Around Moretrench: Drilling Down in Florida

May 18, 2015

Making sure your next project  gets off to the right start is what Moretrench is all about.  No matter the requirement –groundwater control, excavation support, settlement control,  ground improvement, foundation systems – we have the tools, the resources,  and the geotechnical expertise to get the job done.  And for Florida DOT’s Overland Bridge Project,  that expertise came in the form of large-diameter drilled shafts.

The Overland Bridge Project is the largest transportation design-build in the history of Jacksonville, FL. Extending south of the Fuller Warren Bridge that carries I-95 over the St John’s River, the project includes replacement of a series of existing overpasses, widening of both the Fuller Warren Bridge and I-95, and replacement of an existing bridge spanning  Florida East Coast (FEC) railroad tracks.  The $277M project is being accomplished in phases over the next  two  years to allow staged demolition and re-building in order to maintain adequate traffic flow along the I-95 corridor. Moretrench’s Orlando office was the successful bidder for the recently completed Phase 1 drilled shaft bridge foundations,  with further work contracted for Phases 2 and 3.

Construction at the Fuller Warren Bridge involves widening of the south end of the bridge to provide an additional south bound lane adjacent to a two-lane exit ramp.  “There were a number of challenges to the shaft installation here,” notes Assistant Branch Manager Kris Stenberg.  “It was a particularly tight site. We were drilling between themain span and the exit ramp. Four shafts had to be installed from a trestle over the river, so we had to ensure that there was no environmental impact to the water during this part of the work.”

The bridge remained open throughout shaft installation. Prior to production work, three sacrificial shafts were constructed at +/- 700-foot intervals in similar soils along the corridor where production shafts were installed, and load tested to verify design assumptions. Twelve,  60-inch diameter land-based shafts and the four, 72-inch over-water shafts were drilled to depths varying between 55 and 80 feet and terminated in competent marl.  All shafts were cased through the upper sands, with stability of the underlying limestone maintained with bentonite slurry.

At the FEC railroad bridge site, two bridge spans remained open. With work accomplished adjacent to active roadways within an urban environment, a heightened level of safety was maintained at all times.  Ten, 60-inch diameter and five, 42-inch diameter shafts were installed to depths of between 55 and 70 feet using the same construction method as the Fuller Warren Bridge shafts.  Moretrench will return to the FEC bridge during Phases 2 and 3 to install a further 21, 60-inch diameter and 6, 42-inch diameter shafts.