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Author      Title/Abstract      

THE PAINT WAS LIKE NEW – New EPB Machine Manages Risk in San Jose Tunneling
Author: Robert Allen, Robert Kahl (DCM Engineering), Gil Garcia (Akkerman)
Date: 3/206
No Dig 2006 Conference

The San Jose 60-Inch Brick Interceptor Replacement – Phase IB Project replaced and realigned the existing West Brick Interceptor Sewer with a new 9,000-foot-long 84-inch-diameter pipeline. The new pipeline was installed by conventional open-cut trenching with the exception of four critical undercrossings which required trenchless pipeline installation of RCCP. The undercrossings included four-lane divided highway, City streets, county light rail system, and the City of San Francisco’s Hetch Hetchy water supply Aqueducts. The tunnel invert depths varied from 17 to 35 feet and were about 7 to 25 feet below groundwater. The contractor was given the option of using a Tunnel boring Machine (TBM), Earth Pressure boring Machine (EPBM), or Microtunnel Boring Machine (MTBM) for Undercrossing No. 1 and No. 2 which consisted of predominantly stiff clay soils. For Undercrossing No. 3 and 4, optional equipment was limited to EPBM or MTBM due to predominantly non-cohesive sands exhibiting flowing to fast raveling behavior. The contractor selected a 104-inch outside diameter Akkerman Tunneling Shield with backhoe excavator and hydraulic closable doors for Undercrossing No. 1. For Undercrossing Nos. 2, 3 and 4, the contractor selected a 102-inch outside diameter Akkerman-Hitachi Zosen Earth Pressure Balance Shield. The new EPBM completed all three tunnels very efficiently and safely eliminating concerns of ground settlement due to potential flowing and fast raveling ground conditions especially at the Hetch Hetchy Aqueduct undercrossing. This paper discusses tunnel shaft construction, ground treatment, shaft dewatering, and the operation of the 102-inch EPBM including the use of soil conditioners, muck removal, jacking forces and lubrication and production rates.

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