Mitigation of Seismic Liquefaction Geohazard Associated to Sea-Level Rise Through Compacted Granular Columns: A Pilot Case Study

Sea-level rise (SLR) due to climate change causes an increasing seismic liquefaction risk to coastal structures and infrastructures. This study investigates the effectiveness of compacted granular columns, specifically the rammed aggregate piers (RAPs), as a sustainable ground improvement technique to mitigate liquefaction risk in future SLR scenarios. GranularColumns v.1.2 software was specifically developed to support the design of RAPs under both static and seismic loading conditions. The software was used to evaluate liquefaction risk and propose mitigation solutions for a coastal site at Palizzi Marina district (Italy), where geotechnical investigations identified potentially liquefiable silty sand layers at shallow depths. Liquefaction potential was assessed using the liquefaction potential index (LPI), considering different earthquake scenarios, as well as three future projections of SLR up to the year 2100. The results show that the liquefaction geohazard is currently low, but would increase significantly due to SLR, with LPI values equal to 14.6 (high risk) under the most severe seismic and climatic scenarios. On the other hand, when RAPs are properly designed, a reduction of LPI to acceptable levels (LPI<5) was observed for all considered climate and seismic conditions.