A fully compensated raft foundation for a building is
- ADesigned as a very rigid raft
- BDesigned as a completely flexible raft
- CSuch that the weight of the excavated soil is equal to the load due to the buildingCorrect
- DSupported by piles of short length
Solution
Concept
Fully compensated (floating) raft
Formula
Net pressure = Building load/area − γ × Df = 0 (fully compensated)
Step-by-step solution
1. A fully compensated raft is excavated to such a depth that the weight of soil removed equals the weight of the building. 2. The net additional pressure on the soil is then zero.
Explanation
In a floating or fully compensated raft the pressure that the building imposes on the soil is balanced by the pressure relieved by the excavation. So the weight of the excavated soil equals the load of the building, and settlement is minimal.
Shortcut
Compensated = excavated soil weight = building weight.
Common mistake
Thinking compensation refers to raft stiffness.
Correct answer: C) Such that the weight of the excavated soil is equal to the load due to the building