SR23 First Coast Expressway

Challenge:

GRL Engineers, Inc. (GRL) was contracted by the Florida Department of Transportation (FDOT) through ECS Florida, LLC in 2019 to perform dynamic pile testing and related services. GRL was the project Dynamic Testing Engineer (DTE) for the 26 bridges on 10.5 miles of new multi-lane limited access toll roadway to State Road 23, which is part of the First Coast Expressway. This $229-million project is part of the overall $1.5 billion 46 miles long project which is the result of a partnership between the FDOT and Florida’s Turnpike Enterprise. The overall project will create a new regional evacuation route, direct access connection from I-10 to I-95, and to help alleviate traffic congestion on SR 23.

Method:

Prior to construction, GRLWEAP pile drivability studies were performed for initial hammer system selection. Using a Pile Driving Analyzer^® (PDA), GRL engineers monitored pile driving onsite and provided real-time recommendations regarding hammer system performance, pile driving stresses and integrity, and driving resistance and load bearing capacity. CAPWAP and refined GRLWEAP analyses were performed to establish production pile driving criteria. Some locations utilized 100% PDA pile testing.

Challenges were encountered with pile drivability and geotechnical conditions at some of the bridge locations. Near the end of initial driving the prestressed concrete, 24-inch square piles experienced high elastic soil rebound. Although the piles encountered “practical refusal” blow counts (i.e., 20 blows/inch) the data indicated relatively low static load bearing capacity and high pile tension driving stresses. Since the situation did not allow for the development of a typical pile driving criteria, GRL and the Client decided to Implement 100% PDA testing which allowed for complete monitoring and control of pile drivability. Restrike testing was performed to assess and account for time effects (soil setup) on long-term pile load bearing capacity.

Results:

Shown below are plots of results from an initial driving and restrike tests. During the project, FDOT performed an audit; and found no deficiencies.