NNSY Helical Underpinning

Portsmouth, Virginia

The Job

As part of renovation of a storage/logistics building at the Norfolk Naval Shipyard, underpinning was required due to settlement of a column footing pile cap. In addition to settlement of the pile-supported pile cap under an exterior wall, two adjacent pile caps had settled on the outside of the loading dock.

The Challenge

Due to a limited overhead environment on the interior, but high torque requirement, piles had to be installed with a large machine from the exterior only. The bottom of footing elevation was nearly 6 feet below finish floor elevation, so extensive excavation was required on the interior, as well, further complicating the installation.

The Solution

CJGeo provided a turnkey design-build package for the piles. Due to the low count, 3.0FOS was used to avoid the load testing requirement associated with 2.0FOS.

CJGeo installed four underpinning piles and four new construction piles over two days. The 3.5″, grout-filled 10-12-14-14-14 helical piles were installed to an average depth of 57 feet, at 12,000ft-lbs. A small excavator was used inside for access excavation, while the install machine reached through the demolished wall.