GOETHALS BRIDGE REPLACEMENT FOUNDATION DESIGN MODIFICATIONS DUE TO FIELD CONDITIONS-Paper

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The Goethals Bridge replacement uses rock-socketed drilled shafts to support its cable-stayed towers, approach piers, and abutments. The site’s subsurface profile includes fill, glacial and marine deposits, locally liquefiable sands, and variable thicknesses of weathered Passaic Formation bedrock over competent rock. Because competent rock is relatively shallow but its elevation and quality vary, permanent steel casings were designed to extend into weathered rock, with socket lengths determined by rock quality and minimum embedment requirements.<br /><br />During construction, casing refusal frequently differed from estimated design elevations. Other challenges included obstructions during casing advancement, casings outside location tolerances, groundwater infiltration, and rock sockets drilled deeper than planned. These conditions required adjustments to both construction methods and foundation details.<br /><br />The team adopted casing rotators or oscillators where vibratory driving was ineffective and developed procedures for maintaining soil plugs and water levels during installation. Out-of-position casings were managed by shifting reinforcement within concrete-cover limits, correcting the casing position, or accommodating the remaining offset at the column connection. For casing tips above or below design elevation, engineers reassessed socket lengths and modified reinforcement as needed. Changes included adjusting tight-pitch spiral reinforcement, lowering or extending cages with mechanical couplers, and using deeper Grade 60 column bars in place of some Grade 80 shaft bars. Where structural analysis showed low demands at the shaft base, limited portions of the socket could remain unreinforced. Dry construction was considered at selected locations but abandoned when a watertight casing seal could not be achieved.<br /><br />The project demonstrates that pre-fabricated cages should include sufficient reinforcement allowances to accommodate uncertainty in casing refusal and rock elevations. Flexible construction procedures and timely engineering review can address field conditions while preserving foundation performance and design requirements.

Keywords

Goethals Bridge

rock-socketed drilled shafts

cable-stayed towers

permanent steel casings

weathered bedrock

casing refusal

rock sockets

foundation construction

reinforcement adjustment

subsurface conditions