Coastal Caisson Corp.

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Drilled Shaft
Widening of I-95 over Turtle River, Brunswick, Georgia

Client:		Skanska USA Civil Southeast, Inc.
Owner:		Georgia Department of Transportation
Structural Engineer:		Post, Buckley, Schuh & Jernigan
Geotechnical Engineer:		Georgia Department of Transportation Office of Materials & Research Geotechnical Engineering Bureau
Construction Period:		September ’06 – August ‘08
Project Value:		$ 18,000,000

Scope of Work: 424 Drilled Shafts, 5’ dia. x 120’ deep average over water I-95 over the turtle River consists of two separate bridges, one Northbound and One Southbound with Three lanes each span. The Two bridges are separated by a space of approximately 50’. The Bridges span approximately 3,500’ across the Turtle River. Forty Three Bents of shafts were required consisting of mostly Four shafts per bent between the bridges, Forty Three Bents to the outside of the Northbound and Forty Three Bents outside of the South bound lane. Many of the shafts were installed less than 12” from the edge of the existing bridges. Traffic across these bridges had to continue during construction.

Because of the +- 9’ variance in tides, the diameter and lengths of the shafts and the need for precise positioning for installation specialized equipment was required. The Project consisted of  One Demonstration Shaft, Two Osterberg Load Cell Shafts and Four Hundred Twenty Four Drilled Shafts ranging in lengths up to 147’. The shafts were installed using permanent casings of approximately 50’ length and drilled under Bentonite slurry. The shafts are heavily reinforced full length using reinforcing cages consisting of 48 #11 bars. CSL testing to confirm integrity was required for all shafts. Concrete was 5,000 psi @ 28 days and is placed by concrete pump to a tremie. The shafts to the outside of the bridges are installed using a specially equipped Manitowoc 1015 Crawler Crane with a Bauer B36 Drill attachment from barges on the Turtle River. In shallower waters drilling and concreting must be coordinated with the tides. Where the water was not deep enough to float a barge, because of sand bars, the shafts are installed from trestles. The shafts between the bridges were installed using a Bauer BG28 Hydraulic Rotary Drill Rig. Many steps were involved in the installation: casing installation, drilling, slurry placement, desanding, reinforcing cage installation, slurry displacement and concreting, barge movements.