CONSTRUCTION CHALLENGES OF THE CENTRAL SUBWAY’S TBM LAUNCH SHAFT AND STATION’S HEADWALLS

摘要

San Francisco’s growth requires additional transit solutions, which is why the SanrnFrancisco Municipal Transportation Agency (SFMTA) is building the Muni Metro TrnThird-Line Extension: Central Subway.rnThis $1.6 billion capital investment project features a 1.7-mile long, 21-ft. internalrndiameter twin bored tunnel. This paper describes the geotechnical conditions, urbanrnconstraints and the novel approaches adopted for the TBM Launch Shaft and the stations’rnheadwalls that the TBMs mined through. In particular, it will emphasize the specificitiesrnof building a slurry wall with 16-ft. headroom below an existing highway in service.