MINISTRY OF SCIENCE AND TECHNOLOGY DEPARTMENT OF TECHNICAL AND VOCATIONAL EDUCATION DEPARTMENT OF CIVIL ENGINEERING
CE4017-RAILWAY ENGINEERING (SAMPLE QUESTINS AND SOLUTIONS)
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SAMPLE QUESTIONS CHAPTER 1 HISTORY AND DEVELOPMENT
1. Discuss the advantages of railways. 2. Give a classification of transportation. Discuss in brief. 3. Enumerate the advantages and disadvantages of railway transport over other modes of transport facilities. CHAPTER 2 TRACKALIGNMENT
4. (a) Write a small note on the need of construction of a new railway line. (b) List the factors influencing the selection of a good railway track alignment. 5. Discuss the requirements of a good rail alignment. CHAPTER 3 RAILWAY SURVEYS
6. Explain the reconnaissance survey for a new railway lines. 7. Explain the preliminary survey for a new railway lines. 8. Explain the location survey for a new railway lines. CHAPTER 4 RAILS
9. (a) Define the rail and describe the functions of rail. (b) What are the causes for the wear of rails? 10. Describe the main requirements of an ideal rail section. 11. Compare the flat-footed rail and bull headed rails. 12. (a) Write the advantages and disadvantages of flat-footed rails. (b) Write the advantages of welding of rails. 13. Describe the corrugated rail and the possible factors, which contribute to the commencement and development of the corrugations. CHAPTER 5 SLEEPERS
14. What are the function of sleepers and requirements of a good sleeper? 15. (a) List the types of sleeper. (b) Describe the advantages and disadvantages of timber sleepers. 16. (a) Define the sleeper. (b) Describe the advantages and disadvantages of concrete sleepers. 17. Describe the advantages and disadvantages of the steel sleepers.
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SAMPLE QUESTIONS CHAPTER 1 HISTORY AND DEVELOPMENT
1. Discuss the advantages of railways. 2. Give a classification of transportation. Discuss in brief. 3. Enumerate the advantages and disadvantages of railway transport over other modes of transport facilities. CHAPTER 2 TRACKALIGNMENT
4. (a) Write a small note on the need of construction of a new railway line. (b) List the factors influencing the selection of a good railway track alignment. 5. Discuss the requirements of a good rail alignment. CHAPTER 3 RAILWAY SURVEYS
6. Explain the reconnaissance survey for a new railway lines. 7. Explain the preliminary survey for a new railway lines. 8. Explain the location survey for a new railway lines. CHAPTER 4 RAILS
9. (a) Define the rail and describe the functions of rail. (b) What are the causes for the wear of rails? 10. Describe the main requirements of an ideal rail section. 11. Compare the flat-footed rail and bull headed rails. 12. (a) Write the advantages and disadvantages of flat-footed rails. (b) Write the advantages of welding of rails. 13. Describe the corrugated rail and the possible factors, which contribute to the commencement and development of the corrugations. CHAPTER 5 SLEEPERS
14. What are the function of sleepers and requirements of a good sleeper? 15. (a) List the types of sleeper. (b) Describe the advantages and disadvantages of timber sleepers. 16. (a) Define the sleeper. (b) Describe the advantages and disadvantages of concrete sleepers. 17. Describe the advantages and disadvantages of the steel sleepers.
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CHAPTER 6 BALLAST
18. (a) List the requirements of good ballast. (b) Describe the functions of ballast. 19. What is ballast? Why is ballast used for in the railway track? Write briefly on the different types of ballast used. CHAPTER 7 RAIL FIXTURES AND FASTENINGS
20. (a) List the various types of fixtures and fastenings in a permanent way. (b) Describe the functions of fish plates in a rail joint 21. Explain briefly the following. (a) Spikes and Chairs (b) Keys, Cotters and Tie Bars (c) Bearing Plate (d) Check Rails and Guard Rails (e) M.C.I Inserts and Rubber Pads CHAPTER 8 GEOMETRIC DESIGN OF TRACK
22. (a) What do you understand by the following terms for the section of the track? i.Grade compensation on curves ii.Widening of gauge (b) List the various types of gradients that are adopted in laying a railway track. 23. What are the elements of a simple circular curve? 24. (a) A five degree curve diverges from a main curve of 4º in an opposite direction in the layout of a B.G. yard. If the speed on the main curve is restricted to 54.53 kmph, determine the speed restriction on the branch line. Assume permissible cant deficiency as7.5 cm. (b) What do you understand by cant deficiency? If an 8º curve track diverges from main curve of 5’ in an opposite direction in the layout of a B.G. yard, calculate the super elevation and the speed on branch line, if the maximum speed permitted on the main line is 45 kmph. 25. (a) Explain why super elevation is necessary on a curve alignment. (b) Explain briefly types of classification of horizontal curves.
CHAPTER 9 POINTS AND CROSSINGS
26. Write short notes in the followings: (i) Left hand and right hand turn outs (ii) Theoretical nose of crossing and Actual nose of crossing (iii) Splice rails and Wing rails (iv) Point rails and Stock rails (v) Tongue rails and Stretcher bar
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27. (a) On a straight B.G. track, a turnout takes off as an angle of 6º 42’ 35” Angle of switch = 1º 34’ 27” Length of switch rail = 4.37 m Heel divergence = 11.43 cm Length of straight arm = 0.85 m. Determine the radius and the crossing lead. (b) A 1 in 12 turn out is to be provided on a B>G> straight track, calculate (i) radius of the curve lead rail (ii) lead distance, and (iii) over all length of the turn out. Data given: Heel divergence = 133 mm Actual length of switch rail = 6001 mm Theoretical length of switch rail = 6743 mm Distance between toe of crossing and theoretical nose of crossing = 2415 mm Distance between toe of crossing and theoretical nose of crossing = 1498 mm Distance between theoretical nose of crossing and heel of crossing = 3810 mm CHAPTER 10 TRACK MAINTENANCE
28. Describe the followings: (vi) Necessity of track maintenance (vii) Essentials of good track maintenance (viii) Advantages of proper track maintenance 29. Calculate the necessary data for setting out a semi permanent diversion 20 m away from the B.G. track. Assume: radius of the curves = 440 m Gradient along diversion = 1 in 100 Straight proportion of diversion = 50 m Straight length between reverse curve = 30.5 m. 30. Design the layout of a 2 m high BG semi permanent diversion for rebuilding a 4 x 6.1 m bridge on 4 m high line track. Adopt economical specifications.
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SOLUTIONS CHAPTER 1 HISTORY AND DEVELOPMENT 1. Discuss the advantages of railways. Solution Advantages of Railways 1. Political Advantages 2. Social Advantages 3. Economical Advantages
1. Political Advantages The political advantages of railways are as under: a) Railways help to unite the people of different religions, castes, customs and traditions. b) Railways network has enabled the central administration to become more easy and effective. c) Railways have helped in the migration of the population from one region to the other for employment opportunities. d) Railways have contributed a lot for developing national integration. e) Railways have helped during wars for transportation of war equipments and armies. 2. Social Advantages The social advantages of railway are as under: a) Railways provide a convenient, safe and cheap mode of transport for the country. b) Railways have broadened the social out-look of the people. c) Railways have eradicated the untouchability as passengers of different castes travel in the same compartment. 3. Economical Advantages The economical advantages of railway are as under: a) Rails help in transporting the labor from places of unemployment to industrial centers. b) The finish products and the goods can be speedily transported by the railways t the places of their consumption. c) Industries have been developed even far from the places of the raw materials. d) During famines, the railways play a vital role of transporting the food grains and cloths to the affected area. e) Rails have provided employment to millions of people and thus, rails have helped in solving the unemployment problem. f) The land cost increases due to opening of railway lines. g) Rails have helped in fair distribution of population.
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2. Give a classification of transportation. Discuss in brief. Solution 4 major type of transportation system, 1) Land Transport 2) Water Transport 3) Air Transport 4) Continuous flow system
Land Transport (1) Highways (2) Rail Transport Highways A rubber-tired wheel on a smooth, firm roadway features the technology used by auto, trucks, busses, bicycles, motorcycles, taxis, etc.
Railways Flanged-wheel- on rail (steel wheeled of rubber wheeled). Railroads rail transit (MRT, MTR, METRO, etc.)
Water Transport (1) Inland (2) Costal (3) Ocean Nature of artificial channels and bodies of water serve as roadways. Ships, barges, pleasure craft, submarines, etc.
Air Transport (1) Domestic (2) International Use of air space at a more than nominal height above the ground Jest, helicopter, etc.
Continuous Flow Systems Oil Gas Other Pipelines Provides transportation for water, sewage, petroleum, gas, steam, heat, etc. Belts, cable. Conveyors-people movers, escalators, etc.
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3. Enumerate the advantages and disadvantages of railway transport over other modes of transport facilities. Solution Sr. No. 1.
Item Tractive resistance
Highway Transport Pneumatic tires on road experience tractive resistance five times as compared to that of the railways. It is open to all types of vehicular vehicles including pedestrians.
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Right of way
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Cost analysis
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Gradients curves
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Flexibility of Being more flexible it may even movement serve door to door.
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Population
It pollutes the environment more.
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Organization
Highway transport of controlled mostly by private sectors.
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Suitability
It is suitable for lighter goods and for passengers traveling over short distances.
Cost of construction and its maintenance is less. Steeper gradients up to 1 in 30 and relatively sharper curves may be provided.
Rail Transport Tractive resistance is less and hence hauling capacity is more. The track being defined by two rails is suitable to trains designed for the track. Cost of construction and its maintenance is more. Flatter gradients> 1 in 100 and curves up to 10’ on broad gauge tracks, are generally provided. Being less flexible, the movement of trains is restricted between fixed stations. It pollutes the environments less. It pollutes the environment less. Railways are controlled and managed by the Govt. organization. It is suitable for the carriage of heavy goods and for passengers traveling over long distances.
CHAPTER 2 TRACKALIGNMENT 4. (a) Write a small note on the need of construction of a new railway line. (b) List the factors influencing the selection of a good railway track alignment. Solution 4. (a) Need of Construction of a New Track Construction of new railway tracks is required to meet one of the following demands. (1) Strategic reasons: Sometimes it is found necessary to extend the existing railway track to appoint of strategic importance so that in case of an emergency, army and ware equipments can be quickly transported from any to the other point. (2) Connecting trade centers: Sometimes, construction of a new railway track may be found necessary to connect trade centers for quick transportation of goods from the point of production to the point of consumption.
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(3) Political demand: Sometimes, the government may be compelled to construct a new railway line to meet the political demand of the area. (4) Developing a backward area: Sometimes, for the development of a backward area, a new railway line may be provided, Quick transport system develops the area rapidly. (5) Shortening the existing route : Sometimes two stations, a new railway lie might be proposed for quicker movement of the goods and passengers.
4. (b) For selection of a good alignment , the following factors are generally considered: (1) Obligatory points (2) Type of traffic (3) Gauge of the track (4) Geometric standards (5) Topography of the country (6) Economic considerations (7) Other considerations 5. Discuss the requirements of a good rail alignment. Solution Requirements of a Good Alignment While selecting an alignment of a new railway line, convenience and comfort of the passengers must be kept in mind. An ideal alignment should fulfill the following requirements: (1) Purpose of the track: The alignment of the track should meet the basis purposes of the route. The railway lines are generally laid to meet the following purposes. a Transportation services: Railways are usually constructed to facilitate the transportation of the goods and passengers of the area. b Political and strategic considerations: The railway track may be required to meet the political demand and to link stations of strategic importance for defence purposes so that in case of a war, army may move from one place to the other quickly. c To connect industrial towns: Some times a railway track may be provided to link for consumption. In other words railways boost up the trade. d To open up new track: A railway track may be required to tap the resources of remote places, which are rich in natural minerals, etc. e Shortening the existing track: A badly aligned railway track having zig-zag route might be required to be replaced by a track alignment having a shorter distance. (2) Feasibility: The proposed alignment of eh railway track should fit in the general planning of the country. (3) Economy: An alignment is said to be economical if its cost of construction and maintenance is least. To obtain an economical alignment, the following considerations are kept in mind: a. Distance: An economical alignment is the shortest route between the given stations. In practice, it is neither possible nor feasible to have a straight alignment. The track is generally required to be deviated to avoid unfavorable areas such as marshy land or mountainous terrain. b. Cost of construction: To obtain an economical alignment, the construction cost should be minimum. This can be achieved by avoiding the areas involving excessive cuttings and fillings, construction of long bridges, viaducts, tunnels, etc. these factors are minimized by alignment the track along or near the water shed line.
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c. Maintenance cost: As the maintenance cost of the track is a recurring expenditure, it should be minimum, long bridges, viaducts and tunnels. The steep gradients that increase the wear on rails should also be avoided. d. Operation cost: To obtain and economical alignment, it should be ensured that the operation cost is minimum. This may be achieved by adopting a shortest direct route and also by a avoiding steep gradients enroute. (4) Safety: The proposed alignment should ensure safety for the operation staff, traveling passengers and goods. To achieve safety, horizontal and vertical curves should be properly designed. The slopes of eh cuttings and fillings should be made stable and the foundations of the embankments should be properly maintained t avoid their failure. (5) Aesthetic aspects: The alignment should be laid across pleasing natural surroundings so that traveling passengers enjoy the journey.
CHAPTER 3 RAILWAY SURVEYS 6. Explain the reconnaissance survey for a new railway lines. Solution Reconnaissance Survey A reconnaissance survey should provide the following information: 1) Accurate topography of the country. 2) Towns, railways, river crossings, tunnel sites, etc. 3) Geological characteristics of the soil of the area affecting foundations for bridges and stability of the project line. 4) Width of waterway required for rivers and drainages. 5) Maximum flood levels of the intercepting natural drainages. 6) Availability of building materials and labor. 7) Probable radii of the horizontal curves. 8) The total length of the route. 9) Amount of expected earth work. 10) The approximate cost of construction of each probable line. Factors to be kept in view during reconnaissance survey: The following factors should be kept in view during reconnaissance survey: 1. Area: The reconnaissance survey should be carried out for the entire area and not along the line. 2. Existing roads: Alignment of the existing roads should not be mistaken as suitable route for the new rail track. Road alignments are seldom useful for the construction of a railway line. 3. Starting of route: The engineer should not reject a particular route only because its start is bad, i.e. a sudden rise of fall. He must ascertain whether the route is bad for a long distance thereafter. 4. Assumption: The engineer should never declare his decision by simply assuming the nature of the ground. He should personally verify the details in the field. 5. Survey route: Each route should be surveyed independently from either end. 6. Occular illusion: The following ocular illusions should be prevented: a) Estimating wrong length b) Estimating wrong curvature
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c) Overlaps of hills which may observe a lake of river due to mirage. In fact no such lake exists there. d) In flat countries, the observer may observe a lake of river due to mirage. In fact no such lake exists there. 7. Revenue: the probable revenue from a new railway line from 15 km on either side. 7. Explain the preliminary survey for a new railway lines. Solution Preliminary Survey For preliminary survey for large railway projects, the field work under control of location engineer may be divided among the following parties: 1. Transit party. 2. Leveling party 3. Topographic party. Fieldwork of the transit party: The following steps are involved: 1. Clearing the route from vegetative growth. 2. Fixing a peg on the starting point and establishing three points in its vicinity. 3. Selecting a forward station on the straight line. 4. Determining the true bearing of the first traverse side by making astronomical observations to either sun or star. 5. Measuring the horizontal distance of the first traverse leg with a 30 m steel tape. 6. Setting up the transit at the second station and fixing the stakes on the third station as well as on the first station. 7. Observing the direct or the back angle between the adjacent traverse legs. 8. Clearing the proposed alignment of the route and fixing stakes at the proposed traverse stations. 9. Observing the direct angles at succeeding stations accurately. 10. Checking the azimuth of the first and the last lines by making astronomical observations. If the traverse is long, intermediate checks after about 15 km, need be provided for the azimuth. 11. Connecting the traverse to triangulation stations and intersected points enroute where possible. 12. Observing prominent points such as church spires, temples, mosques, pylons, etc. on either side of the route at least from three consecutive traverse stations, to chack the accuracy of the instrument work. 13. Fixing stakes at 30 m intervals and also at the ends of traverse line. 14. Measuring the distance between stakes with a 30 m steel tap. Chainage is carried forward continuously from the beginning of the survey, i.e. zero station. Every 30 m station is named as full station and the intermediate stations as plus stations. 15. Fixing stakes at intersecting with roads, railways, canals, streams, etc. and also recording their chainages. 16. Plotting each day’s work daily to detect gross mistakes and omissions. Level Party: The level party following immediately the transit party to run longitudinal section of the traverse line. Following steps are involved: (1) Determine the elevations of the ground at all stakes, intersections with roads, railways cart tracks, on the points of changes on slope in the usual way. (2) Determine the bed levels, depth of water and highest flood level of intersecting streams
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(3) Established bench marks on objects which are likely to be permanent such as rocks, wells, tree toots, etc, at about 500 meter intervals and give their full descriptions to be referred to for subsequent work. (4) Read the staff to the nearest 0.01 m at full stations and points of he change on slope and up to 0.005 m at transit points, transit stations and benchmarks. (5) Check the leveling work by connecting the level lines to the existing permanent benchmarks or G.T.S. benchmarks enroute. (6) Plot the profile of the ground daily along the traverse line on the following scale: Project Horizontal Scale Vertical Scale Railways 1:2000 1:200 Topographic Party: The topographic party prepares the topographic map of the narrow belt along the route. The following steps are involved: (1) Plotting the natural and artificial details, rivers, streams, roads, railways, canals, villages, property lines, etc. (2) Plotting the contours at suitable vertical interval. (3) Collecting of the information regarding the character of land, cultivation, excavation, rocky feature, ect. 8. Explain the location survey for a new railway lines. Solution Location Survey Location survey is carried out in the following two stages: 1. Office location survey 2. Field location survey Office location survey: the following steps are involved: (1) Draw the straights along the most suitable alignment of the route in pencil. (2) Draw the curves by means of a curve template of known degrees of curvature. (3) Prepare a profile along the new line with the help of contours on the map and make the grade line on the profile in pencil. While choosing the probable location of the route, the following factors are considered: (i) Minimum gradient. (ii) Minimum curvature (iii) Equalization of the earthwork. (iv) Heavy earthwork. (v) Minimum number of expensive bridges. (vi) Minimum number of retaining and breast walls.
Field Location Survey: It is carried out to set out on the ground the alignment of the route, finally decided on the preliminary plan. Minor changes are permissible to be made in the field at this stage if found necessary. The central line of the projected line is set out on the ground as follows. (1) From the preliminary map, scale off the positions of the various points to be transferred on the ground. To do this, perpendicular offsets may be made form the traverse line. The chainages of the intersections of the line with main traverse may be ascertained and if necessary, the angles and distances may also be used. (2) Prolong the adjoining tangents and find their point of intersection. Measure the angle of intersection carefully.
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(3) Knowing the radius of the curves and the angle of intersection of tangents, compute the necessary data for setting out the simple curve. (4) Drives stakes at every 30 m intervals and hubs at all intermediate theodolite stations intersection points of the tangents and the point of tangencies of eh curves. Give their proper reference in the field book. (5) Draw sketches with proper dimensions for important features such as roads, railways, streams, etc,. on the right hand side of the field book. (6) Carrying out the leveling over the located line. Prepare a profile and establish a suitable the profile. (7) Plot the finally located line known as filed location on the preliminary map and complete the profile. (8) Show vertical curves on the final profile. (9) Calculate the approximate quantities of eh earthwork by drawing cross-sections of the located line on the preliminary contour map. (10) Depict all importance features in the close proximity of the line i.e all the point where hubs are set, all the benchmarks and the boundaries of private properties on the preliminary map. (11) Collect the names of the owners of private properties to facilitate the acquisition of the land for the permanent way. CHAPTER 4 RAILS 9. (a) Define the rail and describe the functions of rail. (b) What are the causes for the wear of rails? Solution (a) Rail The high carbon rolled steel sections which are laid end to two parallel lines over sleepers to provide a continuous and level surface for the trains to move and for carrying axle loads of he rolling stock, are called rails. Functions of the Rails The main functions of rails in a railway track are as under: (1) Rails provide a continuous and level surface for the movement of the trains with minimum friction with steel wheels of the rolling stock. (2) Rails provide strength, durability and lateral guidance to the track. (3) Rails transmit the axle load to sleepers, which transfer the same load to the underlying ballast and formation. (4) Rails bear the stresses developed due to heavy vertical loads, breaking forces and temperature variance. (b) Causes for the wear of the rail The main causes of rail wear are as under: (1) The impact of moving loads. (2) The force exerted by the locomotive during acceleration. (3) The force exerted by the locomotive while retardation. (4) The force exerted by the wheel brakes. (5) The abrasion due to rail wheel interaction. (6) Climatic conditions, i.e. temperatures, rain, sand, etc.
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10. Describe the main requirements of an ideal rail section. Solution
An Ideal Rail Section The main requirements of an ideal rail section are as under: (1) The section of the rail should be such that the load of eh wheels is transferred to the sleepers without exceeding the permissible stresses. (2) The section of the rail should be able to withstand the lateral forces caused due to fast moving trains. (3) The underside of the head and top of the foot of the rail section should be of such aslope that the fishplates fit snugly. (4) The center of gravity of the rail section should preferably coincide the center of the height of the rail so that maximum tensile and compressive stresses are nearly equal. (5) The web of the rail section should be such that it can safely bear the vertical load without buckling. (6) The head of the rail should be sufficiently thick for adequate margin of vertical wear. (7) The foot of rail should provide sufficient bearing area on the underlying sleepers so that the compressive stresses on the timber sleeper remain within permissible limits. (8) The section of the rails should be such that the ends of two adjacent rails can be efficiently jointed with a pair of fish plates. (9) The surfaces for rail table and gauge face should be sufficiently hard to resist the wear. (10) The contact area between the rail and wheel flange should be as large as possible to reduce the contact stresses. (11) The specimen of rail should be able to withstand the blow of a falling weight in the test specified by the specifications. (12) The composition of the steel should conform to the specifications adopted for its manufacture by Open Hearth of Duplex Process. (13) The overall height of the rail should be adequate to provide sufficient stiffness and strength as a simply supported beam. (14) The stiffness of a rail section depends upon the moment of inertia. The economical design should provide maximum moment of inertia per unit weigh of rail with due regard to other factors. (15) The section modulii of the rail section and that of a pair of fish plates should be adequate so as to keep the rail and fish plates within permissible limits. (16) The foot of the rail should be wide enough so that the rail is stable against overturning.
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11. Compare the flat-footed rail and bull headed rails. Solution Comparison of flat-footed and bull headed rails Flat-footed rails These are more strong for the same crosssectional area and weight. Bearing plates for fixing these rails on wooden sleepers are required. Fastening of rails to sleepers is less costly on wooden sleepers. Arrangement and maintenance of points and crossing is simple and cheaper. The rolling wheels affect the rail fittings and thus disturb the alignment.
Daily inspection of the track with these rails, is not required. Initial cost of these rails is low. Replacement procedure for these rails is easy. These rails provide more rigidity t the vertical load. The maintenance cost is less. These are more suitable due to stability economy and strength.
Bull headed rails These are less strong for the same cross sectional area and weight. Bearing plates for fixing these rails on wooden sleepers are not required. Fastening of rails to sleepers is more costly on wooden sleepers. Arrangement and maintenance of points and crossing is complicated and costlier. The rolling wheels do not affect the rail fittings quickly. These maintain good alignment. Daily inspection of these rails for the wooden keys, is required. Initial cost of these rails is high. Replacement procedure for these rails is complicated. These rails provide less rigidity t the vertical load. The maintenance cost is more. These are more suitable where lateral loads are more important than vertical load.
12. (a) Write the advantages and disadvantage of flat-footed rails. (b) Write the advantages of welding of rails. Solution (a) Advantages of the Flat-footed Rails It provides better rigidity and stiffness to the track to resist both lateral and vertical forces. (1) It is very simple to fix these rails to the sleeper, with the help of spikes. Neither chairs nor keys are required in the case of flat-footed rails. (2) Maintenance of the points and crossings of flat-footed rails is very simple. (3) The cost of construction of flat-footed rails is lesser than that of the other types of rails. (4) These rails are less liable to develop kinks and thus provide a more regular top surface than the other types of rails. (5) These rails distribute the train load over a large area on the sleepers. Flat-footed rails provide greater track stability and also provide longer life to the sleepers. (6) The rail failures are few and thus the maintenance cost is low. Disadvantages However, in case of flat-footed rails, the impact of rolling wheels directly affects the rail fittings. This is why the fittings of flat-footed rails get loosened more frequently than in the case of bull-headed (B.H) rails.
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(b) Advantages of Welding of Rails
The main advantages of welding of rails are as under: (1) Welding of rails increases the life of the rails due to decrease in wear of the ends. (2) Welded rails provide more comfort to the passengers due to smooth running of wheels over welded joints. (3) Welding of rails reduces the creep because frictional resistances increase with the increase in rail length. (4) As discontinuity of rails is reduced, the defects such as hammering rail joints, displacement of joint, disturbance in alignment and running surface, are also eliminated. (5) A welded rail panel provides better track circuiting on the electrified tracks. (6) Welded rails provide better performance and reduce the effects of impact on large span bridges. (7) Long welded rail length dampens the intensity of high frequency vibrations due to moving loads. (8) Welding increases the life and decreases the wear of rails. (9) By welding of rails, the cost of track construction decreases due to elimination of a large number of rail joints. (10) Fast and heavy traffic may be permitted on track with welded rails. (11) The use of long welded rails, affords better longitudinal, lateral and vertical stability to the track. (12) In a welded rail panel, the number of joints is less. This saves the fuel consumption as it eliminates the loss of strain and impact energy at the rail joints. (13) In welded rail panels, the risk of sabotage and accidents, are considerably reduced. (14) Welding of rails reduces the maintenance cost by about 20% to 40%. 13. Describe the corrugated rail and the possible factors, which contribute to the commencement and development of the corrugations. Corrugated rail The rails whose top surface develops alternate ridges and hollows varying in shape and size (0.05 mm to 0.4 mm in depth), 2 to 8 cm apart, are called corrugated rails, when vehicles pass over such corrugations, an unpleasant noise is created, probably due to the locking of air in the corrugations. Such rails are also called roaring rails. The possible factors, which contribute to the commencement and development of the corrugation, are: (1) High speed of running trains. (2) Rigidity of railway track. (3) Excessive tight or loose gauge. (4) Non-uniformity of the diameter of locomotive wheels. (5) Coning of wheels. (6) Steep gradients. (7) Slippage of locomotive wheels. (8) Small spacing between driving axles of the locomotives. (9) Soft and loose formation.
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(10) (11) (12) (13) (14) (15) (16) (17)
Presence of high humidity and dust in the atmosphere. Use of light wagons and coaches. Sudden application of brakes. Using a steel of high nitrogen content and high tensile strength. Vibrations of the rails. Excessive phosphorus content in the steel composition. Long tunnels. Electrified rail track
CHAPTER 5 SLEEPERS 14. What are the function of sleepers and requirements of a good sleeper? Solution Functions of Sleepers In a railway track, sleepers perform the following functions: (1) To hold the rails t proper gauge in all situations. i.e. exact gauge along straights and flat curves, slightly loose on sharp curves and slightly tight in diamond crossings. (2) To support the rails firmly and evenly throughout. (3) To distribute the load transmitted through rails over large area of ballast underneath or to the bridge girders as the case may be. (4) To hold the rails to proper level in turnouts and crossovers, and at 1 in 20 in ward slope along straight tracks. (5) To provide and elastic medium between the rails and ballast and also to absorb the vibrations caused due to moving axle loads. (6) To maintain proper alignment of the track. On curves proper cant is provided by raising the outer rail and tamping he required quantity of ballast bellow th rails. (7) To provide the general stability of the permanent way throughout. (8) To provide the insulation of track for the electrified for signaling. (9) To provide easy replacement of the rail fastenings without any serious traffic disturbances. Requirements of a good Sleeper A good sleeper should meet the following requirements: (1) The initial cost and the maintenance cost of the sleepers should be low. (2) The fittings required for fixing the rails on to the sleepers, should be simple which can be easily adjusted during the maintenance. (3) The crushing strength fo the sleepers should be more with moderate weight. (4) They should be able to maintain a perfect alignment, gauge and levels of the rails and should afford efficient adjustment and maintenance. (5) They should provide sufficient bearing area to hold the rail seats and for the ballast to be supported on, to resist the crushing due to movement of heavy axle loads. (6) The sleeper spacing should be such as t remove and replace the ballast during regular maintenance operation. (7) They should be capable to resist the shocks and vibrations caused due to fast moving vehicles at high speeds.
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(8) They should provide insulation facilities for track circuiting in the electrified sections. (9) The sleepers should be strong enough to withstand the pressuer during packing process. (10) The sleepers should be of such a design that they remain in their positions and do not get disturbed due t moving trains. (11) The material used for the sleeper be such that it does not attract the sabotage and the theft qualities. 15. (a) List the types of sleeper. (b) Describe the advantages and disadvantages of timber sleepers. Solution (a) Types of Sleepers 1. Timber sleepers 2. Steel sleepers 3. Cast iron sleepers 4. R.C.C sleepers 5. Pre-stressed concrete sleepers. (b) Advantages and disadvantage of wooden Sleepers Advantages of wooden Sleepers The wooden or timber sleepers possess the following main advantages: (1) They have proved very useful for heavy loads and high-speed trains. (2) They are cheap and easy to manufacture. (3) They can be handled easily without any damage. (4) They maintain the correct alignment. (5) They are most suitable for track circuiting. (6) They can be used with or without ballast. (7) They can be used for gauntlet tracks. (8) They are suitable in the areas having yielding formations. Disadvantages of Wooden Sleepers They are easily subjected to wear and decay due to various factors, i.e. vermin, white ants, rail-cutting, warping, etc. Hence, these have a short life. (1) They do not maintain the gauge accurately. (2) They easily develop cracks with beater packing. (3) They require the highest maintenance cost as compared to other types of sleepers. (4) They get easily disturbed from their positions under heavy loads. (5) They need special treatment for fire protection. (6) Their scrap value is low. (7) They are not suitable for modern LWR track because of their lighter weight.
16. (a) Define the sleeper. (b) Describe the advantages and disadvantages of concrete sleepers. Solution (a) Sleeper Wooden, cast iron or R.C.C members which are laid transverse to the track alignment to support the rails and to transfer the load from the rails to the underlying ballast are called wooded sleepers, cast iron sleepers or R.C.C. sleepers respectively. (b) Advantages and Disadvantages of Concrete Sleepers
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Advantages (1) The concrete sleepers are quite heavy and thus provide longitudinal, lateral and vertical stability. Because of their weight, these sleepers are more suitable to LWR tracks. (2) The concrete sleepers result in reduced rail bending stresses. (3) The concrete sleepers reduce the wear of rolling stocks. (4) The concrete sleepers produce less vertical motion and thus provide a comfortable journey due to less noise. (5) The concrete sleepers have flat bottoms. That’s why mean modern method of track maintenance i.e. MSP and machine maintenance can be suitably employed. (6) The concrete sleepers are neither in flammable nor subjected to damage by corrosion or termite. (7) These sleepers have a long useful life of 50 years. It means rail and sleeper renewals can be matched. (8) The concrete sleepers with their fastening system maintain gauge, cross levels, twist, alignment, longitudinal level and unevenness of the track. (9) The concrete sleepers are suitable for track circuiting. (10) The concrete sleepers can be manufactured from local resources. Disadvantages (1) They are not economical because of high cost of construction. (2) In case of derailments, heavy damage is caused. (3) High standard of maintenance of track is required. (4) The design and construction are both complicated. (5) They are more rigid. (6) They do not have any scrap value. 17. Describe the advantages and disadvantages of steel sleepers. Solution Advantages of steel Sleepers The steel sleepers possess the following advantages: (1) They are manufactured by a simple operation. (2) They can be easily handled as theses are light in weight as compared to other types of sleepers. Hence, damages during handling and transporting are less. (3) Less number of fastenings are required and that too simple in nature. (4) The maintenance and adjustment of gauge are easy as compared to the other of sleepers. (5) These sleepers are rolled sections in one piece. (6) Their life is longer than that of other types of sleepers. (7) They provide better lateral rigidity to the track. (8) They are not attacked by vermins. (9) They are not susceptible to fire hazards. (10) Their scrap value is good. Disadvantages of Steel of Sleepers The steel sleepers possess the following disadvantages: (1) They get easily rusted and corroded. (2) They develop cracks at rail seats or near lugs. (3) Their lugs get broken easily. (4) The steel sleepers do not provide effective track circuiting.
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(5) The steel sleepers can only be for the type of rails for which theses are manufactured. (6) These develop the tendency to become center bound because of slope at both ends. (7) The overall cost of steel sleepers is more than that of timber sleepers. CHAPTER 6 BALLAST 18. (a) List the requirements of good ballast. (b) Describe the functions of ballast. Solution (a) Requirements of Good Ballast Ideal ballast should possess the following characteristics: (1) It should resist crushing under dynamic loads. (2) The designed depth of the ballast should be able to distribute the weight of passing trains on the formation underneath uniformly. (3) It should not make the track dusty due to powder formation under dynamic wheel loads. (4) It should be reasonably elastic. (5) It should have resistance to abrasion and weathering (6) It should be non-porous to provide durability to the ballast. (7) It should hold the sleepers laterally and longitudinally under all conditions traffic, especially on the curves. (8) It should be able to facilitate easy drainage to rain water. (b) Functions of Ballast The main functions of ballast of a railway track are as under: (1) It provides a hard and level bed for the sleepers. (2) It holds the sleepers in proper position during the passage of moving trains. (3) It provides to some extent an elastic bed for the track. (4) It transmits and distributes the moving load of the trains from the sleepers to the formation uniformly. (5) It protects the formation surface from direct exposure to sun, rain and frost. (6) It provides a proper drainage to the track, keeping the sleepers in dry condition. (7) It obstracts the growth of vegetations at the track formation. (8) It provides proper super elevation to the outer rail on curves. (9) It provides an easy means for correcting the unevenness of the track. (10) It provides the lateral and longitudinal stability to the track (11) It protects the sleepers from capillary moisture of formation. (12) It provides a media for absorption of all impacts caused by rolling stock. 18. What is ballast? Why is ballast used for in the railway track? Write briefly on the different types of ballast used. Solution Ballast The material used as an elastic cushion between the sleeper and the top of he formation, is called ‘Ballast’
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Types of Ballast Keeping in vies the availability, workability, durability and strength of the ballast different materials have been used as ballast. The most important types of ballast materials used in. (1) Broken stones (2) Gravels (3) Sand (4)Moorum (5) Cinder (or ash) (6) Brick bats (7) Kankar (8) Ballast earth. Ballast Size The broken stones either of too big size or too small size are found unsuitable for railway ballast. The size of ballast depends upon the type of sleeper, method of maintenance and the location of the track. The ballast which contains stones varying in size from 20 mm to 50 mm with reasonable proportion of intermediate sizes, is considered a best ballast for obtaining better interlocking. Accordingly, the following sizes have been recommended on India railways. 1. for wooden sleeper tracks ….. 50 mm 2. for steel sleeper tracks ….. 40 mm 3. for points and crossings ….. 25 mm Sub-Ballast and Blanket Sub-ballast: A layer of suitable material interposed between the stone ballast and the formation soil is called sub-ballast. Function of sub-ballast: The function of eh sub-ballast is to distribute the loads of the rolling stock more evenly and over lager area of the formation soil. Blank: The layer of a suitable material provided on the top of a poor formation is called a blanket. Functions of blanket: The functions of a blanket are: (1) It improves the bearing capacity of the formation. (2) It avoids interpenetration of ballast and the soil. (3) It avoids the formation of ballast pockets. (4) It prevents the bottom soil to heave up and thus avoids mud pumping conditions. (5) It safely drains off water from the top ballast. CHAPTER 7 RAIL FIXTURES AND FASTENINGS 20. (a) List the various types of fixtures and fastenings in a permanent way. (b) Describe the functions of fish plates in a rail joint Solution (a) The various types of rail fixtures and fastenings commonly used in a permanent way are the following: 1. Fish plates 2. bolts 3. Spikes 4. Chairs 5. Keys, cotters and tie bars 6. Bearing plates 7. Guard rails 8. Check rails 9. M.C.I. insert
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10. Rubber pads (b) Functions of the fish plates The main functions of fish plates are as under. (1) They keep the rail section in vertical and horizontal plane so as to maintain continuity of rails. (2) They allow free longitudinal movement of rails. (3) They provide the necessary expansion gap at the joint. (4) They provide the stability and strength to the rail joint. (5) They support the underside of the head of rail and top of the foot of rail. (6) They resist the stresses due t lateral and vertical bending movements without getting distorted. (7) They absorb the shock caused by the jumping of the wheel over the expansion gap. 21. Explain briefly the following. a. Spikes and Chairs b. Keys, Cotters and Tie Bars c. Bearing Plate d. Check Rails and Guard Rails e. M.C.I Inserts and Rubber Pads Solution (a) Spikes Spikes are used for fixing the rails on sleepers with or without bearing plates below the rails. A good spike should hold the rail properly so as to obtain perfect gauge. It should also be strong enough t resists the motion of the rails. It should be cheap and of such a design the fixing and removing it, is easy. The various types of spikes commonly used on Indian Railways are: (1) Dog spikes (2) Screw spikes (3) Round spikes (4) Elastic spikes. Chairs Chairs are used for holding double headed (D.H) and bull headed (B.H) rails on the sleepers with proper gauge. The chairs are invariably made of cast iron and they distribute the load from the rail on the sleeper through their flat bottoms. (b) Keys, Cotters and Tie Bars Key: A small tapered piece of wood or metal, which is used to fix a rail to the chair, is known as a key. The following types of metal keys are in common use: (1) Stuart’s key (2) Morgan key (3) Coiled key Cotters: The cotters are used for fixing the tie bars with cast iron sleepers. A cotter is a wedge shaped mild steel plate with a split in either horizontal or vertical plane. Cotters
M.S Tie Bars: Mild steel tie bars are used for connection and holding the pots or bowls together.
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(c) Bearing Plates The rectangular plates made of either mild steel, cast iron, wrought iron, or malleable steel which are interposed between the foot of a flat footed rail and wooden sleeper to distribute the load on a larger area, are called bearing plates. The bearing plates are required not only to distribute the load but also to reduce the rubbing acton of the rail seat on the sleeper. These also limit the compressive stresses on the sleeper. The friction between the bearing plate and the sleeper reduces the lateral forces on the spike and thus these help to improve the gauge holding capacity of the sleeper. (d) Check Rails The rails, which are introduced along the inner rail of a track on sharp curves for reducing the wear of rails, are called ‘check rails’. Check rails are also provided along the straight rails opposite the crossings in turnouts Guard Rails The rails, which are provided on bridges of long spans with open floor, parallel to the running rails in order t prevent derailed wheels from falling off the bridge, are called guard rails. These are fastened to sleepers at a fixed distance apart from either running rail in inter rail space. Guard rails are also provided on level crossing to provide a path way clearance to the running wheels. (e) M.C.I Insets The Malleable Cast Iron (M.C.I) inserts are fixed into the concrete during their manufacturing process. The inserts are of two types: (1) Stem type M.C.I.: These inserts are used in normal pretensioned concrete sleepers. The weight of the system insert is 1.6 kg per piece. (2) Gate type M.S.I. insert: These inserts are used in post-tensioned concrete sleepers. The approximate weight of gate type M.C.I. insert is 1.7 kg per piece. Rubber Pads A rubber pad is interposed between the food of rail and concrete sleeper. The main functions of a rubber pad are: (1) It dampens and absorbs the vibrations of the rail. (2) It easily absorbs the shocks. (3) It resists the lateral movement of the rail. (4) It prevents abrasion of the rail bottom surface. (5) It provides good electrical insulation for an electrified track. CHAPTER 8 GEOMETRIC DESIGN OF TRACK 22. (a) What do you understand by the following terms for the section of the track. i. Grade compensation on curves ii. Widening of gauge (b) List the various types of gradients that are adopted in laying a railway track. Solution (a) (i) Grade compensation
Whenever a train is pulled along a curve, an additional tractive force is required. The ruling gradient is the maximum gradient on a particular section of the track. If a curve lines on a ruling gradient, the total resistance due to the 22
gradient and curvature will exceed the ruling gradient. In order to avoid the total resistance beyond the permissible ruling gradient, the gradients are reduced on curves. This reduction in gradient is known as grade compensation on the curves. The curve resistances are generally expressed as a percentage per degree of a curve. B.G.track ….. 0.04% per degree M.G. track ….. 0.03 5 per degree N.G track …..0.02% per degree (ii) Widening of gauge on Curves
Due to impounding action of the wheels on curves, the gauge of the track gets widened and the rails get tilted outward. To prevent the tendency of tilting the rail outward the gauge of the track on curves is suitably widened. The amount of widening of gauge depends on the radius of the curve, gauge and rigid wheel base of the vehicles. The most common formula used fro determination of extra width of gauge is: d
( B L ) 2 x125 R
where d = extra width of gauge in mm. B = rigid wheel base in meters R = radius of the curve in meters L = lap of the flange in meters
2 ( D h)h
where D = diameter of wheel in mm H = depth of wheel flange below top of the rail Note. The following points may be noted. (i) The extra width of gauge should not exceed 25 mm for B.G. tracks and 16 mm for M.G. tracks. (ii) The general practice on Indian Railways is not to width the gauge on curves less than 4 ½º (b) Various Types of the Gradients
(1) (2) (3) (4)
Ruling gradients Momentum gradients Pusher gradients Gradients in station yards.
23. What are the elements of a simple circular curve? Solution Elements of a Simple Curve 1. Back tangent. The tangent T 1 I at T1, the point of commencement of the curve, is called “back tangent”.
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2. Forward tangent. The tangent I T 2 at T2, the end point of the curve, is called ‘forward tangent’. 3. Point of intersection. The point I where back tangent when produced forward and the forward tangent when produced backward interest, is called the point of intersection. 4. Angle of intersection. The angle between the back tangent I T 1 and the forward tangent I T2 is called the angle of intersection of the curve. 5. Angle of deflection. The angle through which forward tangent deflected is called angle of deflection of the curve. It may be either to the either to the right or to the left, it is generally denoted by. 6. Point of commencement. The point T 1 where the curve originates from the back tangent is called the point of commencement of the curve. It is also sometimes known as point of the curve. 7. Point of tangency. The point T 2 where the curve joins the forward tangent is called point of tangency. 8. Deflection angle to any point on the curve. The angle between the back tangent and the chord joining the point of commencement t that point on the curve, is called deflection angle of the point. The deflection angle to the point A on the curve is I T 1 A which is generally denoted by δ. 9. Tangent distance. The distance between the point of intersection and point of commencement of the curve or distance between the point of intersection and point of tangency, is called the tangent. 10. Length of the curve. The total length of the curve from the point of commencement to the point of tangency is called length of the curve. 11. Long chord. The chord joining the point of commencement and point of tangency is called long chord. 12. Mid-ordinate. The ordinate joining the mid point of the curve and long chord is called long chord. 13. Normal chord. A chord between two successive regular pegs on the curve is called a normal chord. 14. Sub-chord. When a chord is shorter than the normal chord. It is called a ‘sub-chord’. These sub-chords generally occur at the beginning and at the end of the curve. 24. (a) A five degree curve diverges from a main curve of 4º in an opposite direction in the layout of a B.G. yard. If the speed on the main curve is restricted to 54.53 kmph, determine the speed restriction on the branch line. Assume permissible cant deficiency as7.5 cm. (b) What do you understand by cant deficiency? If an 8º curve track diverges from main curve of 5’ in an opposite direction in the layout of a B.G. yard, calculate the super elevation and the speed on branch line, if the maximum speed permitted on the main line is 45 kmph. Solution (a) Radius of the main line curve 1750 437.5m 4
Equilibrium cant for a speed of 54.53 kmph GV 2 e 1.27 R
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1.676 x54.53 x54.53
1.27 x 437.5 = 8.97cm Actual super elevation on the main line track = Equilibrium cant - cant deficiency = 8.97-7.5 = 1.47 cm Max. Negative cant on the branch line = -1.47cm Theoretical super elevation on the branch line = Negative cant + cant deficiency = -1.47+7.5= 6.03 cm Restricted speed on thr branch line may be obtained from the equation GV 2 6.03 1.27 R 6.03 x1.27 x350 2 V 1.676 =1599.2452 V = 39.99 say 40kmph. Ans.
(b) The cant deficiency may be defined as the difference between the cant necessary for the maximum permissible speed on a curve and the actual cant provided. Higher cant deficiency causes more unbalanced centrifugal force and discomfort to the passengers. G = 1.676 cm V = 45 kmph 1750 R m 5 Equilibrium cant on main line curve 2
e
GV
1.27 R 1.676 x 45 x 45 x5
7.635cm 1.27 x1750 Assume a permissible cant deficiency on B.G. track = 7.6 cm Actual cant to be provided on main track = Equilibrium cant-deficiency = 7.635-7.600 = 0.035 cm Negative cant on branch line =-0.035 cm. Ans. Theoretical cant on the branch line track = negative cant + cant deficiency = -0.035 + 7.600 = 7.565 cm. Let V be the restricted speed on the branch line 1.676 xV 2 x8 1750 asR m 7.565 1.27 x1750 8 4.565 x1.27 x1750 V 2 1253.9686 1.676 x8 Vmax on the branch line = 35.4 kmph. Ans.
25. (a) Explain why super elevation is necessary on a curve alignment. (b) Explain briefly types of classification of horizontal curves.
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Solution (a) Super Elevation When a vehicle negotiates a curve, it is subjected to a constant radial acceleraton which produces centrifugal force acting horizontally at the centre of gravity of the vehicle, radially away from the centre of the curve. In order to counteract this force, the outer rail of the track is raised slightly higher than the inner rail. The difference in elevation between the outer rail and inner rail is called super elevation or cant. (b) Classification of Horizontal Curves Horizontal curves are classified as under: (1) Simple curves (2) Compound curves (3) Reverse curves (4) Transition curves. (1) Simple curves: The horizontal curve which consists of a single are of a circle, is called a simple curve of simple circular curve. Simple circular curves are designated either by their degree of radius. They are inserted between two straights or between two transition curves. (2) Compound curves: The horizontal curve which consists of two or more arcs of different circles with different radii, having different centers on the same side of the common tangent and bending in the same direction, is called a compound curve. (3) Reverse curves: The horizontal curve, which consists of two arcs of different circles of same or different radii, bending in opposite directions with a common tangent at the junction, is called a reverse curve. (4) Transition curves: The horizontal curve of varying radii introduced between a straight and a circular curve, is called a transition curve. A transition curves is also known as curve of easement. The radius of a transition curve varies from the infinity at its beginning to a definite minimum value at the junction of the circular curve. CHAPTER 9 POINTS AND CROSSINGS 26. Write short notes in the followings: i. Left hand and right hand turn outs ii. Theoretical nose of crossing and Actual nose of crossing iii. Splice rails and Wing rails iv. Point rails and Stock rails v. Tongue rails and Stretcher bar Solution i. Left hand turnout: The turnout which diverts the trains to the left, is called a left hand turnout. Right hand turnout: The turn out which diverts the trains to the right, is called a right hand turn out. ii. Theoretical nose of crossing (T.N.C). the point of intersection of the gauge faces of the point rail and splice rail of a crossing, is called the theoretical nose of crossing. It is slightly away from the actual nose of the crossing. Actual nose of crossing (A.N.C.). The ends of the point rail in the gap of the crossing is called actual nose of the crossing
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iii. Splice rail. The rail of the V-shaped portion of the crossing I,e frog, which ends a little behind the nose of crossing is called splice rail. Wing rail. The two bent up rails of the crossing which are connected to the ends of the crossing lead rails (one straight and one curve rail) are called the wing rails. iv. Point rail. The rail of the V-shaped portion of the crossing i.e. frog, which ends at the nose of crossing, is called point rail. Stock rails. The rails of the main line track against which tongue rails snugly fit, are called stock rails. v. Tongue rails. The tapered rails whose thicker ends known as heel are fixed to the main track an thinner end known as toe of the switch to obtain a snugfit with the respective stock rails, are called tongue rails, switch rails or point rails. By moving the tongue rails, the flanged wheels of the trains are diverted from one track to the other. Stretcher bars. Two or three bars which are used to connect the ends of the tongue rails at the toe to ensure the movement of both the tongues through the same distance, are called stretcher bars. 27.(a) On a straight B.G. track, a turnout takes off as an angle of 6º 42’ 35” Angle of switch = 1º 34’ 27” Length of switch rail = 4.37 m Heel divergence = 11.43 cm Length of straight arm = 0.85 m. Determine the radius and the crossing lead. (b) A 1 in 12 turn out is to be provided on a B>G> straight track, calculate (i) radius of the curve lead rail (ii) lead distance, and (iii) over all length of the turn out. Data given: Heel divergence = 133 mm Actual length of switch rail = 6001 mm Theoretical length of switch rail = 6743 mm Distance between toe of crossing and theoretical nose of crossing = 2415 mm Distance between toe of crossing and theoretical nose of crossing = 1498 mm Distance between theoretical nose of crossing and heel of crossing = 3810 mm Solution (a) As the length of straight arm (h) is given, the second method of design will be adopted Given: G = 1.676m d = 0.1143 m h = 0.85 m α = 6º 42’ 35” β = 1º 34’ 27” G d h sin Ro cos cos Ro
1.676 0.1143 0.85 sin 642'35"
cos 134'27" cos 642'35" 225.96m
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R R0
G
2
225.96
1.676
2 225.12m Ans. cross in lead (G d h sin ) cot
2
h cos
(1.676 0.1143 0.85 sin 642'35" ) cot
21.08m Ans.
6 42' 35"1 34' 27" 2
0.85 cos 6
(b) From the given data, it is seen that the design is to be done by Method No.2 4 45' 49" For 1 in 12 turnout Let β be the angle of switch heeldivergence 133 0.0197 sin theoretical length of switch rail 6743 β = 1º 7’ 49” Ro
G d h sin
cos cos 1.676 0.133 2.415 sin 4 45' 49" cos 1 7' 49" cos 4 45' 49"
412.09
R=412.09-0.838=411.252m Ans. Or Crossing lead = (G-d-h sin α)cot α + β/2+h cos α L=1.343cot 2º 56’ 49”+2.415cot 4º 45’ 49” =28.495m Ans. Over distance = Distance between heel of crossing and T.N.C. + lead distance + actual length of switch rail + distance between actual toe of switch and end of stock rail. = 3.810 + 28.495 + 6.001 + 4.498 Over length = 39.804 m. Ans. CHAPTER 10 TRACK MAINTENANCE 28. Describe the followings: i. Necessity of track maintenance ii. Essentials of good track maintenance iii. Advantages of proper track maintenance
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42' 35"
Solution i. Necessity of Track Maintenance The track maintenance is carried out for the following purposes: (1) As a newly laid railway track settles slowly under moving train loads, the maintenance gangs are employed to bring the embankment to the proper formation level. (2) Due to constant movement of heavy and fast moving trains, the packing under sleepers gets loose and thus the geometry of the track gets disturbed. The gauge, alignment longitudinal and cross levels also get affected adversely, Hence, the maintenance gangs are required regularly to rectify these defects as and when these occur. (3) Due to vibrations and impact of the fast moving trains, railway track fittings get loose and a heavy wear and tear of track occurs. This necessitates regular inspection and maintenance of the track. (4) Maintenance is also required to replace the track and its components as and when these wear and tear due to natural weathering agents such as sun, sand and rain water. ii. Essentials of Good Track Maintenance A well maintained track should have the following characteristics: (1) The correct gauge is within specified limits. (2) Longitudinal levels are uniform. (3) The cross levels are same except on curves where difference in cross levels is equal to the desired super-elevation. (4) Along straights, the alignment is perfectly linear. (5) There is a sufficient quantity of ballast bed. (6) The sleepers are well packed. (7) The formation is well maintained with good track drainage for disposal of rain water. (8) The components of all fittings are in the good working condition. Defective or badly worn and torn components are replaced at an earliest opportunity.
iii. Advantages of Proper Track Maintenance The advantages of a well maintained track are as under: (1) A well maintained track provides safe and comfortable journey to passengers. If the track is not maintained properly, there will e discomfort to the passengers and some times, there may be a derailment of vehicles, causing accidents and consequently loss of lives and property. (2) Proper maintenance of track increases the life of track as well as that of the rolling stock. (3) Good track maintenance helps in reducing the fuel consumption and cost of operation. (4) Maintenance of track fittings at proper time avoids the loss of the items and thus, it affords considerably economy. (5) Track maintenance, if ignored for a long time may result in heavy track renewals, costing a huge expenditure. 29. Calculate the necessary data for setting out a semi permanent diversion 20 m away from the B.G. track. Assume: radius of the curves = 440 m Gradient along diversion = 1 in 100 Straight proportion of diversion = 50 m Straight length between reverse curve = 30.5 m.
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Solution Given data: d = 20m; R = 440 m c = 30.5 m; S = 50 m Calculation of the length L, S L 4 Rd c 2 d 2 2 = 214.02m Total length of diversion along main track = 2x214.02 = 428.04 m. Ans.
Calculation of tangent length Rd 40.09 m Ans. t S L c 2 Total diversion length along curve = 8t+2c+s = 8x40.09+2x30.05+50 = 431.72 m Ans. Length of offset, O = (formation width +gauge)/2 6.10 1.676 3.888m 2 Length of diversion on the existing track formation a 2OR 2 x3.888 x 440 58.49m. Ans. Length of diversion along which grade is to be provided = (4t + c-a) = 4 x 40.09 + 30.5-58.49 = 160.36 + 30.5-5849 = 132.37 m Grade permitted is 1 in 100, i.e. 1% Compensation for 1750/440 degree curve say 4º = 4 x 0.04 = 0.16% Compensated grade = 1-0.16 = 0.84% Maximum lowering of bank = (132.37 x 0.84)/100 = 1.11 m. Ans. 30. Design the layout of a 2 m high BG semi permanent diversion for rebuilding a 4 x 6.1 m bridge on 4 m high line track. Adopt economical specifications. Solution
Assumptions Radius of curves = 440 m (approximately 4º curve) Straight length between reverse curves = 30.5 m Gradient = 1% Grade compensation = 0.04% degree of curve Given: High of main bank =4m High of diversion bank = 2m Calculations: Difference in high of bank = 4-2 = 2 m Minimum value of S = 30.5 + 4 x 6.1 + 30.5 = 85.4 say 86 m minimum distance, d = 2x4 +2 x 2 + 6.10 = 18.10 m
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