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Foundation and its types

Short answer

Foundation is the part below ground transferring superstructure loads safely to soil without shear failure or harmful settlement. Types include shallow: strip, isolated, combined, strap, raft, grillage; deep: pile, pier, well or caisson. Choice depends on soil bearing capacity, load, water table, settlement, and cost.

Define foundation. Describe types of foundation with necessary sketches.

Foundation is the part of a structure, usually below ground level, which transfers the loads of the superstructure to the soil safely without shear failure or harmful settlement.

Types of foundation

A. Shallow foundations (depth ≤\le width)

  1. Strip / wall footing: Continuous strip under walls.
  2. Isolated (spread) footing: Under a single column; flat, stepped or sloped.
  3. Combined footing: Carries two or more columns.
  4. Strap (cantilever) footing: Two footings joined with a strap beam.
  5. Raft (mat) foundation: A slab under the whole building for weak soil.
  6. Grillage footing: Steel beams in concrete layers.

B. Deep foundations

  1. Pile foundation: End-bearing or friction piles of timber, concrete or steel.
  2. Pier foundation: Large shaft of masonry or concrete.
  3. Well (caisson) foundation: Hollow sunk wells for bridges.
 Strip      Isolated     Raft         Pile
 |wall|      | col |   |c| |c| |c|   | col |
 [____]      [_____]   [__________]  [cap ]
                                      | | |

Choice depends on soil bearing capacity, load, water table, settlement, and cost. Shallow footing is used for firm soil; raft for low capacity; piles for deep firm layers.

✓ Answer checked by Claude Opus 5.5 (high effort)

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