Seismic Performance of a Deep Soil Mixing Grid: A Magnitude 7.1 Load Test at the Port of Alaska

The Port of Alaska in Anchorage (Port) has embarked on a multiphase modernization program that includes the development of a new petroleum and cement terminal (PCT) berth. The berth consists of a pile-supported trestle that connects to a platform located offshore in the Knik Arm waterway (Figure 1). The terminal is located in a dynamic marine environment with numerous design challenges, including tidal fluctuations of as much as 40 ft, design ground motions associated with a magnitude ${\mathrm{M}}_{\mathrm{w}}$ 9.3 subduction zone earthquake, weak foundation soils, and shoreline conditions that are vulnerable to large-scale seismic displacements. Geotechnical input to the seismic design of the pile-supported terminal required synthesis of extensive in-situ and cyclic laboratory testing data, nonlinear deformation analysis (NDA), and layout of a deep soil mixing (DSM) ground improvement zone for mitigation of seismically induced slope displacements.