The contact pressure distribution under a rigid footing on a cohesionless soil would be
- AUniform throughout
- BZero at centre and maximum at edges
- CZero at edges and maximum at centreCorrect
- DMaximum at edges and minimum at centre
Solution
Concept
Contact pressure under a rigid footing
Step-by-step solution
1. On clay a rigid footing has maximum contact pressure at the edges and minimum at the centre. 2. On cohesionless soil (sand) it is zero at the edges and maximum at the centre.
Explanation
In sand, the soil near the edges has little confinement, so it cannot carry load, and the pressure at the edges is nearly zero. The distribution is parabolic with the maximum at the centre.
Shortcut
Clay = edges high. Sand = centre high.
Common mistake
Reversing sand and clay.
Correct answer: C) Zero at edges and maximum at centre