Falling weight deflectometer measurement

Falling weight deflectometer measurement (FWD), the passage of a heavy wheel load is simulated by applying dynamic load to the surface. The results from a FWD test can be used in bearing capacity analyses and controls, pavement lifetime calculations and for design of pavement rehabilitation of roads and other trafficked surfaces.

When loading, the response/deflection of the surface is measured in the load centre as well as at a number of intervals up to 150 cm from the load centre. Using the test results, the stiffness of the pavement structure and its layers can be analyzed.

The test results reveal good and bad sections regarding bearing capacity along the measured distance. The test results are also used for different types of bearing capacity analyzes of pavement structures on road and airfields such as Pavement Classification Number (PCN) of airfields and analyzes of concrete roads, docksides and other kinds or industrial surface areas that are exposed to heavy loads.

VTI has two automatic Falling weight deflectometers. One of these is manufactured by KUAB and is used for loads from 15 kN up to 65 kN – mainly on asphalt roads but also on gravel roads and unbound superstructure layers during the construction phase. The second deflectometer is a heavy FWD that is used for measuring airport runways, concrete roads and similar surfaces.

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