Presented by:

R. Cadiz

For CE 260: Soil and Rock Testing

Non-destructive and non-intrusive testing

Widely used in pavement engineering to evaluate pavements structural condition

Its results determine optimum pavement maintenance and rehabilitation strategies

It characterizes pavement layer stiffness

Geophones

Geophone

Load Cell Load Plate

The FWD simulates an axle load by applying dynamic loads to a pavement surface

The loading system delivers a transient impulse load to the pavement surface

The vertical deformation at various distances from the loading plate are measured by a series of geophone sensors

The profile of the deflection is the deflection basin

There are usually 7 sensors and spaced 12 inches apart

Highways

Local Roads

Airport Runways

Parking Lots

A typical FWD test applies 4 different load levels at discrete locations and is completed in less than 2 minutes.

This test was standardized by ASTM in 1996 as ASTM D4694. Its revisions and updates were in 2003 and 2009.

Secure clearance from traffic control

Calibrate the FWD by conducting a 10-minute warm up test

Position loading plate over chosen location and lower the sensors to the pavement surface

Drop weights.

Multiple tests can be performed on the same location using different weight drop heights.

Measure air and pavement temperatures

Pavement modulus of each layer is determined by backcalculation

Some softwares developed:

ELMOD (Evaluation of Layer Moduli and Overlay Design)

MODULUS

Required input:

Deflection profile

Load data

Temperature corrections

Desired output:

Elastic Moduli of layer/s

Layer thicknesses

Expected (remaining) pavement life

Test large area very quickly

Run 1 test per minute

Grid pattern to get general picture

Data compiled and viewed in real-time

Entire test can be run from a laptop inside vehicle

Equipment is easy to transport

No sample recovery

Compliment with test pit sampling, coring or other methods

Geotechnics Philippines, Inc. (GPI)

Primax 1500 from Grontmij (UK & Denmark)

Texas Department of Transportation Technical Advisory: FAQ about the Falling Weight

Deflectometer

Interpretation of Falling Weight Deflectometer Data Animesh Das