Authors: S. Norris, D. Young, W. Chen, M. Crow
Proceedings - Rapid Excavation and Tunneling Conference 2003; Pg 905-926; Society for Mining, Metallurgy and Exploration
Abstract
An 18.5 km (12 mile) long tunnel is being driven by four Earth Pressure Balance Tunnel Boring Machines (EPB-TBMs) of 4.7 m (15.5 ft.) diameter through alluvial sand, gravel, silt and clay above and below the groundwater table in Los Angeles beneath buildings, railroads, freeways and the L.A. River. Continuous automatic data recording of TBM operation and field inspectors' records, accompanied by monitoring of 5,000 surface reference points and 268 borehole extensometers were used to obtain information.
The paper explains the reason for selecting the method of EPB-tunneling to ensure stability of the tunnel and meeting of environmental requirements, and presents data collected to monitor and demonstrate the performance of the TBMs in the different ground conditions encountered.
