Question

Directions: The following items consists of two statements; one labelled as ' Assertion (A)' and the other as 'Reason (R)'. You are to examine these two statements carefully and select the answers to these items using the codes given below:

Assertion (A): In a compaction test at ${\gamma }_{dmax}$ and OMC, the degree of saturation is never 100%.

Reason (R): It is not possible to expel all the air entrapped in soil by compaction.

• A. both A and R are true and R is the correct explanation of A
• B. both A and R are true but R is not a correct explanation of A
• C. A is true but R is false
• D. A is false but R is true

Answer 1

The correct option is A both A and R are true and R is the correct explanation of A

The water content corresponding to the maximum dry density is known as the optimum water content (O.W.C.) or the optimum moisture content (O.M.C.).
For a given water content, theoretical maximum density,
$(\rho d{)}_{theomax}$, is obtained corresponding to the condition when there are no air voids (i.e. degree of saturation is equal to 100%). The theoretical maximum dry density is also known as saturated dry density $({\rho }_d{)}_{sat}$ , In this condition, the soil becomes saturated by reduction in air voids to zero but with no change line water content. It may be mentioned that compaction methods cannot remove all the air voids, and, therefore, the soil never becomes fully saturated. Thus, the theoretical maximum density is only hypothetical. The line indicating the theoretical maximum density can be plotted along with the compaction curve. It is also known as zero air void line or 100% saturation line.