RECENT ADVANCES IN COMPUTERIZED LARGEDIAMETER JET GROUTING TECHNOLOGY IN THE SANTA CLARA VALLEY BASIN FORMATION SAN FRANCISCO BAY AREA-BART WARM SPRINGS EXTENSION

摘要

A specialized high volume, computerized jet grouting process was implemented for an extensive ground improvement operation that was critical to the success of the “Cut and Cover” tunnel construction at the Bay.Area Rapid.Transit (BART)-Fremont Central Park Subway, Warm Springs Extension project in California. A combination of complex geologic conditions together with the seismically active Hayward fault and the Hayward Fault Aquifer, presented monumental challenges to the tunnel construction operations. A total of over 115,000 cubic meters (150,000 cubic yards) of jet grouted bottom plug was installed along the rail alignment to facilitate tunnel construction without disturbance to existing facilities and to mitigate groundwater infiltration into the underground construction areas. Advanced state-of-the-practice innovations in realtime computerized quality control monitoring contributed to the successful completion of the extensive grout plug. An enhanced quality control program, including two full depth limited initial production excavation cofferdams was proposed by the Contractor and accepted by BART. The comprehensive approach to quality control and the partnering efforts with BART to address the highly variable subsurface conditions and related quality control challenges led to an expedited start of both production jet grout operations and follow-on tunnel construction activities. The jet grout plug work was completed ahead of schedule and within budget.