Foundations

Load-settlement behaviour
Types of foundation
Bearing capacity
Settlement
Foundation design
Ground improvement
The foundation of a structure is in direct contact with the ground and transmits the load of the structure to the ground. Foundations may be characterised as shallow (pad, strip or raft) or deep (piles, piers or caissons). When designing foundations, two principal criteria must be satisfied:
Bearing capacityThere must be an adequate factor of safety against collapse (plastic yielding in the soil and catastrophic settlement or rotation of the structure).
SettlementSettlements at working loads must not cause damage, nor adversely affect the serviceability of the structure.
There are other considerations that may be relevant to specific soils, foundation types and surface conditions.
(Source By: Books & net)




1. Foundation design
Design is an iterative process. Designers use their experience to estimate the dimensions, then check whether the design is safe. If it is not safe, or the check indicated that it may be possible to make economies, then they modify the dimensions and repeat the calculations. For example:
Use presumed bearing values to obtain a first estimate of the size.
Calculate the ultimate bearing capacity (qf) at which collapse will occur.
Obtain the allowable bearing pressure from
Divide the design load by this allowable pressure to obtain a required area.
Select appropriate dimensions.
Calculate the likely settlement for this size of foundation.
Check that the predicted settlement due to this allowable bearing pressure is likely to be acceptable.

(Source By: Books & net)