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TYPE OF FOUNDATIONS FOR ENGINEERING STRUCTURES.


For every super structure, there must be an underlying substructure. This substructure is also known as foundation. The essence of the substructure is to transmit the load of the superstructure to the ground and make it firm.

There are broadly two (2) types of foundations:

  1. Shallow Foundations
  2. Deep Foundations

Shallow foundation is any foundation that is between 1m to 3m. it is very near to the surface.

Deep foundation is any foundation that is beyond 3m.

The type of the foundation to be chosen is dependent on the type of superstructure to be erected and the load bearing capability of the soil in that place. These factors have to be determined by a competent Engineering Geologist.

Shallow foundation includes:

Strap footings. This is also called Cantilever footings. Here, two single footings are connected with a beam.

  1. Mat footings. Are mostly used in cases where the soil is so weak and the building loads extensive. A mat is a flat concrete slab massively reinforced with steel. The load is evenly distributed over the entire area. However, for heavy buildings, supplementary foundations can be erected to complement in the even distribution of loads.

Pad footing. Can either be Isolated footing (if it is only one footing); or Combined footing (if it supports two columns).

Pad footing is usually rectangular or square in shape.


Deep Foundations:
They include (but not limited to):
  1. Pile Foundation
  2. Caisson foundation.
The commonest is Pile Foundation and it what we will be discussing here.
It is used:
  1. When the bedrock is far from the surface and the soil is soft.
  2. When building bridges along rivers and/ or seas.
  3. If pad foundation is expensive.

Piles vary based on their composition and this in turn determines its strength and durability. They range from Timber piles, Pre-cast piles, Concrete piles, and Steel piles. Each has its own pros and cons.

Nevertheless, it is always advisable to consult a competent Engineering Geologist.

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