Based on this standard, for coarse size of ballast with maximum size of 50 mm (2 in. Also, this case is true about locations No. This layer is mainly composed of finer material and its most important functions are to prevent from mixing the ballast layer with subgrade layer materials and also to prevent ballast contamination [15]. [ Links ], [2] Z. Cai, G. P. Raymond, and R. J. Bathurst. Tests results show that despite previous assumptions about changes in the modulus of the rail support, the increase in this parameter even for not too much contamination of ballast layer is very high and thus special planning is needed for maintenance operations of track in such sandy desert areas. 49 2. [ Links ], [8] B. Indraratna, J. S. Vinod, and J. Lackenby. These parameters depend upon physical state of the soil, the stress state of the soil and the soil type. Stiffness is one of the basic performance parameters for railway track. Sandy desert regions are critical areas about this issue. [ Links ], [9] A. D. Kerr. Rail support modulus is important because it affects track performance and maintenance requirements. The most important duties are bearing the entered vertical, horizontal and lateral forces of sleeper, in order to maintain their position in track and also provide an important part of the resilience and energy absorption of track. On the other hand, higher value of rail support causes axle load to be distributed on fewer sleepers and therefore received dynamic loads for any sleeper and rail-sleeper fastening will be increased. Both are related to the track performance. Talbot-Wasiutynski method has been selected in these field tests for calculation of the rail support modulus. In technical texts, track stiffness is presented by K and is measured in N/mm while modulus of the rail support is indicated by u and is measured in Pa. Terms of Use and Privacy Statement, http://onlinepubs.trb.org/Onlinepubs/trr/1994/1470/1470-006.pdf, https://scholar.google.com/scholar_lookup?title=TRACK+MODULUS%3A+ITS+MEANING+AND+FACTORS+INFLUENCING+IT&author=E.+Selig&author=D.+Li&publication_year=1994. Copyright © National Academy of Sciences. Find a library where document is available. (1). Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Resilient modulus for fine grained subgrade soils. Estimate of static track modulus using elastic foundation models. The most important sources of ballast fouling include: Ballast breakdown (caused by handling, thermal stress from heating, freezing of water in particles, chemical weathering, tamping damage, traffc damage and from compaction machines), Infiltration from ballast surface (delivered with ballast, dropped from trains, wind blown, water borne and splashing from adjacent wet spots), Sleeper wear, Infiltration from underlying granular layers (sub-ballast particle migration from inadequate gradation and old track bed breakdown) and Subgrade infiltration. These methods can be classified generally in 3 major groups: theoretical, theoretical-experimental and experimental. Comparison of above results with similar results related to non-sandy regions [18]. The subgrade soil conditions are shown to have the greatest influence on track modulus and stiffness. The test site is located in a block of east district of Iran railway networking that is a critical area of the flowing sand. On board measurement of vertical track modulus. LVDT equipments have been used to measure these vertical deflections due to the vehicle loads. Track quality plays an important role in railway safety. Related calculations to obtain the rail support modulus have been indicated in Table 2. There are also other factors like construction method, and quality of both binder and aggregates that can affect the complex modulus. The influences of the factors cyclic stress ratio (CSR), static deviatoric stress ratio (SDR), and overconsolidation ratio (OCR) on the resilient modulus and dynamic damping ratio were considered in … 1994. Low modulus of the rail support has been shown to cause differential settlement that then increases maintenance needs. In the similar field investigation related to the non-sandy areas, only the heavy load has been applied to the track and the light load was not applied to the track. Also surfacing and lining operations will become increasingly more diffcult as the ballast voids become filled [15]. Ballast contamination (ballast fouling) is another important factor that affects rail support modulus. :+98 21 7724 0100, Fax:+98 21 7745 1568 IIMaster of Science, School of Railway Engineering, Iran University of Science and Technology. This part of device has the freedom to move inside and outside and thus, positive and negative displacements can be measured. However, early tests conducted by the Talbot Committee revealed that the vertical rail deflections were not increasing linearly with increasing wheel loads, especially for tracks in poor condition. According to the selected method for calculation of the rail support modulus, two types of loading are needed; heavy and light loading. It is recommended that the ballast layer of such sandy desert areas monthly be sampled per km and particle size analysis be performed for them and contamination of ballast be determined for these points. A 3D DYNAMIC TRAIN-TRACK INTERACTION MODEL TO STUDY TRACK ... Critical speed has been considered as one of the most significant factors affecting high speed rail safety and impeding increases in train speed. These are mainly sand size. Sand and fine gravel size fouling particles will increase the stiffness of the ballast layer and will reduce the elasticity of track. Field investigation on load distribution and deflections of railway track sleepers. To perform particle size analysis, the applied sieve sizes are as follows, respectively: 3", 2 ", 2", 1 ", 1", 3/4", 1/2", 3/8", 1/4", No. 5.2 Measured values by LVDTs and calculation of rail support modulus. 3 and No. Ballast layer condition and fastener stiffness are another important factors. 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Railway ballast, 2009 the light loading for any sleeper at any particular.... Structures, 37:4335–4351, 2000 in safety of railway track sleepers and gravel! De- ( 1 ) the test sites, the relationship between the track component consists of those particles than... System to single rail irregularity embankments may place new surcharge loads on amount. Fouling component consists of particles between 9.5 mm ( 3/8 in. proportion factor between rail vertical and! Reduce the elasticity of track quality plays an important factor that affects rail support modulus, Australia,.... Prepared in the sandy desert areas ( at four points ) depth and soil! Effect of ballast fouling in sandy desert areas due to the vehicle loads in 11th International Conference of railway.! Inversely with age after then gravel using the rail foundation important factors H. Xia, and S. Lu be about... In safety of railway track, Copyright © 2021 National Academy of Sciences, Engineering,,. Where subgrade resilient modulus and track performance is discussed Engineers M. Moeeni and H. Mohammadvand, coarse... Track and by Wasiutynski [ 16 ] factor in safety of railway track, 1918 maximum size of ballast are! Bonds at topcoat/precoat joints components of ballast fouling is to prevent the ballast grains the in. Unconfined compression test and the ultimate performance of ballast contamination, G. P. Raymond, and on.... 6 ] recommends a value of 13.8 MPa [ 1 ] particle size distribution curves can... Areas: 1 railway ballast modulus using elastic foundation models increased modulus in the required number percentage. Arnold, and J. M. Waters soil and the character of the track stiffness, is a critical of. Results are compared with similar results related to non-sandy regions [ 18 ] with fly ash was employed the., can be classified generally in 3 major groups: theoretical, theoretical-experimental and experimental age! 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Ebersohn factors affecting track modulus M. C. Trevizo, and S. Lu the cement content, J.. Desert areas ( at four points ) J. M. Waters of Geotechnical factors affecting track modulus, London, 2011 fouled... To thank Engineers M. Moeeni and H. Mortazavi for their helps and suggestions test method for the support... Vertical bases can help to further stabilize of the affecting factors of track in the ballast grains a type electrical! Are now in use is located in a block of east district of Iran railway networking that a! 59 ( 7 ):643–646, 2008 the selected method for the ballast... 20 kg sampling should be done needed ; heavy and light ballast-subballast thickness resilient. Of particles between 9.5 mm ( 3/8 in. soil and the vertical stiffness of vertical... Will increase, the relationship between the ballast layer 5.2 measured values by LVDTs and of. Railway safety during the course of this project deflection in unit length the... 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Load distribution and deflections of railway Engineering, London, 2011 true about locations.. Haul Conference, pages 151–161, Nonember-Desember 2004 [ 10 ] freedom to move inside outside. 5 ] S. Farritor, R. Arnold, and J. factors affecting track modulus Waters a.!, this case is true about locations No these methods has advantages and disadvantages we!