Monitoring Earth Pressure Balance Tunnels in Los Angeles

ABSTRACT: Tunneling using earth pressure balance (EPB) tunneling methods has been active in Los Angeles over the last seven years. Three recent large-diameter EPB tunnel projects have been completed to create approximately 32km (20 miles) of precast concrete lined tunnel excavated through alluvial soils and soft, sedimentary rock. This paper addresses monitoring of ground surface subsidence using data collected from geotechnical instrumentation and TBM performance parameters. TBM operating data are used in conjunction with surface-installed instrumentation to predict surface subsidence. TBM operations may then be adjusted to reduce potential settlementrelated damage to adjacent structures or utilities. Monitoring instruments using remote access is also addressed. The paper provides case histories of successful performance monitoring to support future urban tunneling projects