This unique project was to install multiple 72” drilled shafts for two large bent at the river crossing. The drilled shafts were installed within the confines of a coffer cell with the requirement that they were installed without permanent casing, even though they were installed through 80 feet of water. This challenge was met by the use of a double temporary casing sequence with a sand backfill placed within the annular space of the two casings. The shafts were drilled to a depth of 145 feet below the working trestle, the shaft was poured up to an elevation just above the mud line and the inner casing was extracted leaving the sand backfill to shaft and form the drilled shaft until the concrete set and the outer casing could be removed. The shafts were stabilized with bentonite slurry below the temporary casings. There were two Osterberg Load Tests performed to verify the strengths of the sandy subsurface soils.
Owner – LaDOT
General Contractor – Gilchrist Construction