Acta Scientiarum Polonorum

The sleepers in a railway track transfer vertical, transverse and longitudinal loads to the track ballast and subgrade.
The sleepers allow for keeping the distance between the rails constant. The thickness of ballast should
be between 16 and 35 cm depending on the design standard of the track, and it should be densified where the
ballast supports the sleeper.
The exploitation causes contamination of the ballast, crushing the material under cyclic dynamic loads, which
results in the settlement of sleepers. Consequently, the thickness of ballast is not sufficient and the effects
such as longitudinal unevenness of rails and track twist appear. Those effects have negative impact on the
comfort and travel safety, in the extreme cases leading to the derailment.
The parameters like ballast thickness, degree of its contamination, its density and sleepers’ settlement are
difficult to measure so that they can be considered as ‘fuzzy’. Therefore, the fuzzy sets and transfer functions
are used to determine those parameters. The cause and effect relationships and their impact on the reliability
of the system will be analyzed in the fuzzy sets’ domain. Special attention will be paid to use this concept
in forecasting the track tamping to enhance the interaction of the track surface with the soil ground and to
increase safety.