PANYNJ Pier Underfill
The Job
This pier underfill project is located in Hoboken, New Jersey, at a facility owned by the Port Authority of New York & New Jersey. The Authority leases the facility to a marine contractor, who is responsible for maintaining it. As part of this, the tenant had to install a new combiwall along roughly 2/3 the length of the pier, in total about 1100 linear feet. After the wall was in place, the contractor had to fill under the pier and behind the wall with tremie fill that would minimize lateral and axial loads.
CJGeo dry batch cellular grout plant onsite.
The Challenge
To minimize lateral loads on the wall during installation, and axial loads on the underlying soft soils, CJGeo proposed 75lb/cuft CJFill-Under Water. At 75lb/cuft, the proposed mix is dense enough to not mix with water during tremie placements, but only about half the density of traditional flowable fill. This reduced density minimizes axial and lateral loads during installation, and long term.
A second challenge was monitoring grout movement below the structure. The voids extended approximately 20 feet behind the wall. CJGeo proposed sonic drilling to install 4″ casings for monitoring grout movement during the filling operation.
The Solution
CJGeo mobilized a sonic drilling crew to the site, who drilled approximately 30 holes through mixed fill and the underlying wooden deck over three shifts onsite. Each hole was left cased with 4″ PVC to facilitate monitoring of the fill operation. After completion of the drilling, CJGeo mobilized a dry batch cellular concrete operation to batch and generate roughly 6,000 cubic yards of 75lb/cuft CJFill-Under Water.
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