Friday, January 3, 2014

One liners - Transportation Engineering for GATE, PSUs - Part 7

Hello there,

How have you been? Here is another round of one liners for your preparation for the GATE and PSUs examinations.
  • Bottom-most layer of a pavement is called Sub-grade.
  • Flexible pavement distribute the wheel load through a set of layers to the sub-grade.
  • The number of repetitions, which the pavement thickness designed for a given wheel load should be able to support during the life of a pavement is 1000000.
  • Group Index Method of design of flexible pavement is an empirical method based on physical properties of sub-grade soil.
  • Minimum and maximum values of a Group Index can be 0 and 20 respectively.
  • If the Group Index value of sub-grade is between 5 to 7, then sub-grade is treated as poor.
  • Tyre pressure influences the quality of the surface course.
  • Rigidity factor for a tyre pressure greater than 7 kg/cm2 is less than 1.
  • In a dual wheel assembly if P is equal to each wheel load, S is centre to centre distance of dual wheels and d is the distance between walls of wheels, then total stress due to the dual wheels at any depth greater than S is equivalent to a single wheel load of magnitude 2P.
  • Main drawback of CBR method is that it gives the total thickness which remains same irrespective of the quality of materials used in the component layers.
  • Critical load positions in a rigid pavement design is taken as interior, edge and corner loading.
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