The Falling Weight Deflectormeter (FWD) came into being in the early 1970s. It is a pulsed dynamic sinuometer. It simulates the instantaneous impact of automobile load on the road surface and obtains the instantaneous deformation of the road surface. Its measurement results are more accurate, and the information is large.
Different bending basin radii were used for different pavement structures. Subgrade or flexible base asphalt pavement, sensor distribution within 2.5m from the load center can be used. For high grade highway with semi-rigid base asphalt pavement, the radius of influence of bending and sinking should be 3 ~ 5m. The sensor shall be arranged within a range of 3 ~ 4m from the load center and automatically measured under computer control. All test data can be displayed on the screen or printed or stored in the computer. Load, sinkage (basin), temperature of road surface, mean value of sinkage, distance between measuring points, standard deviation, coefficient of variation and data representing sinkage value and evaluation result can be output.
Road and road transport infrastructure is critical to the socio-economic advancement of a country, with the development of urban construction, the standard of road construction is getting higher and higher, therefore, Road quality inspection has became a important step in road construction, As one of the most advanced non-destructive testing equipments for pavement strength in the world, falling weight deflectometer can quickly and accurately detect and evaluate the strength of various structural layers or subgrades on the pavement.
Since the evaluation indicators and standards specified in the current specification are based on the beckman beam test, the data measured by the falling weight deflectometer must be converted into beckman beam data through comparison test before strength evaluation can be carried out. However, the transformation relationship obtained by this simple regression analysis lost a lot of information of the measured data (especially dynamic information), and did not give play to the advantage of the measured sinker data form to evaluate the bearing capacity of the pavement structure.
With the development of road traffic infrastructure construction, more and more attention has been paid to the quality of road construction. Falling Weight Deflectometer has also become an important tool that is increasingly being valued by civil engineers. The falling weight deflectometer is one of the most advanced non-destructive testing equipment for pavement strength in the world. The working principle is as follows: the falling weight deflectometer measures the dynamic deflection of the road surface and inversely calculates the rebound modulus of the road surface. It has become a hot topic in the highway industry around the world.
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.