A field trial of jet-grouting in marine clay

Abstract

The basement excavation of the Singapore Post Center involved extensive jet-grouting to improve the soft marine clay present within the excavation. The treated soil mass, with much improved strength and deformation characteristics, was intended to act as an internal strut below the bottom of the excavation level, reducing movements caused by the basement excavation. This paper presents the performance of a well-instrumented field jet-grouting trial during the construction of the building basement. Results of monitoring suggest that the jet-grouting trial caused the retaining diaphragm walls and the adjacent soils immediately behind and at some distance away from the walls to move away from the jet-grouted area. The maximum free field lateral soil movements in the excavation side of the jet-grouted mass were much larger than the corresponding lateral movements behind the wall. The results suggest that the diaphragm wall provided considerable restraint, thereby reducing the lateral movements of the soil behind the wall induced by the jet-grouting. Bending moments were induced in the diaphragm walls due to the jet-grouting work. The jet-grouting also caused some increase in the lateral earth pressure and the piezometric levels.Key words: jet-grouting, ground improvement, diaphragm wall, ground movements.