Midas GTS NX: Bridge Construction above Existing Underground Railway Tunnels

Jong-ho, Shin, Jeong-ho, Moon, In-keun, Lee, Kee-yeon, Hwang

"ABSTRACT

A river restoration work named ‘Cheong-gye Cheon Restoration Project’ launched in July 2003 in Seoul, Korea. The project includes construction of 21 new bridges. Four bridges among them were planned above running tunnels which are about 10m below ground surface, and of which axis is parallel to bridge axis. All bridges were for heavy vehicle traffic. The subway tunnels were constructed by the sprayed concrete lining method (SCL), i.e., NATM, in between 1983 and 1995. In design phase several measures to reduce the impact of bridge loads on the railway tunnels were considered. It was required to design bridge abutments to avoid eccentric loads on the tunnel and reduce stresses causing any structural harm to the running tunnels. Balance of construction loads was the main issue during construction. Two different foundation methods were employed: piledfoundation and grouted-foundation. To evaluate the behaviour of ground and tunnel, three dimensional numerical modelling was performed using the computer program MIDAS/GTS. Construction management program including intensive instrumentation of the running tunnels was implemented to secure safe construction. The bridges were successfully completed without damages to the running tunnels. Design analysis, instrumentation and construction performance are presented and reviewed in this paper. It is found that the piled-foundation is beneficial in reducing the impact of the bridge load, meanwhile the grouted-foundation is more cost-effective."