Pavement Design Factors - IES Previous Year Questions
1. The number of load cycles (Nf) to cause the failure of a pavement is proportional to (P is the respective applied load) _____ .
[IES 1997]
- P-4
- P2
- P-1
- P4
Answer: Option C
Explanation:
If pavement structure fails with N1 number of repetitions of P1 load and similarly if pavement structure fails with N2 number of repetitions of P2 load, then P1N1 and P2N2 are said to be equivalent.
P1N1 = P2N2
⇒ PNf = Constant
⇒ Nf =
⇒ Nf ∝
Explanation:
If pavement structure fails with N1 number of repetitions of P1 load and similarly if pavement structure fails with N2 number of repetitions of P2 load, then P1N1 and P2N2 are said to be equivalent.
P1N1 = P2N2
⇒ PNf = Constant
⇒ Nf =
Constant / P
⇒ Nf ∝
1 / P
2.  Which of the following factors have to be considered for the design of the flexible pavement for a highway ?
- Design wheel load
- Strength of pavement component material
- Expansion joints
- Climatic factors
Select the correct answer using the codes given below:
[IES 2005]
- 2, 3 and 4
- 1, 3 and 4
- 1, 2 and 4
- 1, 2 and 3
Answer: Option C
Explanation:
The design of flexible pavement depends on
Explanation:
The design of flexible pavement depends on
- Design wheel load
- Subgrade soil
- Climatic factors
- Pavement component materials
- Environmental factors
3.  What is the deflection at the surface of a flexible pavement due to a wheel load of 40 kN and a tyre pressure of 0.5 MPa ? The value of E for pavement and subgrade is 20 MPa.
[IES 2014]
- 11 mm
- 9 mm
- 6 mm
- 15 mm
Answer: Option C
Explanation:
The displacement at the surface of flexible pavement as per Burmister method is given by,
∆ =
where,
p - contact pressure = 0.5 MPa
a - radius of contact area
Es - Young’s modulus of subgrade = 20 MPa
F2 - factor depending on
Now, contact area =
⇒ π x a2 = 80 x 103
⇒ a = 159.58 mm
Thus, ∆ =
⇒ ∆ = 5.98 mm ≈ 6 mm
Explanation:
The displacement at the surface of flexible pavement as per Burmister method is given by,
∆ =
1.5 pa / Es
x F2 where,
p - contact pressure = 0.5 MPa
a - radius of contact area
Es - Young’s modulus of subgrade = 20 MPa
F2 - factor depending on
Modulus of elasticity of subgrade / Modulus of elasticity of pavement
and Depth / Radius
. Assume F2 = 1Now, contact area =
Wheel load / Tyre pressure
= 40 x 103 / 0.5
= 80 x 103 N/mm2⇒ π x a2 = 80 x 103
⇒ a = 159.58 mm
Thus, ∆ =
1.5 pa / Es
x F2 = 1.5 x 0.5 x 159.58 / 20
x 1 ⇒ ∆ = 5.98 mm ≈ 6 mm
4.  Which one of the following statements is correct ?
[IES 2020]
- The ratio of load on the wheel to contact pressure is called as rigidity factor.
- The value of rigidity factor is more than three for an average tyre pressure of 7 kg/cm2.
- Rigidity factor does not depend upon the degree of tension developed in walls of tyres.
- The ratio of load on the wheel to contact area or area of imprint is called as contact pressure.
Answer: Option D
Explanation:
Explanation:
- The ratio of contact pressure to tyre pressure is called the rigidity factor.
- The value of rigidity factor is 1.0 for an average tyre pressure of 7 kg/cm2.
- The rigidity factor depends upon the tension developed in the walls of the tyres.
5.  The thickness design of pavement mainly depends on _____ .
[IES 2022]
- The climatic factors
- The design wheel load
- The subgrade soil
- The pavement materials
Answer: Option B
Explanation:
Design wheel load is the primary factor to be considered while designing the thickness of a pavement. Higher the wheel load thicker is the pavement to be provided. The design of flexible pavement depends on
Explanation:
Design wheel load is the primary factor to be considered while designing the thickness of a pavement. Higher the wheel load thicker is the pavement to be provided. The design of flexible pavement depends on
- Design wheel load
- Subgrade soil
- Climatic factors
- Pavement component materials
- Environmental factors