Anti-Liquefaction Treatment by Compaction Grouting in Coastal Lagoon Deposits-Video

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Video Summary

Fanny Mocotel presented a compaction-grouting project in Saint-Barthélemy, a highly seismic Caribbean island. The site’s saturated lagoon deposits were susceptible to liquefaction, while nearby buildings and limited space ruled out options such as vibro-compaction and deep soil mixing.<br /><br />The team treated the liquefiable layer using 400 mm grout columns on a 1.4 m square grid, equivalent to a 6.4% replacement ratio. Grout was injected continuously, with withdrawal speed, energy, and grout volume monitored. The treatment aimed to densify the soil, increase the composite ground’s shear stiffness, and reduce earthquake-induced shear stresses.<br /><br />Dynamic penetrometer tests before and after treatment showed average cone resistance rising from 1.9–2.9 MPa to 4.3–7 MPa. This corresponded to a densification factor of 1.95–3.6, averaging 2.6—consistent with design predictions. The results supported compaction grouting as an effective way to mitigate liquefaction risk at this constrained site.

Keywords

compaction grouting

liquefaction mitigation

seismic soil improvement

Saint-Barthélemy

grout columns