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 implementedrnfor an extensive ground improvement operation that was critical to the success of thern“Cut and Cover” tunnel construction at the Bay.Area Rapid.Transit (BART)-FremontrnCentral Park Subway, Warm Springs Extension project in California. A combination ofrncomplex geologic conditions together with the seismically active Hayward fault and thernHayward Fault Aquifer, presented monumental challenges to the tunnel constructionrnoperations. A total of over 115,000 cubic meters (150,000 cubic yards) of jet groutedrnbottom plug was installed along the rail alignment to facilitate tunnel construction withoutrndisturbance to existing facilities and to mitigate groundwater infiltration into thernunderground construction areas. Advanced state-of-the-practice innovations in realtimerncomputerized quality control monitoring contributed to the successful completionrnof the extensive grout plug. An enhanced quality control program, including two fullrndepth limited initial production excavation cofferdams was proposed by the Contractorrnand accepted by BART. The comprehensive approach to quality control and the partneringrnefforts with BART to address the highly variable subsurface conditions andrnrelated quality control challenges led to an expedited start of both production jet groutrnoperations and follow-on tunnel construction activities. The jet grout plug work wasrncompleted ahead of schedule and within budget.