A field trial of jet-grouting in marine clay

The basement excavation of the Singapore Post Center involved extensive jet -grouting to improve the soft marine clay present within the excavation. Th e treated soil mass, with much improved strength and deformation characteri stics, was intended to act as an internal strut below the bottom of the exc avation level, reducing movements caused by the basement excavation. This p aper presents the performance of a well-instrumented field jet-grouting tri al during the construction of the building basement. Results of monitoring suggest that the jet-grouting trial caused the retaining diaphragm walls an d 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 latera l soil movements in the excavation side of the jet-grouted mass were much l arger than the corresponding lateral movements behind the wall. The results suggest that the diaphragm wall provided considerable restraint, thereby r educing the lateral movements of the soil behind the wall induced by the je t-grouting. Bending moments were induced in the diaphragm walls due to the jet-grouting work. The jet-grouting also caused some increase in the latera l earth pressure and the piezometric levels.