This paper outlines the mitigation measures performed to address the liquefaction concerns of the foundation ground underneath a manufacturing plant site in Nagoya, Japan. Initially, a detailed soil investigation was performed and the liquefaction potential for the specified ground motion was evaluated. Considering the various site restrictions, compaction grouting was chosen as the most practical method to strengthen the foundation ground. Test acceptance criteria based on the relation between target N-values and fines content were established. In addition, dynamic soil-structure interaction analysis was performed to confirm the adequacy of soil improvement. This paper discusses the design and lessons learned from the grouting process and highlights the merits of compaction grouting as a practical method of ground improvement for seismic risk mitigation under existing structures.
Buildings and other civil engineering structures constructed over loose saturated sandy deposits are highly susceptible to liquefaction-induced damage during major earthquakes. To mitigate such damage, remedial measures should be implemented around or under existing structures without adversely affecting them. In selecting the appropriate remedial measures for constrained and/or developed sites, various factors should be considered. These include effectiveness of improvement, required areas and depth of improvement, effects on surrounding environment, cost and ease of execution, and level of desired improvement, among others. In some instances, two or more remedial measures are combined t o produce the desired results. Because of its versatility and economy in improving ground beneath and around existing facilities, compaction grouting is gaining interest among engineers. Originating in the U.S., compaction grouting technology has been implemented in Japan only in the last ten years. Although initially developed for settle-ment control and re-leveling, the technology has been used to solve a number of geotechnical problems, among them the treatment of liquefiable soils.
