Design, Construction, and Long-Term Monitoring of a Pile-Supported LNG Tank in Savannah, Georgia-Paper

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The paper documents the design, construction, testing, and ten-year monitoring of a pile foundation for a large LNG tank at Elba Island, Savannah, Georgia. The site contained up to 40 feet of soft, under-consolidated clay, a potentially liquefiable sand layer, and a competent Marl bearing stratum. The tank was supported by 1,600 driven, 18-inch-square prestressed concrete piles.<br /><br />A five-pile test program evaluated pile capacity, driving effects, and lateral behavior. Cone penetration tests before and after driving showed substantial densification: tip resistance increased by about 97% in the sand and 22% in a sand-clay layer. The densified sand was assessed as no longer susceptible to liquefaction under the design earthquake. Static, dynamic, and Statnamic tests informed final design parameters. Pile capacity increased markedly with time; one pile’s measured capacity rose 125% between initial driving and a 12-day static test. Test results supported the design approach and allowed pile lengths to be reduced by about seven feet.<br /><br />Construction revealed that driving perimeter piles first compacted the soil toward the tank’s center, making later installation increasingly difficult. The authors recommend driving from the center outward. A hydro test recorded less than 0.25 inch of settlement, but long-term monitoring showed average settlement of about 1.6 inches, mostly in the first year. The tank later rebounded as LNG loads decreased.<br /><br />The case demonstrates the value of site-specific pile testing and post-driving soil assessment. It also shows that long-term settlement monitoring is essential: short-term tests alone may not capture the foundation’s performance over time. Although the foundation performed successfully, settlement calculations remain important for large pile groups.

Keywords

pile foundation

LNG tank

driven piles

soft clay

liquefaction

cone penetration test

pile capacity

Statnamic test

settlement monitoring

Savannah Georgia