Time
domain reflectometer rods were installed in various locations in
the subgrade and in the concrete slabs. The purpose of these
gages is to measure moisture content of the medium in which they
are installed. This process is indirect and gages must
individually be calibrated. The method of operation is as
follows: a pulse is sent to the gage. The reflection of the
pulse is then obained. Analysis of the pulse reflection is made
and provides a measure of the Dielectric "constant"
value of the medium. Calibration equations developed in the
laboratory are then used to obtain moisture content values from
the dielectric values. For all gages located in the subgrade the
Topps and Davis equation is used. For other gages the FAA is
developing calibration equations.
Below
is a plan view of the instrumented pavement section located on
Runway 34R/16L at DIA. For detailed information on a specific
set of sensors, click on the corresponding link below on the
right.
