Tuesday, January 7, 2014

One liners - Transportation Engineering for GATE, PSUs - Part 10

Hello there,
How have you been? Here is another round of one liners for your preparation for the GATE and PSUs examinations.

  • Ratio of width of the car parking area required at kerb for 30 degree parking relative to 60 degree parking is approximately 0.5
  • Load carrying capacity of rigid pavements depends more on the properties of concrete than strength of sub-grade.
  • Compared to flexible pavements, rigid pavements are more affected by temperature variations.
  • Collision diagrams are used to study accident pattern and determine remedial measures.
  • Emergency escape ramp is provided in down grades of a highway.
  • Plasticity index of the fraction passing 425 micron IS Sieve in case of sub-base or base course would be less than 6.
  • If the CBR value obtained at 5 mm penetration is higher than that at 2.5 mm, then the test is repeated for checking; and if the check test reveals a similar trend, then the CBR value is to be reported as higher value obtained at 5 mm penetration.
  • Road construction/design in chronological sequence : Tresaguet, Telford, Macadam & C.B.R.
  • The general requirement in constructing a reinforced concrete road is to place a single layer of reinforcement near the top of the slab.
  • It is a common practice to design a highway to accommodate the traffic volume corresponding to 30th hour.
  • The amount of mechanical energy imposed on the aggregate during the aggregate impact test is of the order of (15*14*38 kg-cm) 7980 kg-cm.
  • For wet and cold climates emulsions are recommended to be used as binders.
  • With reference to Marshall mix design criteria for highways, Stability value = 340 min.; Flow value = 8-16 & % air voids = 3-5.
  • For the design of valley vertical curve, the design criteria used are rider comfort, headlight sight distance and drainage.
  • Bird baths may be formed as the deformations which may be caused by localized or variable sub-grade failure.
  • Pot holes A steep sided, bow-shaped cavity caused by the loss of surfacing as well as base course erosion.
  • Ravelling is the removal of larger surface aggregates leaving craters.
  • Subsidence is abrupt lowering of the road surface due to poor drainage.
  • For carrying out bituminous patch work during the rainy season, the most suitable binder is bituminous emulsion.
  • The characteristic rebound deflection on a pavement, using Benkelman beam study is used by IRC to suggest the equivalent overlay design thickness.

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