Large Diameter Helical Piles for Refinery Expansion-Paper

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The paper describes the use of custom large-diameter helical piles to support a 2.5-mile pipe-rack expansion at Marathon Petroleum’s refinery in Garyville, Louisiana. The refinery’s limited headroom, congested access, sensitive operating equipment, and need to minimize soil spoils made conventional auger-cast and driven piles less suitable. Helical piles offered a fast, low-disturbance installation method and allowed work around existing structures.<br /><br />The design used a composite pile: a 5.5-inch steel shaft with four 24-inch helices, connected to a 16-foot-long, 13.38-inch-diameter upper casing. The piles were designed for substantial axial and lateral loads, including hurricane wind forces. To set installation requirements, the team estimated the lead section’s torque using an empirical capacity-to-torque relationship, then accounted for the upper casing’s contribution. Field installation trials measured the casing’s additional torque, and static axial compression, tension, and lateral load tests verified design capacity and torque estimates. Test deflections were consistent with predictions.<br /><br />Approximately 1,200 piles were installed using an excavator-mounted high-torque motor, despite overhead clearances as low as 10 feet and very restricted access. The contractor averaged about 15 piles per workday. Torque and depth were recorded during installation using redundant measurement systems. Some piles that were near the required torque were allowed to rest and then retorqued.<br /><br />The project demonstrated that large composite helical piles can be effective for refinery expansions with challenging construction constraints. The piles exhibited substantial “pile freeze”—increases in torque after installation—likely associated with the large casing and shaft. The authors recommend further case histories and research on settlement under operating loads and long-term corrosion resistance to support wider refinery use.

Keywords

helical piles

refinery expansion

large-diameter piles

composite pile

torque-to-capacity

axial load testing

lateral load testing

pipe-rack support

limited headroom

Marathon Petroleum