Which of the following is an assumption made in Rankine’s Earth Pressure Theory?
- AThe soil is anisotropic and partially saturated
- BThe wall has friction with the backfill
- CThe ground surface is planar and horizontalCorrect
- DThe backfill material is cohesive and heterogeneous
Solution
Concept
Assumptions in Rankine earth pressure theory
Formula
NONE
Step-by-step solution
1. Rankine's earth pressure theory uses simplified idealizations regarding soil behavior and backfill conditions. 2. Following the given key for this preliminary exam question, option A is selected as the correct answer. Answer: C
Explanation
Rankine earth pressure theory simplifies lateral earth pressure analysis by assuming a homogenous, dry, and cohesionless soil mass bounded by a horizontal planar ground surface. It also assumes the retaining wall back face is vertical and smooth, ignoring friction between the wall and soil. Therefore, option C correctly identifies an assumption made in Rankine theory.
Why the other options are wrong
B) Rankine's theory assumes a smooth retaining wall with zero wall friction. D) Rankine's theory assumes homogeneous, cohesionless backfill soil.
Shortcut
Rankine theory assumes a smooth vertical wall with a planar ground surface.
Common mistake
Selecting option B or D by confusing Rankine's theory with Coulomb's theory, which accounts for wall friction.
Correct answer: C) The ground surface is planar and horizontal