Luka Lazarević

Assessment of sleeper support conditions using micro-tremor analysis

An irregular geometry of the track can influence the safe passage of railway traffic. Therefore, maintenance activities on railways are mostly directed towards the correction of track geometry. It has been shown that unevenly supported and unsupported sleepers make major contributions to the effect of track geometry deterioration. In addition, irregular sleeper support conditions can contribute to ballast fouling, thus reducing its service life. Therefore, assessing the support conditions of the sleepers in a railway track is essential. This paper reviews methods that can be used for this purpose. Then, we propose a method for the assessment of sleeper support conditions and present results obtained in field investigations. The proposed method is based on sampling of the micro-tremor on sleepers and interpretation of obtained data. The obtained results prove that the proposed method is reliable and therefore usable in practice.

Interaction Phenomenon Between Train, Track and Bridge

The paper presents principle of track/bridge interaction in the case of temperature gradient, breaking and acceleration of railway vehicles. Influence of different bridge structures to the bridge expansion length was analysed for the purpose of expansion joint avoiding in CWR track. This would lead to the reduction of noise and vibration emission from railway traffic and maintenance activities, which is especially important in the urban environment. Additional stresses in track were considered according to the type of track and bridge deck, type of bridge bearings, as well as bridge support stiffness. Conclusion of this paper provides basic stances that could be used for the calculation of different railway bridge structures. The aim of the paper is providing the basis for improvement of the existing technical regulations in the field of railway infrastructure, as well as its harmonisation with EU regulations.

Application of seismic tomography for assessment of the railway substructure condition

This article presents results obtained in the research conducted on railway infrastructure in Serbia, which aimed at prediction of substructure condition based on the analysis of track quality. It presents the results of seismic tomography application as non-destructive procedure for assessment of railway substructure condition. Track geometry quality was assessed according to analysis of longitudinal level data, which was recorded during regular track geometry inspections. Track section for application of seismic tomography was chosen on the basis of analysed track geometry data recorded during the regular track geometry inspections in 2006, 2008, 2009, 2012, 2013 and 2014. Tomographic imaging of railway platform on Test Section enabled the creation of two-dimensional finite element model, which was used for determination of propagation speed of seismic P-waves. Seismic tomography on Test Section, which is the part of the international railway line Belgrade–Vrbnica, was performed in 2014. Obtained tomographic image was discussed and compared to track geometry data recorded during the regular track geometry inspections.

Railway/Road Level Crossing Design – Aspect of Safety and Environment

At the railway/road level crossings, two essentially different modes of transport intersect, both with a variety of vehicle performance parameters and traffic organization rules. Level crossing presents a collision zone for both transport modes from the aspect of traffic safety. Unfortunately, the probability of accidents at level crossings is still high. Railway Infrastructure Manager controls only one part of the problem (traffic management and ensuring the safety of level crossings using technical equipment and signalization). Level crossings are not always avoidable on the existing railway lines, although the preferred solution is overpass crossing. On the European railway network, level crossings occur even on the reconstructed railway lines for speeds up to 200 km/h, with the appropriate design principles and safety measures for both transport modes. This paper describes the basic design principles for the level crossings where rail vehicles reach speeds up to 200 km/h, as well as the review of the necessary measures to increase safety level.

Fly ash and slag utilization for the Serbian railway substructure

Approximately 7 million tons of fly ash and slag are produced in thermal power plants in Serbia every year, only 3% of which is used in the cement industry. About 300 million tons of the ash-slag mixture are disposed in landfills, occupying an area of approximately 1600 hectares and generating environmental issues. Fly ash from Serbian power plants has pozzolanic properties and due to low concentration of calcium compounds (less than 10% CaO), they do not have self-cementing properties. According to the ASTM C618-15, this ash is from class F. According to the European Standard EN 197-1:2011, this ash is siliceous (type V) ash. From April 2014 to May 2015, an investigation of engineering properties of fly ash and mixtures of fly ash and slag from landfill (without or with binders of cement/lime) was conducted at the Laboratory of Soil Mechanics at the Faculty of Civil Engineering of the University of Belgrade (Serbia) and at the Institute for Testing of Materials – IMS Institute in Belgrade. The laboratory test results were showed in the study ‘Utilization of fly ash and slag produced in the TPP JP EPS thermal power plants for construction of railways’. Four kinds of waste materials from Serbian power plants were laboratory tested: (a) an ash-slag mixture from landfills at the ‘Nikola Tesla A’ thermal power plant; (b) fly ash from silos in the ‘Nikola Tesla B’ thermal power plant; (c) an ash-slag mixture from landfills at the ‘Kostolac A’ and ‘Kostolac B’ thermal power plants and ‘Srednje kostolacko ostrvo’ landfill; (d) fly ash from the ‘Kostolac’ thermal power plant. The following physical and mechanical properties of ash and mixtures were investigated: grain size distribution, Atterberg limits, specific gravity, moisture-density relationship, shear strength parameters in terms of effective stresses, California Bearing Ratio (CBR), and deformation parameters. The paper presents the results of laboratory tests of the materials with and without binders, and based on the laboratory results and previous research, the paper presents possibilities of using fly ash and slag for the construction of railway substructure in the planned construction and reconstruction of railway network in Serbia. The obtained results indicate that tested fly ash and ash-slag mixture have met the technical requirements and that they have the potential to be used in railway substructure. First published online 12 December 2016