Types Of Foundation

Foundation is the lowest part of a structure which provides a base for the super structure proper. This term includes the portion of the structure below the ground level as well as the artificial arrangement of concrete block, piles, raft, grillage, etc. provided to transmit the loads on the structure including the dead weight of the structure itself to the soil below.

If a steel girder provided in a structure is found to be weak and flexible, it can usually be strengthened by suitable means; if a column acting as a load bearing member in a building is found to be indequate, it can be made safe by providing additional reinforcement or by introducing intermediate columns, but if the foundation of a building yields and ruptures the structure, then little can be done to improve the situation.

Types of Foundation

Foundation can be broadly classified into two types

1. Deep Foundations
2. Shallow Foundations

Deep Foundations

In case, the strata of good bearing capacity is not available near the ground, the foundation of the structure has to be taken deep with a purpose of attaining a bearing stratum which is suitable in all respects. In addition there may be many other conditions which may require deep foundations for ensuring stability and durability of a structure. The most common forms of construction pertaining to deep foundations are:

• Piles
• Cofferdams
• Caissons

 

Shallow Foundations

When the foundation is placed immediately beneath the lowest part of the super structure, it is termed as shallow foundation. The object of this type of foundation is to distribute the structural loads over a wide horizontal area at shallow depth below the ground level. The various types of foundations which can be included under shallow foundation are:

• Spread Footings
• Grillage Foundation
• Eccentrically loaded Footings
• Combined Footings
• Raft Foundation

Causes of Failure of Foundation

• Unequal settlement of the sub - soil.
• Unequal settlement of the masonry.
• Horizontal movement of the soil adjoining the structure.
• shrinkage due to withdrawal of moisture from the soil below the foundation.
• Lateral pressure tending to over - turn the structure.
• Action of atmosphere.
• Lateral escape of the soil below the foundation.

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