Phase 2 of the Third Street Light Rail Project is currently underway, which includes the construction of the Chinatown Station, cavern, crossover and cross-cut caverns using the Sequential Excavation Method (SEM).
Gall Zeidler Consultants provides expert design review services on the SEM tunneling for the Chinatown Station and associated SEM caverns, which includes review and recommendation of the following aspects of the work: construction staging, multiple drift excavation sequencing, structural design calculations, use of ground improvement measures for dewaterwing and grouting, settlement mitigation measures involving compensation grouting, structural design calculations, instrumentation and monitoring, waterproofing, contact packaging, and SEM specifications.
San Francisco, California
2009 – Present
Mined Underground Center Platform Stations with Ancillary Caverns
Cross Cut Cavern 2,700 square feet (250 square meters)
Station Caverns 2,300 square feet (213 square meters)
Cross Over Cavern 1,750 square feet (163 square meters)
Cross Cut Cavern 67 feet (20 meters)
Station Caverns 290 feet (90 meters)
Cross Over Cavern 310 square feet (95 meters)
Highly Deformed Fractured Rock, (Melange, Franciscan Rock Formation), Colluvium Consisting of Very Stiff, Brown and Gray Silty Clays, Old Bay Deposits, Sedimentary Marine Deposits, Fluvial Deposits and Fill
Approximately $1.5 Billion
PB Americas / Wong JV
San Francisco Municipal Transportation Agency (SFMTA)