Abstract:
As part of the construction of a real estate project located in the French overseas collectivity of SaintBarthé lemy (strong seismic hazard, magnitude of 7.5), Menard has executed an anti-liquefaction treatment on the whole project. In the vicinity of the seafront, the site lies on an old lagoon area that is now filled. The latter appears on a non-negligible soil thickness. Solutions of deep foundations or generating vibrations (vibrocompaction, stone columns) were not appropriate considering the small size of the site and the presence of buildings at the edge of property. Menard has thus suggested a solution of soil improvement by Compaction Grouting. The primary objective of this technique is to densify laterally the ground by controlled pumping of a cement mortar under pressure. The Compaction Grouting enables to mitigate the risk of liquefaction in the deposits of clayey sand lagoon trough 3 main effects: review of the soil category, soil densification and shear stress reduction. This article focuses on the densification effect. A dynamic penetrometer test campaign has been performed before and after treatment out to justify the increase in the safety level by the densification effect (theoretically assessed in the design) with regard to liquefaction. Keywords: Ground improvement, compaction grouting, liquefaction, densification, dynamic penetrometer