Foundation pressure distribution: For a perfectly rigid foundation base resting on a homogeneous elastic soil and subjected to a concentric vertical load, how does the contact pressure vary?

Difficulty: Easy

Correct Answer: Uniform over the base

Explanation:


Introduction / Context:
Contact-pressure assumptions depend on the relative rigidity of the footing and the soil. For a perfectly rigid footing on homogeneous soil under concentric vertical load, the conventional assumption is a uniform pressure distribution.


Given Data / Assumptions:

  • Rigid foundation base (no differential deformation).
  • Homogeneous supporting soil.
  • Concentric vertical loading (no overturning moment).


Concept / Approach:

Rigid base implies plane sections remain plane; with symmetry and no moments, the soil reaction is uniform to balance the applied load.


Step-by-Step Solution:

Apply equilibrium: resultant reaction = applied vertical load.With no net moment and rigidity, reaction intensity = constant = Load / Area.


Verification / Alternative check:

Flexible bases show non-uniform distributions (often more at center); presence of moments shifts maxima to edges. The stated ideal leads to uniform pressure.


Why Other Options Are Wrong:

Edges higher or center zero require eccentricity or flexibility; arbitrary shapes contradict concentric, rigid conditions.


Common Pitfalls:

Confusing rigid with flexible base assumptions; ignoring effect of eccentric loading and rocking.


Final Answer:

Uniform over the base

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