Presentation by Victor Romero CPEng
The East Bay Municipal Utility District (EBMUD) in the San Francisco Bay Area recently completed a system-wide Seismic Improvement Program to protect their facilities from catastrophic damage. A primary focus of this program was on retrofitting the 80-year old Claremont Tunnel, which crosses the active Hayward Fault zone. A large earthquake on the Hayward Fault could generate enough right-lateral fault slip to effectively sever this important water supply lifeline. The retrofit project involved construction of a new bypass tunnel through the Hayward Fault zone, together with systematic contact grouting and localized structural repair of the existing concrete liner. Several innovative design measures were incorporated into the seismic retrofit design, including an oversized tunnel cross section, backfill concrete side drifts, seismic isolation of an internal structural pipe, and shear fuses in the final lining.
The cutter-soil-mixing (CSM) method, a construction technology relatively new to the United States, was used on a Contra Costa Water District project in northern California to construct 15- and 27-metre deep watertight shafts in difficult ground conditions. The shafts were used for a 275-metre long microtunnel crossing of Old River. This is the second known application of this technology in the U.S. for the construction of deep microtunnel shafts and the first known application using shotcrete-reinforced walls. The shafts penetrate soft saturated silts and clays and loose to dense sands. Existing construction techniques, such as secant piles and slurry walls, were either considered uneconomic or infeasible for the deeper shaft. Caissons constructed in the wet were initially considered the most feasible method for the ground conditions. Rather than specifying a design, however, a performance-based specification was prepared, allowing contractors to provide their own designs. The successful contractor, proposed the use of CSM. Shaft design, equipment features, construction, and quality control will be discussed.
When: Tuesday, 8 May 2012
Where: University of Auckland
Room # 3-403(light refreshments in the 4th floor foyer of Engineering Building as usual – kindly sponsored by Jacobs Associates)
Time: 17:30 Light Refreshments