Abstract

BROEKMAN, A  and  GRABE, P J. Measurement of probabilistic ballast particle dynamics using Kli-Pi. J. S. Afr. Inst. Civ. Eng. [online]. 2021, vol.63, n.1, pp.11-23. ISSN 2309-8775.  http://dx.doi.org/10.17159/2309-8775/2021/v63n1a2.

At first glance the operational performance of ballast appears trivial in its simplicity. However, various mechanisms affect the performance of the ballast both on a macroscopic scale and discrete (mesoscale) particle level. The importance of experimental studies to establish the influence of the granular fabric has been highlighted repeatedly by other researchers. This paper describes a method by which quantitative metrics and statistics can describe the probabilistic response of railway ballast. The measurements were obtained with the installation of a set of customised wireless inertial measurement unit (IMU), referred to as Kli-Pi, in the granular layers of a heavy-haul railway line located in South Africa. The results indicate a complex interaction of displacement and rotation, in all three spatial dimensions. The high-frequency measurements provided approximations of the particle's kinetic and potential energy (mechanical work) in addition to the indirect quantification of changes to the granular fabric. Finally, the descriptive statistics of the mechanical work provided an indirect measure of the confinement and coordination number of the particle, together with supporting evidence of the underlying probabilistic, instead of the expected deterministic response. These results strongly agree with the findings of existing literature that has, to date, been confined to theoretical study.

Keywords : probabilistic ballast particle dynamics; smart ballast instrumentation; Kli-Pi; granular fabric quantification; mesoscale ballast dynamics; impact loading.

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