Page 11 - Mar-Apr19 Vol36 No7
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Needless to say, the residents were 3.7 percent which translates to a field Top of the hill - after
complaining constantly. “Extensive spread rate of 42 pounds per square yard. states that “the depth of FDR should not
repairs were made prior to using FDR,” While TDOT SP304 recommends 95 interfere with existing utilities as long as
said Warren. “Many times, we had crews percent compaction, S&ME recommend they are installed to the proper depth. The
out there making repairs after hours and that the FDR base be compacted to at only utility we hit was communications
on the weekends.” As a result, the cost to least 98 percent of the standard Proctor (i.e. cable TV) which wasn’t buried deep
make needed repairs were adding up and maximum dry density to achieve greater enough as required and given that, it
becoming very costly to the county. They strength. This level of compaction was was the cable company’s responsibility
needed a better, more permanent solution. achieved by the contractor with ease to fix the damage.” The subdivision also
during construction. contained curb and gutter, mailboxes,
Knox County knew about FDR as they and concrete driveways; these items were
had recently attended an open house Overall, Knox County was pleased with unharmed during construction.
during the FDR process on the Foot Hills their first FDR project. “It allowed us to
Parkway. They were able to witness the complete the work in a quarter of the time Knox County now has a brand new
process firsthand and learn the answers as traditional repairs and the residents road with a base strong enough to ensure
to all of their questions. Understanding of the subdivision were minimally longevity for its 1 1/5” topping of surface
the process and witnessing the results disrupted,” said Warren. A common D-mix. When asked if Knox County will
gave the county enough ammunition to concern of many counties and cities is use FDR again, Warren said “Yes, we have
get the ball rolling towards designing damage to underlying utilities. Warren several more roads and are pleased to have
the new pavement section with FDR in our tool bag.”
FDR. Geotechnical firm S&ME took
representative samples from the existing
road, which was riddled with alligator
cracking, rutting, and sections of
polished aggregate. Through mandatory
lab testing, they determined that the
FDR section needed to be 11 inches
thick. TDOT’s FDR specification, SP304,
requires an unconfined compressive
strength of 300-500 PSI in seven days.
Analysis of test results indicated that
the cement content would need to be
View online at tnpublicworks.com 11
