The Tennessee Department of Transportation (TDOT) is rehabilitating a 7.66-mile corridor of I-440 from I-40 to I-24 to provide a minimum of six travel lanes (three in each direction) and replace the 30-year-old pavement. I-440 is one of the few roads in Nashville, Tennessee, which can accommodate military grade equipment due to the current overpass clearance. To maintain the necessary clearance and rehabilitate the existing pavement, several options are being considered including rubblizing the existing pavement with placement of an asphalt overlay and bridge jacking as well as rubblizing the existing pavement with removal of some thickness of the existing concrete pavement prior to asphalt overlay construction. As a result, TDOT plans to solicit design/build proposals to obtain a feasible solution that minimizes the impact to motorists.
To gather the necessary materials and geotechnical data required to support the design/build process, AEI performed a fast-track task order through our On-Call Geotechnical Contract. AEI committed to completing the project in 3.5 weeks, staffing the project with two experienced drill crews and two experienced Geotechnical Engineers. AEI’s expertise was invaluable with coordination of the required lane closures and traffic control necessary to complete the project.
The exploration plan included 74 borings on the roadway shoulders and the inside lane to avoid entrance and exit ramp closures. Four additional borings were drilled beneath the existing I-440 bridge over I-65 to provide geotechnical data for design of a rock bearing foundation system to support the piers for the bridge widening. Due to safety concerns and impacts to traffic from lane closures, TDOT stipulated that work on the interstate could only be performed Monday-Thursday from 8:00 p.m. to 5:00 a.m.
Laboratory testing was conducted in our AASHTO accredited laboratory, including moisture content, Atterberg limits, unconfined compressive strength, standard Proctor, and California Bearing Ratio (CBR) testing. Unconfined compressive strength testing was performed on select rock core and pavement core samples. The unconfined compressive strength of the rock core is a primary factor for determining the end bearing capacity of competent bedrock and has a significant role in deep foundation design. Unconfined compressive strength testing on the concrete will be used to determine the difficulty associated with removing or rubbleizing the existing pavement and will allow the design team to determine the cause of the current state of pavement deterioration. Standard Proctor and CBR testing was performed on clay soils representative of the subgrade materials encountered throughout the corridor. The CBR values will be utilized by the design/build team in pavement design to determine the required pavement cross-section for the project.
AEI delivered on the project nearly one week ahead of schedule.