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Falling Weight Deflectometer

Instrument Detail

Falling Weight Deflectometer

Model              : HWD 30 KN to 240 KN
Specification :

Working Principles

FWD is being used for NDT and evaluation of load carrying capability of highways and airfield pavements. It is a trailer mounted device and is equipped with a standard 300 mm diameter rigid (base) plate and a rubberized pad to help in distributing the load evenly. Test method  allows for  a  force amplitude and  duration  approximating  the effect  of  a heavy moving wheel load and  very  accurate deflection  measurements,  especially  at  a  very  large distances  from the center of the load. The output of the FWD is in terms of pavement surface deflections for an applied load.


Falling Weight Deflectometer

Data collected from FWD can be used for determination of structural capacity of in-service pavements for analytical analysis of pavement performance, predicting layer moduli for pavement component layers, remaining life of pavements and in deciding strengthening and rehabilitation measures to be adopted for meeting the requirements.

Analyses of data are being carried out using standard software as supplied by the manufacturer. Information such as load, layer types and thicknesses, range of moduli and Poisson’s ratio etc. for different layer materials would also be needed for FWD deflection data analysis. While carrying out analyses of data, it assumes material to be homogeneous, isotropic, linear elastic, weightless and semi-infinite. The output obtained from analyses is given as under: 

  • Transient deflections radially at seven different points
  • Layer moduli (modulus of elasticity) from the basic deflection data and predefined parameters and layer thicknesses specified
  • Modulus of subgrade reaction (k-value) for concrete pavements
  • Efficacy of load transfer between the concrete slabs
  • Overlay requirement
  • Remaining life of the pavement for the traffic levels of the specified load
  • Pavement Classification Number (PCN) for the airfield pavements

User Instructions

  • The survey vehicle used to tow the equipment shall only be driven by a “TRAINED DRIVER” for safety reasons.
  • The system shall not be used for extremely bad road conditions.
  • The Institute charges depends upon location of site, length of site, no. of repetitions, no. of points per km to be collected and nature of data analysis. 

Contact Details


Delhi-Mathura Road
P.O: CRRI, New Delhi-110025
Tel.:+91-11-26848917, Fax:+91-11-26845943
Email Id: director [dot] crri [at] nic [dot] in

Instrument Usage Charges (Including GST)