THE COPENHAGEN METRO CIRCLE LINE-TUNNELLING AND STATION CONSTRUCTION CHALLENGES IN URBAN CONDITIONS

摘要

The paper will describe challenges for design and construction of the tunnels andrnstations in soft ground conditions in an urban environment for the Copenhagen MetrornCircle Line. The project consists of 15.5 km metro line with 17 underground stations.rnThe ground conditions are 10–15 m of glacial deposits overlying a limestone, whichrnare fissured and include hard layers of flint. The stations will be constructed as Cut &rnCover structures using top-down construction technique and retained within a stationrnbox of either secant piles or diaphragm walls. The tunnels located in the glacial depositsrnand in the limestone will be constructed using closed face TBM’s of either EPB orrnslurry type. As many of the old buildings in Copenhagen are founded on wooden pilesrnwhich will deteriorate if exposed to oxygen, there are requirements for not loweringrnthe groundwater table. One of the major challenges for the project is to control therngroundwater during tunnel and station construction. A system of combined dewateringrnand recharge of groundwater in places in combination with grouting will be utilised. Thernpaper describes the challenges in selection of construction methods dealing with thernstrict requirements for groundwater control, noise and vibrations and settlement control.rnThe project is tendered as a design and construct project during summer/autumnrn2010 and construction contract signed in January 2011.