Staged construction on soft clay: A design case history

摘要

The Hamilton Army Airfield Wetlands Restoration project involved the construction of more than 8 kilometers of levees over deep deposits of soft high plastic clay, along the margins of San Francisco Bay. The levees will contain extensive hydraulic filling that is part of the wetlands restoration program. This paper addresses the staged construction design at the North-1 section of the levee system. Staged construction was used to improve the stability of the new proposed containment dike and wetlands fill, and reduce post-construction settlements. The Stress History And Normalized Soil Engineering Properties (SHANSEP) design procedure was used to develop the shear strength parameters that were necessary for the evaluation of stability at different stages during construction. The design process was based on extensive in-situ field vane testing and a comprehensive laboratory testing program. The use of vertical wick drains was evaluated for different areas along the levee. Various consolidation periods between construction stages were considered, and their impacts on shear strength increase assessed.