Abstract:

New underground works that are located in soft ground with close proximity to existing underground works are often encountered. The D district of Fengshengding underground street tunnel in Shenzhen is a typical urban underground works that passes over existing tunnels in soft ground with small spacing. The underground street tunnel passes underneath Shennan road, where a lot of utility lines are buried, and at the same time passes over two Metro tunnels. The minimum overburden of the underground street tunnel is 3.9m and the structural span of the underground street tunnel is 13.7m. The spacing between the bottom of the underground street tunnel and the roof of the Metro tunnel is only 0.33m. Therefore it is very difficult to control the ground deformation. In order to verify the rationality of the design and construction scheme of this project, the authors predict the deformation of the ground and Metro tunnels by threedimensional numerical simulation made by FLAC3D, based on the characteristics and design and construction scheme of the project. The authors conclude the deformation distribution regulation of extrashallow underground works passing over existing tunnels with small spacing, which can provide reference for similar projects in the future.

Key words: ground deformation prediction, soft ground, close proximity, excavation under shallow cover, numerical simulation, underground street