Pavement Design Multiple Choice Questions on “Highway Maintenance – Failures in Flexible Pavements – 1”.
1. The ______ of any one of the component pavement layers can lead to the failure of the pavement.
a) Change in width
b) Localized settlement
c) Change in thickness
d) Localized loading
Clarification: The localized settlement due to the loading on the pavement can be detrimental to the pavement layers. The layers get depressed and become unstable due to this. The failure of one pavement layer will result in the failure of the entire pavement.
2. The area surrounding a depression on the pavement surface is generally subjected to ______
Clarification: The flexible pavement is prone to change in its shape because of its flexible nature. So, if there is a depression in the pavement surface, the areas surrounding it would undergo heaving.
3. The ultraviolet rays from the sun make the pavement ______
Clarification: The ultraviolet rays from the sun have the power to oxidise the bitumen coating that is present on top of the pavement. The oxidation makes the pavement surface brittle.
4. Oil spills on the pavement decrease the softening point of bitumen.
Clarification: The parked vehicles can sometimes lead to the leakage of brake fluid or gasoline from them. When these come in contact with the bituminous surface, they tend to increase the viscosity and make it liquidy. Softening point is directly proportional to viscosity, hence it also increases.
5. Which of the below is not a reason for the failure of subgrade?
a) Inadequate stability
b) Lack of lateral confinement
c) Inadequate drainage
d) Excessive stress application
Clarification: Lack of lateral confinement is one of the reasons for the failure of sub-base and not the subgrade. The failure of the subgrade can occur due to inadequate stability, drainage of rainwater and due to the application of excessive stress.
6. Which of the below options is different from the other options?
a) Map cracking
b) Alligator cracking
c) Block cracking
d) Fatigue cracking
Clarification: Map, alligator and fatigue cracking are the different names of the same type of cracks formed on the flexible pavement. While block cracking is a different type of crack formed on the flexible pavement.
7. The wearing of the surface course along the path of the wheel results in ______
a) Shallow rut
b) Deep rut
c) Longitudinal rut
d) Transverse rut
Clarification: The rutting of pavement occurs due to two reasons. One is the repeated application of load along the same wheel path that results in longitudinal ruts. The other is the formation of shallow ruts due to the wearing of surface course along the wheel path. Rutting is always longitudinal.
8. The potholes expand in both width and depth at the same rate.
Clarification: The potholes are formed as small almost round depressions on the pavement surface, which then expand in both width and depth as time passes. Portions of the road start breaking away and result in the enlargement of the pothole. It increases in its width at a rate faster than the depth.
9. What is the main reason for the swelling of the pavement surface?
Clarification: Swelling of the pavement surface is visible as an upward bulge of the surface. This is mainly caused due to the frost action of the subgrade that affects the surface of the pavement. The surface forms small and gradual waves that might later develop into cracks.
10. When does reflection cracking occur?
a) Cement concrete laid over the existing bituminous pavement
b) Vehicle drives over an existing crack
c) Bitumen laid over the existing rigid pavement
d) Same type of cracking occurs in the opposite direction
Clarification: The laying of a bituminous surface course over an existing cement concrete pavement with cracks leads to the formation of reflective cracking. This type of crack is reflected in the same manner on the bituminous surface.