Railway, Bridge & Tunnel Engineering : Question Paper May 2016 - Civil Engineering (Semester 6) | Gujarat Technological University (GTU)
1 Answer

1. a

i) Coning of Wheels

  • The rim or flanges of the wheels are never made flat but they are in the shape of a cone with a slope of about 1 to 20. This is known as coning of wheels.
  • The coning of wheels is manly done to maintain the vehicle in the central position with respect to the track. When the vehicle is moving on leveled track then the flanges of wheels have equal circumference.
  • In any case, when the vehicle is moving along a bended way then for this situation the external wheel needs to cover a more prominent distance then that of internal wheel. Additionally as the vehicle tends to move sideways towards the external rail, the outlines of the ribs of the inward haggle will assist the external wheel with covering a more extended distance than the internal wheel. In this ways smooth riding is created through coning of wheels.

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ii) Creep of Rails

Creep of Rail is characterized as a longitudional development of rail regarding sleeper. Rail tend to slowly move toward predominant traffic. The jerk of rail is normal to all rail line tracks and its worth differs from barely anything sometimes to around 130 mm/month in creep.

There is wide variety in the measure of creep of rail. The chief causes which are answerable for the improvement of creep of rail are talked about underneath.

1. Speed increase or Starting of Train :

At the hour of speed increase, Wheel gives parallel push which causes creep of rail.

2. Deaccelerating or Stopping of Train :

On the off chance that abrupt halting of train happens, slowing down impact will in general push the rail forward and subsequently causes creep forward way.

3. Wave activity or Wave Theory :

As train is passing under the rolls the piece under the moving wheels is packed and discouraged somewhat because of wheel loads. As more the wheel moves this downturn likewise moves and the piece which is under despondency already returns to its unique position.

In addition to this creep of rail may also be caused due to following reasons.

  • Insufficient numbers of sleepers is laid.
  • Uneven spacing of sleepers.
  • Improper expansion joints.
  • Use of improper and faulty sleepers.
  • Rails too light for the traffic carried by them.
  • Poor drainage work.
  • Improper maintenance of track gauge and joints

1. b What is Ballast? Write Function and requirement of good ballast.

Ballast is a granular material which is placed and packed below and around the railway sleepers. Different types of ballast materials used are broken stone, sand, gravel, moorum, brickbats etc. The main purpose of ballast is to transmit the load from sleepers to the formation(consolidated track bed) and to provide drainage facilities to the track.

Function of the Ballast:

  • It gives evened out bed or backing to the rail line sleepers.
  • It moves the heap from sleepers to subgrade and circulates the heap consistently on subgrade.
  • It stands firm on the sleepers in a firm situation while the trains cruise by.
  • It forestalls the longitudinal and sidelong development of sleepers.
  • It offers great seepage to the track.

Requirement of Good Ballast:

  • It ought to be hard and extreme.
  • It ought not be weak and permeable.
  • It ought to have adequate flexibility.
  • It ought to permit simple waste with least spillage.
  • It ought to be wear-safe and tough.

2 (a) Write short note ' Concrete Sleepers'.

  • Substantial sleepers are made by concrete with inside support. Substantial sleepers utilized in numerous nations because of its high solidness and little support.
  • These are more appropriate for fast rails. The majority of the substantial sleepers are produced using pre-focused on concrete in which inward is prompted into the sleeper prior to projecting. Consequently, the sleeper withstand well against high outer tension.

Advantages of Concrete Sleepers

  • They are heavier than any remaining kinds consequently, gives great solidness to the rails.

  • They have long life expectancy in this way, financially ideal.

  • They have great Fire opposition.

  • They are appropriate for a wide range of soil and dampness conditions.

  • Concrete is great encasing thus, this sort of sleepers are more reasonable for circuited tracks.

2 (b) Explain different types of gradient used in railway.

The various gradient used on railway tracks can be classified under the following heads:

a. Ruling Gradient b. Momentum Gradient c. Pusher or Helper Gradient d. Station yard Gradient.

a. Ruling Gradient: The reasonable inclination normally gave in a rail line track is known as the decision angle. It is the greatest inclination permitted on the specific track area. Administering inclination mostly relies on the force of the train.

a. In plain terrain- 1 in 150 to 1 in 200 b. In hilly regions – 1 in 100 to 1 in 150

For the most part, with one train, the accompanying decision slopes are embraced in India.

b. Momentum Gradient: The rising inclination which is trailed by a falling angle and along which trains climb all the more effectively because of force procured by them over the falling slope is called energy slope. Accordingly a force slope can be more extreme than the decision inclination.

c. Pusher Gradient: The rising slope which is more extreme than the decision inclination and along which trains require extra trains to ascend the track is known as the pusher angle. These sorts of angles are vital in uneven territory where more extreme slopes are important to decrease the length of the track.

d. Station Yard Gradient: The base inclination gave on station yard to simple waste is called station yard slope or least angle. In Indian Railways, the greatest inclination allowed in station yards is taken as 1 of every 400 while the base slope suggested for station yards is 1 out of 1000.

2 (c) (i) Cant deficiency

  • The expression "cant deficiency" is characterized with regards to go of a rail vehicle at consistent speed on a steady span bend.
  • Cant itself is a British equivalent word for the super elevation of the bend, that is, the rise of the external rail less the rise of within rail.
  • Cant inadequacy is available when a vehicle's speed on a bend is more prominent than the speed at which the parts of wheel to rail power are ordinary to the plane of the track. All things considered, the resultant power (amassed power of gravitational power and diffusive power) applies the external rail more than within rails, in which it makes sidelong speed increase toward outside of the bend. To decrease cannot lack, the speed can be diminished or the superelevation can be expanded.
  • The measure of cant lack is communicated in term of expected super elevation to be included request to bring the resultant power into balance between the two rails. In the opposite, it is supposed to be "cant abundance" on the off chance that the resultant power applies more against within rail than the external rail, for example, a high super elevation bend with a train going at a low speed.

2 (c) (ii) Negative super elevation

  • Superelevation is the difference in height between the outer and the inner rail on a curve. It is provided to compensate the centrifugal force which causes irregular stressing of rails and other track components Positive when the outer rail on a curved track is raised above the inner rail Negative when the inner rail is raised above the outer rail

  • This is a one of a kind circumstance which happens when the primary line lies on a bend with a branch line turnout of opposite flexure.

  • If the branch-out is on a similar side - comparative flexure, there is no issue of negative cant.

This is a problematic situation where the super elevation fundamental for the normal speed of trains running over the principle line bend can't be given.

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AB - external rail of the fundamental line bend - should be higher than CD Branch line - CF ought to be higher than AE or point C ought to be higher than point A.

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