7．Automatic Irregularity-Correcting Sleepers (AICS)

Automatic Irregularity-Correcting Sleepers (AICS) were developed as a preventive measure against hanging sleepers on ballasted track.
After loading tests on a full scale model track, it was verified that this method reduces track subsidence of the track structure to below 25% and of rail joints to about 50%.

Along ballasted track sections subject to deformation and areas around rail joints inter alia, which can lead to uneven track subsidence, there is a risk of hanging sleepers appearing. Subsequent violent shocks from passing loads can damage the ballast, and lead to mud pumping which can cause sudden deterioration in the state of the track.

Preventing uneven subsidence in these zones however is a problem, and so an efficient solution to prevent hanging sleepers is being sought. Consequently, the AICS was developed which automatically adjusts the height of the sleeper where ballast has subsided thereby preventing hanging sleepers (Fig.1, Fig. 2). Automatic subsidence compensatiing device (ASC device) was built into the two standard types of sleeper used, namely the Type S and the shorter Type SS models. Hanging sleepers are effectively prevented thanks to a simple mechanism, illustrated in Fig.3.

Repeated loading tests were carried out on full scale track models. Comparison of the results for cases with and without the compensation device revealed that subsidence had been reduced to below 25% on directly fastened and ballasted track with the AICS Type S (Fig.4) and to around 50% around rail joints with the AICS Type SS (Fig.5).

Fig.1 AICS (Type S)
Fig.2 AICS (Type SS)
Fig.3 Principle of the ASC device
Fig.4 Comparative subsidence of track structure boundary areas
Fig.5 Comparative subsidence around rail joints