North American Stainless (NAS) used an unloading dock constructed in the mid-1990s on a site along the Ohio River to facilitate incoming raw materials. The dock was constructed with anchored Z section sheet pile ranging from 32 feet to 70 feet long. Anchor rods located at 19 to 25 feet below the top of the sheet pile wall were anchored to a sheet pile deadman system and connected to the upstream and downstream walls. Backfill material consisting of fine to medium grained river sand was placed behind the wall to construct the dock.
NAS experienced a major dock failure along the Ohio River when flood waters receded, causing high water pressures behind the sheet piling that snapped the steel tie-backs along a 100-ft length of the dock, causing the sheet piling to lean significantly toward the river and thus causing the concrete dock slab behind the sheeting to collapse vertically as much as 10 feet.
AEI determined scour was the likely factor in the failure and developed a repair plan to prevent such a failure from occurring in the future. For the 360-ft portion of the dock where the tie-backs had not failed but yet had elongated enough so that the sheet piling was visibly leaning toward the river, AEI developed a design to add a higher row of tie-backs anchored to a concrete dead man along with a drainage system behind the sheet piling to quickly relieve water pressures when high water during flood stage quickly recedes. A plan was also developed to stabilize the failed 100-ft portion of the wall as opposed to fixing it immediately since the 360-ft portion that was repaired was enough for NAS to continue normal barge unloading operations.