Rigid Pavement Design - IES Previous Year Questions

21. The corrected modulus of subgrade reaction for standard diameter plate is 6.0 kg/cm3. What would be the modulus of subgrade reaction of the soil when tested with a 30 cm diameter plate ?

[IES 2013]

  1. 25 kg/cm3
  2. 30 kg/cm3
  3. 60 kg/cm3
  4. 15 kg/cm3
Answer: Option D
Explanation:
The modulus of subgrade reaction is calculated using the standard plate of diameter 75 cm.
As per Burmister method,
Δ =
1.18 pa / Es
x F2
⇒
p a / Δ
=
Es / 1.18 F2
= constant
⇒ K a = constant {Since, p/Δ = K}
⇒ K1 a1 = K2 a2
⇒ K2 =
6 x 75 / 30

⇒ K2 = 15 kg/m3
22. What is the critical thickness of a prestressed concrete pavement (using Westergaard’s corner load formula) to support a maximum wheel load of 4200 kg? Allow 10% for impact. Tyre pressure may be taken as 7 kg/cm2. Assume flexural strength of concrete as 50 kg/cm2, factor of safety as 2, subgrade reaction for plastic mix road as 6 kg/cm3 and modulus of elasticity as 3 x 105 kg/cm2.

[IES 2016]

  1. 21.6 cm
  2. 23.6 cm
  3. 25.6 cm
  4. 19.6 cm
Answer: Option D
Explanation:

23.  Consider the following statements regarding pavements:

  1. Rigid pavements are more suitable than flexible pavements for stage construction.
  2. Rigid pavements are more affected by temperature variations than flexible pavements.
  3. In a flexible pavement, any deformation in the top layers is transferred to underlaid layers; but, in rigid pavements, there is slab or beam action due to which any deformation is only in the top layer of the concrete slab. 

Which of the above statements are correct ?

[IES 2017]

  1. 2 and 3
  2. 1 and 3
  3. 1, 2 and 3
  4. 1 and 2 only
Answer: Option A
Explanation:
IRC 37: 2012 Clause 4.3.3 suggests that in case of cemented bases and sub-bases, stage construction may lead to early failure because of high flexural stresses in the cemented layer and therefore, not recommended. Hence, rigid pavement are not suitable for stage construction.

24.  Which one of the following is not the correct type of critical load position in pavement slab design for the load on the pavement surface ?

[IES 2020]

  1. Edge loading
  2. Eccentric loading
  3. Corner loading
  4. Interior loading
Answer: Option B
Explanation:
The critical load positions considered for the analysis of stresses in cement concrete pavement are interior, edge and corner regions.

25.  Which of the following statements are correct regarding Westergaard’s concept for temperature stresses ?

  1. During the day, the top of the pavement slab gets heated under the sunlight when the bottom of the slab becomes hot. 
  2. During summer season as the mean temperature of the slab increases, the concrete pavement expands towards the expansion joints. 
  3. Due to frictional force at the interface, compressive stress is developed at the bottom of the slab as it tends to expand.

[IES 2020]

  1. 2 and 3 only
  2. 1 and 3 only
  3. 1, 2 and 3 
  4. 1 and 2 only
Answer: Option A
Explanation:
During the day, the top of the pavement slab gets heated under the sunlight when the bottom of the slab remains relatively colder.

26.  Consider the following statements related to road pavements:

  1. Deflections measured near cracks are normally much lower than the measurements in non-distressed areas.
  2. Deflection measurements near longitudinal joints, transverse joints or corners are higher than those measured at mid-slab for concrete pavements. 
  3. Thermal and moisture gradient in the vertical direction of concrete slabs does not have any influence on deflection measurements.
  4. Measurements taken at night or in the early morning are considerably different from those obtained in the afternoon.

Which of the above statements are not correct ?

[IES 2021]

  1. 1 and 3 only
  2. 2 and 4 only
  3. 1 and 2 only
  4. 1, 2 and 4 only
Answer: Option A
Explanation:
  • Deflections measured near cracks are normally much higher than the measurements in non-distressed areas.
  • Thermal and moisture gradients in the vertical direction of concrete slabs influence the deflection measurements of the pavement.
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