Question

Assertion (A): The possibility of piping failure in earth dams is more if black cotton soil is the foundation material.
Reason (R): The highly expansive black cotton soils are the most common soils wherever basalt rock is present.

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:
Codes:

• 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 D A is false but R is true

(d)
Black cotton soils are held together even at critical hydraulic gradient due to inherent cohesion that holds the grains together. Possibility of piping failure is less because the cohesion component of shear strength is an independent quantity.