Innovative design & construction to toe-in sheet piling in bedrock

Authorship

Moustafa A. Gouda, Fellow in the American Society of Civil Engineers (F.ASCE), D. Matthew Stuart, F.ASCE, SECB; William F. Mercurio, CMX, Manalapan, NJ

Publication

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The innovative design and reconstruction of a toe-in steel sheet pile bulkhead was installed for the Joint Meetings of Essex and Union (JMEUC) Counties outfall structure bulkhead. The site is located along the Arthur Kill in the City of Elizabeth, UnionCounty, New Jersey.

The site originally contained two existing steel sheet pile bulkheads, approximately 70 feet total in horizontal extent, located on each side of a cast in place concrete outfall chamber owned by JMEUC. The original steel sheet pile bulkheads were constructed circa 1933 and had suffered significant deterioration, which was allowing the loss of retained material from behind the wall.

The current design and installation uses A 690 Marine Grade steel because of its greater resistance to seawater corrosion. Innovative concepts were incorporated into the design and construction to minimise costs and provide stable support for the steel sheet pile bulkhead.

Since the tieback reaction force was not orthogonal to the bulkhead it was necessary to resolve the longitudinal anchor resultant component that was parallel to the bulkhead via tension and compression forces in the upper concrete waler cap. Five foot six inch long stainless steel shear pins ASTM A304 were installed in holes drilled after the sheet piling was installed and before the tie back anchors were stressed.

Site location and project description

The project site is located along the Arthur Kill in the City of Elizabeth, Union County, New Jersey. The site is bordered by the Arthur Kill to the east, South Front Street and the JMEUC Wastewater Treatment Plant to the west, the Bourne Chemical Facility to the north, and Highway 287 to the south.

The site contains two existing steel sheet piling bulkheads, totaling approximately 70 feet in length, located at each side of a concrete outfall chamber owned by JMEUC.

The piling includes protective fender supports. The outfall structure discharges into the Arthur Kill. The steel bulkheads were constructed circa 1933 and have suffered significant deterioration resulting in the loss of material from behind the wall. Site information was derived from a report by Boswell Underwater Engineering, 2001, as well as our site reconnaissance.

Based on the available topographic information, the top of the sheet piling bulkhead elevation is 8.4 feet. The riverbed (mudline) elevations range from 6.0 to – 20.8 feet.

The extent of the bulkhead into the ground is not known. All elevations in this paper are in feet and are referenced to the project’s topographical datum.

The 2001 investigation was performed to determine the thickness and general condition of the steel sheet piling that form the bulkhead along the Arthur Kill east of the Wastewater Treatment Plant. The bulkhead is the waterside retaining structure for the plant outlet chamber.

The condition of the existing steel sheet piling was found to be poor. In the area above Mean High Water, the sheet piling was found to have heavy to severe corrosion. The corrosion was in the form of heavy pitting and perforated steel.

Within the tidal zone, the steel sheet piling was found to have heavy to severe corrosion in the form of heavily pitted steel as well as large holes six to seven feet high for the full width of the steel sheet piling.

Below Mean Low Water the steel sheet piling had heavy corrosion with intermittent pitting uniformly distributed over 100 per cent of the steel sheet piling surface area as well as large holes.

In the areas where the steel sheet piling was in contact with the earth fill, large quantities of the fill material had disappeared and the bulkhead was not providing adequate support for the remaining soil.

The two concrete outlet chambers were in satisfactory condition and no repair was necessary. CMX was contracted to design and construction manage the steel sheet piling replacement.

Geology

According to Jumikis, 1975, the original ground surface of the site has been covered by varying depths of fill material. The fill was placed to cover unsatisfactory soil conditions or to raise the ground surface above the water level.

The underlying soil consists of glacial ground moraine, composed of non-residual, unstratified materials, deposited during Wisconsin glaciation.

Glacial ground moraine is un-assorted and heterogeneous, intermixed soil fractions, which range from clay sizes to gravel, cobbles and boulders. Silts predominate, but intermingled deposits of stratified sands are present.

The bulk of the materials are composed of particles derived from nearby red shales and sandstones.

The underlying formation is red shale with occasional beds of red sandstone.

The red Brunswick shale formation is a sedimentary rock of Triassic age formed by consolidation of silt and clay.

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