunneling under different construction sequences are analyzed. Through the comparative analysis of the data, the most appropriate construction sequence of the twin paralleled shield tunnels passing through the pile foundation is proposed, which provides reference for similar projects
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