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Enhanced shear resistance of railtracks with ballast-rubber composites: a laboratory study

S.M. Johan, Siti Farhanah (2015) Enhanced shear resistance of railtracks with ballast-rubber composites: a laboratory study. Masters thesis, Universiti Tun Hussein Onn Malaysia.

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Abstract

Railway ballast, which form an integral part of rail tracks, are highly susceptible to subsistence due to both vibration transmitted by the passing trains, as well as the influence of the weathering and contamination effect. The resulting subsistence necessitates regular monitoring and maintenance, involving cost and time consuming remedial actions, such as stone-blowing and ballast renewal. It would be desirable if some measure can be taken in minimize the maintenance costs of railway tracks, consequently to optimizing the passenger comfort. This paper describes the exploratory work on ballast-rubber composites to enhanced the shear resistance of rail tracks and identify the effects of ballast exposure to the weathering and oil contamination. The rubber elements were sourced from tyre inner tubes commonly used for motorcycles, cut and shaped accordingly to produce strips, shreds and circular patch respectively and were arranged in various pre-determined configurations within the ballast layer. Granitic stones of suitable sizes were sieved and used as representative samples of typical ballasts as the tests were mainly carried out with a standard direct shear test setup, i.e. shear box measuring 60 mm x 60 mm. In order to identify the shear resistance deterioration of aggregate-rubber mixture under poor drainage conditions by soaked a batch of aggregates in water, acid and lubricant oil to create the effect from moisture and contamination for 14 days prior to mixing and testing. The direct shear test results indicated that rubber inclusion could effectively improve the shear resistance of ballasts to various degrees, though the configurations clearly played an important role in the improvement observed. Both type of rubber (i.e. new and used), show similar result due to the degradation of used rubber tube does not too extensive. The shear resistance did not rise dramatically with the rubber reinforcement. This susceptible shear strain plots indicate ductile behaviour on the aggregates-rubber composites. This is evident by the linear rise of shear stress with strain up to approximately 10 % for the control samples (CS) until it reaches a constant value. Note that all the specimens including CS are in a loose state during the testing because there were no tamping been applied on the samples. Overall the circular patch (CP) specimen was the most favourable in all conditions (dry, acid and oil). At ε = 5%, CP (D) already governed the τave with 170 kPa than the others. In addition, the friction angle for all configurations (dry, acid, oil) was in the ranged 87◦- 88◦ with the critical specific volume, vcrit was 2.160. It was followed by the ST (H), which was found to allow better deformation capability with increased ductility of the composite, while the shreds (SH) absorbed impact and reduced breakages of the ballasts. Both mechanisms contributed to the reduced overall subsistence, accompanied by an increase in the shear resistance. The inclusion of rubber elements apparently prevented the dilation of the granular material when approaching the shear failure and the reducing the settlement.

Item Type: Thesis (Masters)
Subjects: T Technology > TF Railroad engineering and operation
Depositing User: Normajihan Abd. Rahman
Date Deposited: 17 May 2016 06:50
Last Modified: 17 May 2016 06:50
URI: http://eprints.uthm.edu.my/id/eprint/8008
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