# Pavement Design Questions and Answers – Flexible Pavement Design

This set of Pavement Design Multiple Choice Questions & Answers (MCQs) focuses on “Flexible Pavement Design”.

1. Which of the below is a type of empirical methods used for the design of flexible pavements?
a) Group index method
b) Burmister method
c) Triaxial test
d) IRC method

Explanation: The methods used for the design of flexible pavement can be broadly classified as empirical, semi-empirical, analytical and mechanistic-empirical methods. The group index method comes under the empirical method used for flexible pavement design.

2. ______ are pavements used to divert traffic onto it until a new pavement has been provided.
a) Diversions
b) Drivethroughs
c) Detours
d) Dipaves

Explanation: Whenever a new pavement is being constructed or an existing pavement is being reconstructed, the traffic is diverted onto another pavement temporarily. These types of pavements are called detours.

3. What are the two failure criteria used for the mechanistic-empirical method?
a) Cracking and fatigue
b) Shrinkage cracking and fatigue cracking
c) Rutting and shrinkage cracking
d) Fatigue cracking and rutting

Explanation: For a mechanistic-empirical design process, two types of failure criteria are widely used. One criterion is related to fatigue cracking and the other is related to rutting in the subgrade.

4. The design method for flexible pavements is not based on which of the below options?
b) Soil strength
c) Soil classification
d) Aggregate strength

Explanation: It has not been able to establish a rational method for the design of flexible pavements. Therefore, methods based on soil classifications, soil strength and subgrade support have been used. It is based on the experience and past data available.

5. The semi-theoretical method of flexible pavement design is based on ______
a) Stress-strain function
c) Mathematical model

Explanation: The semi-theoretical method of flexible pavement design is based on the stress-strain function and are modified according to experience. Empirical methods are based on subgrade properties and strength.

6. The disadvantage of using a mechanical-empirical pavement design method is that it cannot be used for pavement rehabilitation design.
a) True
b) False

Explanation: Using the mechanical-empirical method, it is possible to design new pavement as well as design the rehabilitation of existing pavement. It is considered to be an advantage of using this method for analysis and design.

7. Which mechanistic model is commonly used to design pavement?
a) Dynamic
b) Viscoelastic
c) Layered elastic
d) FEM

Explanation: There are many mechanistic models available today. They include dynamic, viscoelastic, layered elastic and FEM. Out of these models, the layered elastic model is used commonly because the flexible pavement is supposed to be made up of a number of layers.

8. Which of the below is not an input for the design of flexible pavement using the mechanistic-empirical method?
a) Pavement layers thickness
c) Poisson’s ratio
d) Deflection

Explanation: The pavement parameters can be modelled mathematically using the mechanistic models. The inputs for this method include material properties of each layer which are Youngs modulus and Poisson’s ratio, the pavement layer thickness and the wheel load. Stress, strain and deflection are the outputs of the design process.

9. The semi-empirical method is also known as ______
a) Semi-hypothetical
b) Semi-practical
c) Semi-theoretical
d) Semi-factual

Explanation: The semi-empirical method is based on experience and also the stress-strain relations. It is in between the empirical and the theoretical method. Hence, it is also called the semi-theoretical method.

10. Which instrument is used to characterize the in-situ material?
a) Digital CBR apparatus
b) Stabilometer
c) Auto level consolidometer
d) Falling weight deflectometer

Explanation: Falling weight deflectometer is a device that is used to measure the vertical deflection response. The in-situ material indicates the subgrade and the existing pavement. All other options are used to evaluate the properties of the subgrade.

11. Which empirical method is not based on the strength parameter of the subgrade?
a) McLeod
b) Group index
c) CBR
d) Stabilometer

Explanation: Group index is the empirical method based on the subgrade soil classification. McLeod method, Stabilometer and CBR methods are all based on the strength parameter of the subgrade.

12. The California Resistance Value method is a type of which of the below methods used for the design of flexible pavements?
a) Theoretical method
b) Empirical method
c) Semi-empirical method
d) Semi-theoretical method

Explanation: The California Resistance Value method gives the R-value and it is an indication of the stiffness of the material. That test is based on the strength characteristics of the subgrade and hence it comes under the empirical method of design for flexible pavements.

13. The top layer of the pavement must be made of the most superior quality of the material.
a) True
b) False

Explanation: The loads coming on top of the pavement layers is varying from top to bottom. It is the highest at the topmost layer of the pavement and lowest at the bottommost layer. So, the quality of material for the top layer should be very high.

14. What test results is the North Dakota core method based on?
a) Core cutter test
b) Core drilling test
c) Cone density test
d) Cone penetration test

Explanation: The North Dakota core method of design is based on the results obtained from the cone penetration test. North Dakota is a state in the US and the flexible pavements there are designed based on the cone penetration tests results.

15. In how many layers is the perpetual pavement constructed?
a) Three
b) Four
c) Two
d) One

Explanation: The perpetual pavement is a type of flexible pavement that is constructed in layers such that they resist deformations for a longer period of time without maintenance. It consists of three layers – base layer, intermediate layer and wearing surface.

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