UTILIZING A PRESSURE PAPER FOR THE DETERMINATION OF CONTACT PARAMETERS BETWEEN AGGREGATE AND A RAILWAY SLEEPER.

This paper focuses on the transmission of loads imposed by passing trains to railway aggregates utilizing a pressure paper method, which enables the quantification of contact parameters on the interface between the railway sleeper bottom and railway ballast. Modern railway ballasted tracks consist of railway sleepers which fulfil especially the functions related to holding rail strings in the gage and inclination, enable fastening system installation, transmit forces and finally spread wheel loads on the ballast made typically of natural crushed stone. The contact parameters between the sleeper soffit and crushed stone influence the lateral track stability and the ballast wear and thus the aggregates service life. The main parameters are the indentation of grains on the sleeper surface and the contact area and the pressure between the sleeper and the grains. The load distribution transmitted to the ballast bed relies on the sleeper bending stiffness depending on the sleeper structure and applied material. Utilizing pre-stressed concrete, impregnated wood or polymers representing the state of the art among the materials used in the production of railway sleepers, the sleeper stiffness varies as well as the sleeper surface hardness. In this research, ultrathin polyester-based pressure paper with microcapsules developing a red colour agent when applying specific pressure was used between the sleeper soffit and the ballast bed to determine the contact parameters. The laboratory test focused on the most loaded part of the sleeper, the sleeper rail seat. The test was conducted on samples prepared as sleeper sections. The static force reflecting the traffic resembling the load acting on the sleeper samples was calculated using typical linear formulas. A standardized geometric ballast plate made of steel was used for modelling the track bed aggregates at the rail seat. A wide selection of samples prepared from sleepers of a different material and structural basis showed different performances from the perspective of contact parameters on the sleepers’ soffit. The performed test provided enough data for developing a follow-up, full-scale laboratory test with the whole sleeper body in a laboratory ballast box filled with aggregates. [ABSTRACT FROM AUTHOR]