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Define foundation; design criteria

Short answer

A foundation is the lowest part of a structure that safely transmits loads to the ground. Major criteria: depth below frost and weak soil, safety against shear failure with proper factor of safety, total and differential settlement within limits, structural strength, durability and economy. Two key considerations are bearing capacity and settlement.

Define foundation. Enlist the major criteria to be satisfied in the design of foundation. Mention two important things considered during foundation design.

Definition

A foundation is the lowest part of a structure, in direct contact with the ground, that transmits the load of the superstructure (and its own weight) safely to the soil or rock below.

Major design criteria

  • The foundation depth must be adequate (below frost, scour, weak soil and swelling soil).
  • It must be safe against shear failure (bearing capacity with a proper factor of safety).
  • Total and differential settlement must stay within permissible limits.
  • It must be structurally strong, durable and economical.

Two important things considered

  1. Bearing capacity: the soil must not fail in shear under the foundation pressure.
  2. Settlement: the soil must not settle more than the tolerable total and differential limits. For example, for isolated footings IS 1904 permits about 50 mm in sand and hard clay and about 75 mm in plastic clay.

✓ Answer checked by Claude Sonnet 5.5

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