Abstract:
Emerging from the Great Recession of 2008, San Francisco has experienced an era of construction growth unparalleled since the gold rush. This development has been concentrated in the Transbay and South of Market Districts, and nearby Mission Bay. As the decade has progressed, basement excavation depths and the density of building close to historic and recently completed structures have both increased. These construction challenges are compounded by heightened sensitivity to ground deformation and impacts on adjacent structures and facilities, driven in part by the Millennium Tower project. Soil mix shoring systems are the preferred Support of Excavation solution in San Francisco and are employed almost exclusively for excavations below groundwater. Project examples will illustrate the development of San Francisco soil mixing over the last decade, highlighting the ground conditions which make soil mixing so prevalent, and presenting state of practice in terms of field execution, quality control, and design and risk management considerations.