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Home » News & Event » Industry news » How does an falling weight deflectometer work

How does an falling weight deflectometer work

Views:4     Author:Site Editor     Publish Time: 2020-06-08      Origin:Site

Pavement structure and Bridges, DAMS and other civil structures are different. Its service life is relatively short. After a period of time, the road will be damaged, resulting in a decline in pavement performance. It affects the driving safety and comfort. It will also affect residents along the way. Therefore we must take appropriate repair method to restore the use of the pavement quality. The choice of suitable repair method depends on the accurate evaluation of pavement condition, among which the evaluation of pavement structure's bearing capacity is an important part of pavement condition evaluation.

Heavy Weight Deflectometer HWD

The article includes three parts

1.Falling weight deflectometer is the most advanced

2. The falling weight deflectometer’s system

3. The falling weight deflectometer’s measurement speed


1.Falling weight deflectometer is the most advanced

The Falling weight deflectometer (FWD) is the most advanced pavement deflection detection equipment in the world at present. It has the advantages of no damage, fast measurement speed and high precision, and it can well simulate the action of traffic load. The test result is the data of deflection basin, so it is widely used in the world. Its application scope mainly provides the basis for pavement maintenance management and subsequent pavement structure design.

2. The falling weight deflectometer’s system

The falling weight deflectometer uses a computer-controlled hydraulic system to lift and drop a hammer and apply a pulse load to the road, creating a pulse that simulates the impact of a moving wheel load. The size of the load can be adjusted over a considerable range by changing the lifting height of the hammer. The applied load is measured by a heavy-duty load sensor. It is transmitted to the road by a load bearing plate with a diameter of 300 mm, causing the road surface to deform. 

These deformations are measured by multiple sensors. These measured data were collected by the computer system, and the bending and settling values of each measuring point were obtained by conversion. At the same time, the "bending and settling basin diagram" was provided, which made it possible to evaluate the multi-layer pavement structure.

3. The falling weight deflectometer’s measurement speed

The falling weight deflectometer has a fast measurement speed (about 40 seconds per measurement point) and high accuracy (with a resolution of 1 micron). And it simulates the dynamic action of driving load well. In particular, the falling weight deflectometer can accurately measure the multi-point deflection, and can measure the dynamic deflection curve of road surface under various levels of load, which can accurately reflect the shape of the bending basin. The falling weight deflectometer is currently considered an ideal nondestructive testing device for road surfaces. The falling weight deflectometer not only overcomes the inherent defects of the beam deflector, but also solves the static load problem of the steady-state dynamic deflector due to its light weight. 

The advantages of falling weight deflectometer in highway testing, mainly manifested in two aspects. One is that it can according to the inverse calculation of deflection basin modulus of pavement structure layers, the pavement material properties change in the use process, provide the technical parameters. The second is falling weight deflectometer deflection basin as indicators, the overall evaluation of pavement strength, provide the basis for maintenance and management.

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