396
Proceedings of the 18
th
International Conference on Soil Mechanics and Geotechnical Engineering, Paris 2013
4.2FWD
The falling weight deflectometer, FWD works by dropping a
controlled weight and transmitted to the pavement structure
through a circular plate as shown in Figure 6. A set of geophones
(deformation sensors) mounted radially from the center of the load
plate measure the deflection in response of load pulse. The
distribution of deflection sensors are shown in Table 3.
The FWD used in the tests was model JILS-20, programmed with
a load pulse of 9000 pounds and three impact tests at every point.
The equipment had an infrared sensor to measure the temperature
of the asphalt layer.
Figure 6.FWD a) Equipment mounting b)Load cell and deflection sensors
system
Table 1. FWD - Sensor configuration
Figure 8. Typical deflection basin throughout the area, obtained using
Benkelman beam and FWD
Figure 7. a) Deflection basin -Benkelman Beam, CL 53.
a)
b)
5 EXPERIMENTAL RESULTS
5.1
Deflection basins
Figure 7 shows representative results of deflection basins
acquired in the study. The tendency of the deflection curves are
deep and
of short length, which means that the subgrade corresponds to a
poor quality soil and deficient pavement performance.It was
observed that the deflection basins obtained from the Benkelman
beam are much deeper (12 to 232 mm
-2
) than those obtained using
FWD (31,29 to 164,14 mm
-2
) giving more critical quality of the
structure, although largely this is due to static charging system
(Figure 8); that is, the analysis performed with the Benkelman
Beam is more unfavorable, being that a deeper deflection curve
indicates a deficient performance not only of the pavement
structure but also of the subgrade.
F
igure 7. b)Deflection basin-FWD, CL 53.
Figure 7c) Deflection basin-Benkelman Beam, Ring road (K0+600-
K1+150).
Figure 7d) Deflection basin-FWD, Ring road ((K0+600-K1+150)
FW
O
D Sensor number
# 9 # 1 (do) # 2 # 3 # 4 # 5 # 6 # 7 # 8
ffset fromFWD loadplate (cm)
‐20 0 20 30 45 60 90 120 150
FWD Geophones configuration
