Liquefaction Failure and Remediation: King Harbor Redondo Beach, California

Liquefaction failure, including large lateral displacements and associated settlement, severely damaged marina facilities at Redondo Beach King Harbor during the Northridge Earthquake of January 17, 1994. Although minor ground deformation apparently occurred in several areas of the harbor, severe damage was restricted to the central portion of Mole B, one of four offshore fills constructed as a part of marina improvements in 1960–61. Local ground conditions and methods used to remediate liquefaction are presented and discussed. Two ground modification techniques were used to mitigate the liquefaction potential of the reconstructed Mole B facilities. The major portion of the failure area was treated with vibroreplacement stone columns. Vibratory displacement and installation of the gravel columns not only densified the foundation soils, but also provide additional strength and drainage capacity. Compaction grouting was used to densify foundation soils in the vicinity of existing improvements that were considered sensitive to construction-induced ground vibrations. These ground improvement techniques effectively reduced the liquefaction potential and allowed the marina improvements to be reconstructed on shallow foundations similar to the original design.