Question

Assertion (A): Rankine's earth pressure theory should not be used for concrete retaining walls and Coulomb's theory should not be used for estimating passive earth pressures
Reason (R): Rankine assumed that the retaining wall has a vertical back and Coulomb assumed that the resultant reaction due to earth pressure acts at one-third the height of the wall.

• 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 B both A and R are true but R is not a correct explanation of A

The Rankine's theory assumes that there is no wall friction, the ground and failure surfaces are straight planes, and that the resultant force acts parallel to the backfill slope
For higher values of $\delta ,$ the error becomes unacceptable because of pronounced curvature of slip surface.