The historic Huey P. Long Bridge in New Orleans is a through truss which was to be widened with an additional truss on either side of the existing structure. The foundations at this site presented special challenges due to the requirements for very deep drilled shafts in the Mississippi River beneath the existing bridge structure. Malcolm installed drilled shafts to depths of 200 feet into alluvial soils using a rotator system with full-length segmental casing, and base grouted to improve axial resistance.
This method was accepted as a value-engineered alternative to the original concept of open-hole drilling with mineral slurry support. Full casing support eliminated the risk of a borehole collapse and potential contamination of the sidewall thereby avoiding any adverse effects on side resistance. The drilling depth, the loose granular nature of the soils, buried willow mats, and other obstructions presented a concern that the rotator casing could become stuck due to excessive friction build up during the time required to set the reinforcement and complete the splices necessitated by the restricted headroom. Malcolm’s experienced operators were able to successfully accomplish this work with careful, slow, and steady drilling while maintaining a soil plug and fluid level inside the case more than the groundwater head.