Ground Improvement to Enhance Bulkhead Seawall Stability

The seismic design and construction issues associated with new bulkhead seawalls at the Port of Los Angeles (POLA) are addressed, including ground treatment applications to enhance seismic performance. Because the POLA is located in a highly active seismic zone, the bulkhead seawall design had to consider the cyclic behavior of soft clayey soils and potentially liquefiable dredged backfill behind the new bulkhead seawall. Because of legal and environmental constraints, the geotechnical exploration of the bulkhead seawall alignment was limited. Based on the available geotechnical information and the bulkhead configuration, deep soil mixing (DSM) ground improvement was specified behind the seawall to reduce the static and seismic lateral earth pressures. However, the subsurface conditions encountered during construction were different than assumed based on the initial, limited geotechnical exploration. DSM was substituted with jet grouting for much of the new bulkhead seawall alignment to accommodate the actual subsurface conditions. The purpose of this paper is to discuss the development of the ground improvement program and illustrate the potential influence of variations in the subsurface conditions on construction methods and project execution.