21st BCS Civil Engineering Written Questions and Solve–


Transportation Engineering:

Question-1: a) Write down the function of ballast in a railway track?


What is Ballast?

Ballast is the foundation of railway track and it distributes the load to the underlying layers in a railway track.Generally rocks or gravels are used as a ballast material.The gravels covers the sub-grade of railway track and distributes the load the underlying layers.

Functions of Ballast:

  • To provide a hard layer for the sleepers to rest on.
  • To distribute the loads.
  • For easy maintenance of railway track without disturbing the underlying layers.
  • To prevent the growth of plants and vegetation etc.
  • To hold the sleepers in position during the train passing.
  • To maintain the lateral stability of the railway track.
  • To ensure proper drainage of water.

Question:1(b)–Define Yard.Discuss the important points needs to be considered in designing the Marshalling Yard.



A yard is a space/area that contains a complex series of railroads, tracks and also contains sheds for maintaining,repairing storing,joining of rail coaches and locomotives.

Marshall Yard are of three types:

  • Hump Yard
  • Gravity Yard
  • Flat Yard

Important factors to be considered during designing of Marshalling yard:

(If anyone know please contribute the answer of this section in comment box)

Question:1(c)–Design the rate of super-elevation for a curve of radius 400 m and speed of 80 km/hr. Also check the co-efficient of lateral friction.(G.C. Singh,pp-167)


For mixed traffic conditions super-elevation, e=(0.75V)^2/127R = (0.75X80)^2/(127X400) = 0.0708 = 1 in 14.12

check for co-efficient of lateral frictions,  = (V^2/127R)- 0.067 = (80^2/127X400)-0.067 = 0.059

As the value is less than 0.15 the safe value,the design in safe with a super-elevation of 1 in 15 (answer).