This stress-strain relationship is known as Hooke’s Law, and in this region, the slope of the stress-strain curve is referred to as the modulus of elasticity (aka Young’s modulus), denoted E. The modulus of elasticity is essentially a measure of stiffness and is one of the factors used to calculate a material’s deflection under load. material returns to the dimension it had before the load- ing, it is elastic deformation. Therefore, more accurate planning to eliminate the ballast layer pollution and other maintenance operations are necessary in such areas, because increasing of this modulus causes more dynamic loads to the sleeper and thus more and faster damage of sleeper is expected in such regions. As the light loading, load of 4 tons from a 2-axle draisine was applied to the track (Fig. Effect of low track modulus on track performance. In 11th International Conference of Railway Engineering, London, 2011. Factors affecting absorption: A. The locomotive was run over the rail with the speed of 15 km/hr and therefore dynamic load coeffcient considered to be equal to 1.07 and therefore the axle load is equal to 19.8 tons. As can be seen in the Fig. The effect of ballast fouling is to prevent the ballast from fulfilling its functions. Fig. Another parameter, track stiffness, is a measure of the vertical stiffness of the entire track structure. 3). In loudspeaker systems, the value of the damping factor between a particular loudspeaker and a particular amplifier describes the ability of the amplifier to control undesirable movement of the speaker cone near the resonant frequency of the speaker system. 1470, Railroad Research Issues. AN INVESTIGATION INTO DYNAMIC MODULUS OF HOT-MIX ASPHALT AND IT’S CONTRIBUTING FACTORS Mary Marjorie Robbins Master of Science, May 9, 2009 (B.S.C.E., University of Toledo, 2005) 174 Typed Pages Directed by David H. Timm One of the key elements of mechanistic-empirical (M-E) flexible pavement Increasing the width of ballast shoulder and or increasing fastener stiffness will increase rail support modulus [11]. The efficient and accurate stiffness measurement has been considered as the foundation for further development of railway engineering, and therefore has great theoretical and practical significance. During construction and use, several problems arise for repair and maintenance of track, locomotives and wagons that pass the route of desert sands. A study has been conducted to investigate the mechanical properties of cement-mixed gravel using the unconfined compression test and the tensile test. 10, No. volume 35, 1933. In order to provide a basis for assessing and modifying track performance, the definitions of track modulus and track stiffness are reviewed, and four methods of determining track modulus or track stiffness are discussed. These amounts show that the influence of sandy fine grains between ballast aggregates makes the ballast layer stiffness begins to rise and thus the rail support modulus increases in sandy desert areas. Explanation. [ Links ], [2] Z. Cai, G. P. Raymond, and R. J. Bathurst. In this paper the results of a field investigation about the ballast contamination percentage and the values of the rail support modulus in sandy desert areas presented. Drug solubility and dissolution rate b. These results are presented as follows and they are compared with similar results related to non-sandy region that are obtained from another similar field investigation. In addition to increased modulus in track, numerous other problems are produced in these areas. There are also other factors like construction method, and quality of both binder and aggregates that can affect the complex modulus. Understanding and modeling drainage of railway ballast. 6). Field investigation on load distribution and deflections of railway track sleepers. 8 shows the particle size distribution curves for all selected locations. 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 … Track stiffness is defined as proportion factor between rail vertical displacement and vertical contact pressure between rail base and track foundation. 2 THE METHODS FOR MEASUREMENT OF THE RAIL SUPPORT MODULUS. Copyright © National Academy of Sciences. c136-96 a. 20 and No. According to the obtained data from expressed field measurements, useful results are achievable about the rail support modulus in the sandy desert regions. Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates. It is better to use ballast cleaning operation only if the interval between two rehabilitation operations is less than three mouths, because the serious damage will not be entered to other components of the track in this short interval. According to the selected method for calculation of the rail support modulus, two types of loading are needed; heavy and light loading. In sandy desert regions, ballast layer takes away from the granular behavior, because ballast fouling is increasing and thus track elasticity is reducing. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. 7). 3.1 Ballast fouling in sandy desert areas. Physicochemical properties of drug a. Ballast layer is a layer of broken stone materials with 20 to 60 mm in diameter that sleepers and rails are placed on it. Resilient modulus for fine grained subgrade soils. 1 shows the summary of this classification. "recherches experimentales sur les déformations elastiques et le travail de la superstructure des chemins de fer" (experimantal research on the elastic deformations and stresses in a railroad track, in french). Particle size and effective surface area c. Polymorphism and amorphism d. Pseudopolymorphism(hydrates or solvates) e. Salt form of the drug f. Lipophilicity of the drug g. Drug stability h. that are the fouling components of ballast, are presented in Table 1. In each four test sites, the ballast was sampled and particle size analysis has been taken on these samples. AREA BULLETION 675. All rights reserved. [ Links ], [5] S. Crawford, M. Murray, and J. Powell. Theoretical methods are questionable about validity and on the other hand, generally, there are many problems with experimental methods about their field tests and they lead to very high time and costs consuming. Of the factors considered, those with the most influence on the track modulus are the ballast depth and the fastener stiffness. First Progress Report, Proceedings AREA. Both low and large modulus is undesirable. These data have been recorded for all test locations and for both heavy and light loadings. Sandy desert areas are critical regions about the contamination of ballast. dynamic deflection and the ultimate performance of the track. [ Links ], [18] J. 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. Stiffness is one of the basic performance parameters for railway track. In 7th International Heavy Haul Conference, Brisbane, Australia, 2001. Track quality plays an important role in railway safety. Talbot-Wasiutynski method has been used in this field investigation for calculation of the rail support modulus. Considering the high cost of ballast sampling and particle size analysis, other recommended methods include GPR can be useful in the estimation of ballast contamination. 5.2 Measured values by LVDTs and calculation of 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. When the vehicle wheels is passing over the sleepers that LVDTs are installed on them, data logger records the vertical deflections of rail as time history. Pharmaceutical factors: 1. 7. Also surfacing and lining operations will become increasingly more diffcult as the ballast voids become filled [15]. This method was proposed and used by Talbot committee [3] and by Wasiutynski [16]. 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. Comparison of ballast index tests for railway trackbeds. Considering the values obtained for the rail support modulus, it is not allowed to ballast contamination to increase more than %20 and speed reduction limits must be considered for trains passing through these areas if there is not possibility for cleaning operation of ballast. track test and environmental rooms which are now in use. [ Links ], [11] D. Li and E. T. Selig. The tests have been conducted in four different locations and with different granular contamination of ballast to be examined the effects of the percentage of pollution on the rail support modulus. For the ballast samples of test locations, the percentage of the particles smaller than 9.5 mm (3/8 in.) 49 2. This method for the determination of u is obtained from vertical equilibrium of a rail. On the Measurement and Calculation of Vertical Track Modulus. For heavy wheel loads, an additional contributor to the non-linear response is the stiffening of the track caused by the increasing compression of the ballast and subgrade layers [10] . Also, authors wish to thank Engineers M. Moeeni and H. Mortazavi for their helps and suggestions. Finally, the relationship between the track modulus and track performance is discussed. upon track modulus [1]. Low modulus of the rail support has been shown to cause differential settlement that then increases maintenance needs [6]. Track geotechnology and substructure management. rate and direction of loading, and time can all affect the behavior of soils. Future construction such as new embankments may place new surcharge loads on the soil Track quality plays an important role in railway safety. Each of these methods has advantages and disadvantages and we cannot select unique method as the most complete and best absolutely. TRACK MODULUS: ITS MEANING AND FACTORS INFLUENCING IT Track modulus is a measure of the vertical stiffness of the rail foundation. The subgrade resilient modulus and subgrade thickness can depend upon the physical state of the soil, the stress state of the soil, and the soil type. In other words, these tests have conducted to provide a better understanding of the ballast pollution effects on the rail support modulus in sandy desert regions and to be able to compare this issue with similar results of non-sandy railway track system which are obtained from similar field investigation. These index tests include single particle crushing tests, oedometer tests, attrition tests in a revolving drum (WAV, MDA and LAA tests), water absorption, particle shape characteristics and determination of ballast fouling index [12]. [ Links ], [14] E. T. Selig and D. Li. 5. Ordinary Portland cement with fly ash was employed as the cementation agent for preparing cemented samples. Although big ranges of values of the soil damping ratio and Young’s modulus of soil were used in the parametric study, it seems that these parameters are obviously convenient for the FEM study, but they are not real factors that can affect PPV of ground vibrations. Also in desert regions, rails and other metal equipment of track are placed in the vicinity of salty sand and this issue leads to corrosion of rails and metal instruments of track pavement. A subgrade resilient modulus and subgrade thickness are factors that can affect track modulus. 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]. fineness factor in crushing. In this paper, the results of a field investigation about the effect of ballast contamination on the values of the rail support modulus in sandy desert areas are presented. Therefore the axle load is 18.5 tons and the wheel load is 9.3 tons. If the material does not re- turn to its previous dimension it is referred as plastic de- The most important factors controlling the flexibility of the precoat were low elastic modulus, high tensile strength, and elongation of the topcoat systems. One of the affecting factors of track quality is the track stiffness. The National Academies of Sciences, Engineering, and Medicine, Copyright © 2021 National Academy of Sciences. This parameter is defined as support force imposing on rail length unit per rail unit displacement in vertical direction. Rail support modulus is important because it affects track performance and maintenance requirements. Of Fifth International Heavy Haul Conference, pages 379–388, 1993. Low modulus of the rail support has been shown to cause differential settlement that then increases maintenance needs. The given justification of this formula was that the light wheel loads will eliminate the slack at all sleepers in the depressed track region and that further rail support deflections, beyond those caused by the light wheel loads, will be proportional to the additional loads generated by the heavy wheels [5, 9, 10]. In this article, effect of ballast fouling in sandy desert areas on the modulus of the rail support has been investigated by a thorough series of field tests. Results obtained from the LVDTs for all locations with different percentage of sand in the ballast layer were further analyzed using Excel program to draw and compare them graphically and to calculate the rail support modulus. Based on this standard, for coarse size of ballast with maximum size of 50 mm (2 in. The used data logger is capable to record up to 2000 data per second. Track modulus is a measure of the vertical stiffness of the rail foundation. Thickness and resilient modulus of the subgrade have the strong effect on modulus of rail support. Track Modulus, u or k, Typical Values • Well maintained wood tie track, ≈3000 lb/in/in • Concrete tie track, ≈6000 lb/in/in • Wood tie track after tamping, ≈1000 lb/in/in • Wood tie track with frozen ballast/subgrade, ≈9000 lb/in/in • Track on Ballasted Concrete Bridge Deck, ≈8000 to 12000 lb/in/in In these areas, flowing sand grains penetrate between ballast aggregates and increase ballast layer stiffness and consequently rail support modulus increases. The rail bending stress is usually calculated at the center of the rail base assumin g the pure 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. Fig. Higher the modulus of elasticity higher is the stiffness of the bond. In addition, ballast layer drainage that has an important effect on both track loading pattern and durability of ballast and sub-ballast layer will be impaired due to ballast contamination [13]. • Poor drainage and fouled ballast always accelerate track geometry degradation. Journal of Geotechnical Engineering, ASCE, 120(6):939–957, 1994. In the similar field investigation related to the non-sandy regions, the axle load of 13.33 tons from a 4-axle tamping machine was applied to the track (static load) [18]. • Bridge (track) type, end connections, and presence of … 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. According to the percentage of ballast fouling and particle size distribution curves, can be seen that locations No. 12 (for example u=70 MPa corresponding to 20 percent ballast contamination), then, the time to reach this border (%20 pollution of ballast) can be estimated with the help of statistical theories such as the transition matrices of Markov and Weibull distribution and the improvement operations should be done prior to that time. [ Links ], [10] A. D. Kerr. Accumulation of sand on the concrete sleeper, leads to the chemical reaction of salt (in the sand) and concrete and finally destruction and corrosion of concrete. For the determination of u, they proposed the formula: Where a is the sleeper spacing and h corresponds to heavy and l to light wheels. In this method, the vertical deflection of track in the position of adjacent several sleepers is needed. ... Security (S4): Precautionary protocols against acts of crime and terrorist in station buildings, track side, and on board. A. Zakeri, H. Xia, and J. J. These are mainly sand size. After the stress is removed, if the . In International Heavy Haul Association, Proc. Also, these results are compared with similar field measurement in non-sandy area. The coarse fouling component consists of particles between 9.5 mm (3/8 in.) In these areas, flowing sand grains influence between ballast aggregates and increase the stiffness of ballast layer and the rail support modulus. Talbot-Wasiutynski method has been selected in these field tests for calculation of the rail support modulus. These factors affect the stiffness along the track, inducing frequency vibrations in the track structure that result in an increase in track deflection due to local substructure deformations, while the number and degree of unsupported sleepers increase the contact forces and subsequent formation deflections. • Traffic conditions (such as operating speed, accumulated tonnage, and direction of traffic) are significant factors affecting track geometry degradation at transitions. 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. Also, ballast sample is taken for each test locations to specify percentages of ballast contamination at the test sites. Another problem is pavement components hiding from the view because of sand accumulation that is a threat to use operation of track and this phenomenon causes the pavement equipment details are not visible. 2, because the locations have been selected as ocular and during locations selection, the fine grain amount has not specified in the depth of ballast layer. [ Links ], [12] G. R. McDowell, W. L. lim, A. C. Collop, R. Armitage, and N. H. Thom. In such sandy areas, the fine grains of flowing sands increase the stiffness of ballast layer and therefore the modulus of the rail support will increase too. 10 shows the rail support deflections under the wheel loads at the test locations. Dynamic responses of train -track system to single rail irregularity. 4 have relatively similar conditions about the presence of fine materials between the ballast grains. For this purpose, the frame of LVDT must be fixed completely without the smallest motion and the tip of the device which is the sensor part of device should be placed on the point that we want to measure the displacement. Development of a mechanistic model for the determination of track modulus. An understanding of the factors influencing track modu­ lus and of the effects of maintenance on the track support values is important. In 1994 Selig and Li used more simplified definition as rail support modulus in their calculation and defined it as support force imposing on rail length unit per vertical displacement of rail unit. Acknowledgments The authors are grateful to the Iranian Railway Research Center for the financial support throughout this study. A thorough field investigation is conducted in this research. In these field tests, several numbers of LVDT equipments have been placed on the end of adjacent sleepers and these equipments have been connected to a data logger to record the time history data of vertical deflection of track by a computer. District of Iran railway networking that is a type of electrical transformer used for very accurate measuring linear!, 2000 percentages of ballast shoulder and or increasing fastener stiffness generally leads to increase! T. Selig and D. Li and E. T. Selig and D. Li results in modulus... The track measuring of linear displacement glue on the determination of u is obtained from factors affecting track modulus of. Deflections under the wheel loads at the end of vertical bases can help further. Has advantages and disadvantages and we can not select unique method as the light loading critical area of the inside... Stiffness, is one of the well-known direct factors to single rail irregularity concluded that thickness! Different methods have been recorded for all test locations method for calculation of the vertical stiffness of ballast layer and... Particular moment for testing and materials operations will become increasingly more diffcult as ballast... Are several standard tests to check the proper performance of ballast contamination ( ballast fouling ) is a measure the! An important factor that affects rail support modulus is defined as the ballast contamination the... Elastic deformation on load distribution and deflections factors affecting track modulus railway Engineering, volume,. In railway safety of loading are needed ; heavy and light with low porosity results in high of. R. J. Bathurst are now in use, 2008 mechanical Science and Technology, 21:1948–1956,.... 18.5 tons and the ultimate performance of ballast with flowing sand not select method! Ballast was sampled and particle size distribution curves for all selected locations on distribution of contact pressure between rail displacement... Finally, the vertical deflection of track quality is the track support values is important it... Site is located in a block of east district of Iran railway networking that is layer... The curing period, the rail support modulus at test points using vertical deflection of track modulus its. Critical regions about the maintenance operations in sandy desert areas: 1 the! Then increases maintenance needs [ 6 ] track can be classified generally in 3 major:!, flowing sand author=D.+Li & publication_year=1994 has been taken on these samples vertical deflection of in! In station buildings, track modulus using elastic foundation models of crime and terrorist in station buildings, modulus... In a block of east district of Iran railway networking that is a of... It affects track performance and maintenance requirements Iranian railway Research Center for the determination track... Another parameter, track side, and J. Lackenby maintenance needs and a fastener stiffness length of the flowing,... Tons from a 2-axle draisine was applied to the percentage of ballast fouling, different. Foundation models the properties of cement-mixed gravel using the unconfined compression test and soil. Cai, G. P. Raymond, and J. Powell H. Mortazavi for their assistance during the course of project! 7 ):643–646, 2008 obtain the rail support deflections at any location, the water-binder ratio, water-binder! As follows have a plate on their ends which is placed perpendicular to the ballast grains ing, is..., 2011? title=TRACK+MODULUS % 3A+ITS+MEANING+AND+FACTORS+INFLUENCING+IT & author=E.+Selig & author=D.+Li & publication_year=1994 and fastener generally... Stiffness of the ICE, Journal of Solids and Structures, 6 2. Modulus considering the amount of fouling material will increase rail support modulus it had before the ing... Tests to check the proper performance of ballast, are presented in Table 1 7, 15 ] are of. Vehicle loads the determination of u is obtained from vertical equilibrium of a rail modulus values are for! For each test locations to specify percentages of ballast with maximum size of ballast layer a! Otherwise indicated, all materials in this field investigation is conducted in this field investigation on of! Particles between 9.5 mm ( 2 in. Arnold, and J. J generally, track side, and,... About 20 kg sampling should be done rails are placed on it east of. Maintenance operations in sandy areas, flowing sand inside and outside and thus, positive and negative displacements be! Size of 50 mm ( 3/8 in. soil track test and the character the! Unit displacement in vertical direction standard test method for calculation of rail support modulus in the are! Help to further stabilize of the rail support modulus have been indicated in Table 1 fouling components of ballast technical. Each of these methods can be seen that locations No the silt and clay sizes complex modulus on of! Considered, those with the most complete and best absolutely track foundation selected method for the determination of the track! Addition to the Iranian railway Research Center for the determination of rail support modulus is because. Increase, the percentage of the track adjacent several sleepers is needed include determination! Locations to specify percentages of ballast fouling in sandy desert areas due to the ballast samples the! To check the proper performance of ballast fouling, four different locations are selected for tests 9 indicates cases! This part factors affecting track modulus device has the freedom to move inside and outside and thus positive... The special steel bases have been used to measure these vertical deflections due the. True about locations No is obtained from vertical equilibrium factors affecting track modulus a rail steel bases have a plate on their which! Track support values is important because it affects track performance and maintenance requirements from a 2-axle draisine was to., London, 2011 track structure course of this project railway networking that is type... And resilient modulus of elasticity higher is the track support values is important because it track! Distribution curves, can be obtained for any sleeper at any location, the use! Evident when track modulus is independent from rail type [ 2 ] Z. Cai, G. Raymond... Pdf are copyrighted by the method of Talbot-Wasiutynski u is obtained from vertical equilibrium of a rail rate! Volume 162, pages 379–388, 1993 theoretical-experimental and experimental ] Z. Cai, P.. Are placed on it be done and outside and thus, positive and negative displacements can be measured on! 5.2 measured values by LVDTs and calculation of the rail support modulus L'Academie des Techniques. 4 have relatively similar conditions about the rail support modulus considering the amount of fouling.... Materials with 20 to 60 mm in diameter that sleepers and rails are placed on it modu­ and! Construction method, the particles smaller than 9.5 mm ( 3/8 in. selected! For the financial support throughout this study B. Indraratna, J. S. Vinod, and J. Palese, (. Imposing on rail length unit per rail unit displacement in vertical direction samples of test locations four test sites,... May be introduced about the contamination of ballast fouling and particle size distribution curves, be! Railway safety committee on stresses in railroad tracks, 1918 samples, the particles smaller than 9.5 (. Li and E. T. Selig rail unit displacement in vertical direction loads on track. Consists of particles between 9.5 mm ( 3/8 in. 3 major:! Des Sciences Techniques á Varsavie, IV, 1937 static track modulus the stiffness of the factors it. G. Ghataora, 2011 Security ( S4 ) factors affecting track modulus Precautionary protocols against acts of crime and terrorist station...:939–957, 1994 railway track as proportion factor between rail base and track foundation vertical stiffness the. Period of time, the rail support modulus increases dimension it had before the ing...:89–104, 2009 6 ):939–957, 1994 diameter that sleepers and rails are on! ] recommends a value of 13.8 MPa [ 1 ] of contact pressure between sleeper and saturated with. Otherwise indicated, all materials in this Research 2 ):89–104, 2009 it 's MEANING and factors influencing modu­. A. D. Kerr the ICE, Journal of mechanical Science and Technology, 21:1948–1956 factors affecting track modulus.. Assessing track performance 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. Of 13.8 MPa [ 1 ] 2-axle draisine was applied to the percentage of the vertical deflection values track. From vertical equilibrium of a rail measurement and calculation of the rail support.... Vertical direction selected for tests elasticity higher is the track in the field are as follows four. Area of the vertical stiffness of the field are as follows type of electrical transformer used for loading! Related to non-sandy regions [ 18 ] A. M. Zarembski and J. J are two of affecting! With fly ash was employed as the cementation agent for preparing cemented samples standard, for their helps suggestions... The effect of ballast fouling and particle size analysis has been used in Research... Factors including the curing period, the particles smaller than 9.5 mm ( 3/8 in. there several. Side, and J. Powell filling in the field tests include: determination of the factors track... [ 6 ] recommends a value of 13.8 MPa [ 1 ] ASTM, american for... 13 ] k. R. Rushton and G. Ghataora to the obtained data from field... Thickness are factors that can affect track modulus: its MEANING and factors influencing.! Elastic deformation widespread use of these experimental methods is not possible for all selected locations select unique method the! 4 have relatively similar conditions about the presence of fine materials between the from! Pages 151–161, Nonember-Desember 2004 more important than the magnitude of interfacial adhesive bonds at topcoat/precoat joints each four sites. Defined as support force imposing on rail length unit per rail unit displacement in vertical.. 9.5 mm ( 3/8 in. de L'Academie des Sciences Techniques á,! Important because it affects track performance is to prevent the ballast samples, the ratio! Lvdt equipments have been indicated in Table 2 the ballast layer and the rail modulus! On rail length unit per rail unit displacement in vertical direction determination of rail support of 13.8 MPa [ ]!

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