Soil Improvement Through Rammed Aggregate Piers to Mitigate Liquefaction Risk in Storage Tanks-Technical Paper Upload

Technical Paper Upload

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The paper describes the design and construction of Rammed Aggregate Piers (RAPs) to improve foundation soils for four hydrocarbon storage tanks in Paraíso, Tabasco, Mexico. The site contained loose to medium-dense sandy soils, soft clay layers, and groundwater at about 3 m depth, creating significant liquefaction and settlement risks.<br /><br />A total of 980 RAPs, each 0.5 m in diameter and 12.5 m long, were installed beneath the tanks. Their displacement installation compacted surrounding soil, increased stiffness and confining stress, and provided radial drainage. Pier spacing was generally 2 m beneath tank bottoms and 1.5 m beneath perimeter ring foundations.<br /><br />Liquefaction and settlement were assessed using pre- and post-improvement Standard Penetration Test (SPT) and Cone Penetration Test (CPTu) data, alongside settlement and stability analyses. In untreated conditions, estimated post-liquefaction settlement was approximately 37–45 cm. With RAP improvement, it was reduced to about 5 cm. Post-installation testing showed increased SPT blow counts and CPT tip resistance, supporting the conclusion that the treatment improved soil density and reduced liquefaction potential.<br /><br />The installation was completed in 50 days, averaging 35 piers per day, with peak productivity of up to 575 linear metres per day. Static and pseudo-static analyses also indicated acceptable edge stability, with factors of safety of at least 1.5 and 1.1, respectively.<br /><br />The study concludes that RAPs provided an effective alternative for supporting storage tanks in potentially liquefiable soils while controlling settlement and improving ground performance.

Keywords

Rammed Aggregate Piers

RAPs

liquefaction mitigation

foundation improvement

hydrocarbon storage tanks

settlement reduction

sandy soils

soft clay

SPT CPTu

ground improvement