Slurry Walls for Bart Civil Center Subway Station

Site conditions, laboratory tests, design, construction techniques, ground-water control, and observation and stress measurements made during construction of a subway station in a 78-ft deep excavation in a heavily developed area for the San Francisco Bay Area Rapid Transit System, are described. The excavation was supported by Soldier Pile Tremie Concrete (SPTC) walls consisting of permanent concrete walls cast-in-situ in slurry stabilized trenches and braced at three permanent and two temporary strut levels. The excavation was made in pervious sands, clayey silts, and layers of compressible peat. To minimize excessive settlements of adjacent buildings, the water table outside the excavation was controlled by recharge wells and checked by observations on piezometers. Measured pressures and inward wall deflections during and immediately after completion of the excavation are compared with predicted lateral earth pressures.