# Pavement Design Questions and Answers – Mechanical Stabilization – 1

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This set of Pavement Design Multiple Choice Questions & Answers (MCQs) focuses on “Mechanical Stabilization – 1”.

1. The mechanical stabilization of soil does not depend on which of the below?
a) Compaction
b) Consolidation
c) Presence of salts

Explanation: The mechanical stabilization of soil does not depend on consolidation. The major factors affecting the process of mechanical stabilization of soil are mechanical strength of aggregates, gradation, properties of soil, presence of salts and compaction.

2. Which of the below gives the theoretical gradation for maximum density?
a) $$P=100(\frac{D}{d})^n$$
b) $$P=100 (\frac{d}{D})^{1/n}$$
c) $$P=100 (\frac{d}{D})^n$$
d) $$P=100 (\frac{D}{d})^{1/n}$$

Explanation: The right equation for obtaining the gradation for maximum density is given by $$P=100 (\frac{d}{D})^n$$. In the equation, P represents the % finer than diameter d, D is the diameter of the largest particle and n is the gradation index.

3. What is represented in the Y-axis of the distribution curve plotted for Rothfutch’s method?
b) Sieve size
c) Percentage retained
d) Percentage passing

Explanation: Rothfutch method is used for proportioning of the soil. Various grades of soils are mixed together to obtain the most stable mix. A graph is plotted with percentage passing on the Y-axis and sieve size on the X-axis.

4. What proportion of soft aggregates to soil gives the best result?
a) 1:2
b) 2:1
c) 1:1.5
d) 1.5:1

Explanation: The soft aggregates are weak in taking strength, impact and crushing imposed by the heavy loads. So, using mechanical stabilization, it is mixed with soil to make it perform better. The best proportion for the same has been found out as 1-part soft aggregate to 2-parts soil.

5. ______ method can be used when mixing three different materials.
a) Triangular method
b) Rothfutch method
c) Mehra method
d) Tertiary method

Explanation: Triangular method is used to perform proportioning when there are three materials being used. Each material can be designated or classified as coarse aggregate, sand or fine. Then their percentages are marked on the triangular chart and the proportioning can be carried out.

6. What is the gradation index for a spherical shaped particle?
a) 0.5
b) 1
c) 0.3
d) 0.1

Explanation: The gradation index value ranges from 0.3 to 0.5 and it depends on the shape of the particle. The sediment analysis is done on the basis of Stoke’s law, which assumes spherical particles. The gradation index for spherical particles if found to be 0.5.

7. Which of the below is not a typical stage of a mix?
a) No fines
b) Little fines
c) Equal fines
d) Excess fines

Explanation: There are three typical stages of mixes. They are compacted aggregates containing no fines, compacted aggregates with fines filling voids and compacted aggregates with excess fines. There is no stage of an equal amount of aggregate and fines.

8. The method of soil stabilization using soft aggregates was suggested by Fuller.
a) True
b) False

Explanation: The method of stabilization using soft aggregates was formulated by S.R Mehra and it has been standardised by BIS. Mehra used brick aggregates as soft aggregates for the soil stabilization.

9. Which option represents the steps involved in mix design procedure of mechanical stabilization?
a) Gradation, proportioning and index property
c) Gradation, proportioning, stability and index property

Explanation: For the mix design procedure, there are four steps involved. The first one being gradation, then proportioning, carrying out tests for stability and index properties of the soil mix.

10. Aggregates with excess fines are difficult to compact.
a) True
b) False

Explanation: Aggregates having an excess amount of fines are coated with fines and hence it becomes easy to compact them. The mixes are more workable, which again contributes to easy compaction.

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