Anti-Liquefaction Treatment by Compaction Grouting in Coastal Lagoon Deposits-PPT Presentation

PPT Presentation

Pdf Summary

The presentation describes liquefaction mitigation for a real-estate development on coastal lagoon deposits in a strong seismic hazard zone. The site’s groundwater lies 0.8–1.8 m below ground level. Beneath any man-made fill, the soil profile includes liquefiable clayey sand lagoon deposits extending to approximately 5.6–7.2 m, underlain by weathered bedrock and microdiorite.<br /><br />Compaction grouting was selected to improve the lagoon soils. The design uses 400 mm-diameter columns on a 1.4 m square grid, giving a replacement ratio of 6.4%. The treatment aims to densify the soil, reduce the shear stress it experiences, and improve its seismic soil classification. The anticipated improvement was from soil class E to class C, reducing the calculated maximum horizontal acceleration from 0.42 g to 0.345 g.<br /><br />Predicted densification was assessed using established correlations, with estimated relative density increasing from an initial 32–51% to 58–76%. Six dynamic penetrometer tests were conducted before and after treatment. The resulting increase in cone resistance confirmed soil densification, and the measured improvement was consistent with predictions.<br /><br />The project concludes that compaction grouting can mitigate liquefaction risk in lagoon deposits through soil densification, reduced shear stress, and improved soil classification.

Keywords

liquefaction mitigation

compaction grouting

lagoon deposits

seismic hazard

groundwater

soil densification

relative density

dynamic penetrometer

soil classification

cone resistance