17. Track stiffness inspection method using portable track stiffness measuring device (RFWD)

A method was proposed to inspect the state of sleeper support and roadbed stiffness using a portable track stiffness measurement device (RFWD Railway Falling Weight Deflectometer) (Fig. 1 and Fig. 2). The portable RFWD is a device drops a weight onto the rail and, based on the load and the displacement, measures the track spring coefficient.
It is therefore used to evaluate track stiffness to assess the need for track repair work or track restoration after work under the roadbed.
Up until now, there was no portable machine that could be used along the rails in order to exert a load on the track to inspect track stiffness, however, measuring can be done swiftly with the highly mobile portable RFWD. Using the portable RFWD, measurements on one sleeper can be taken every 11 seconds.

Sleepers lacking the sufficient stiffness (floating sleepers) can be detected (Fig. 3), which makes it possible to check track safety after work has been carried out under the roadbed, or after track restoration work following a disaster, before allowing traffic to resume.

In addition, the track spring coefficient obtained with the portable RFWD can be used to identify locations along the roadbed that require repair, and determine the thickness that needs to be replaced as well.

Several railway operators have commenced pilot tests using the portable RFWD.