Stabilization of a Waterfront Structure

In response to severe damages that occurred due to the strong Kobe earthquake of January 1995 in Japan with a magnitude of 7.2 in Richter scale, a strategy was adopted to enhance the earthquake resistance of the infrastructures in the coastal areas by stabilizing the waterfront structures using lightweight slurry fill. The aims were to reduce the lateral pressure behind the damaged retaining structures and to reduce the risk of liquefaction by using a nonliquefiable fill material. As part of these attempts, this paper presents the case study of reconstruction of a damaged caisson-type seawall that moved 0.8 to 3.8 m in the horizontal direction and settled 1.1 to 2.5 m due to the Kobe earthquake. The backfill was comprised of dredged material obtained from seabed, mixed with air foam and portland cement. The properties of this lightweight fill are presented up to 10 months after the construction. Relationships are developed to correlate various laboratory and field tests. The restoration strategy adopted for this project represents an effective use of marine resources for construction purposes in the coastal areas.