Construction of Deep Foundation

Foundation means the lowest segment of the building or structure that gets in touch with the soil to transmit loads from the structure to the soil securely. Normally, the foundation is categorized as shallow foundation and deep foundation.

The purpose of a shallow foundation is to transmit the load to a stratum that exists in a shallow depth. The function of deep foundation is to transmit the load to a profound depth underneath the ground surface.

Deep foundation should be used when it is required to expand the building vertically in future.

Deep foundation bears loads from a structure through feeble compressible soils or fills on to harder and less compressible soils or rocks at depth, or for functional purposes. Normally, deep foundations should be constructed at depths >3 m underneath finished ground level for their base bearing strength susceptible to surface conditions.

Deep Foundation is categorized as follow :-

1. Basement foundation: It belongs to the substructures to arrange working or storage space underneath ground level. The structural design is subject to their functional requirements other than from considerations of the most effective method of defending exterior earth and hydrostatic pressures. They are built in place in open excavations.

Also Read: Benefits of Pier and Beam Foundation

2. Buoyancy Rafts (Hollow Box Foundations): Buoyancy rafts stand for hollow substructures to arrange a buoyant or semi-buoyant substructure under which the net loading on the soil is minimized to required low intensity. Buoyancy rafts is created to be cast as caissons, they are built in place in open excavations.

3. Caissons Foundations: Caissons belong to hollow substructures which are built on or adjacent to the surface and then cast as a single unit to their desired level.

4. Cylinders: Cylinders stand for small single-cell caissons.

5. Drilled Shaft foundations: Shaft foundations are built inside deep excavations which are supported by lining built in place and later filled with concrete or other pre-fabricated load-bearing units.

6. Pile foundations: Pile foundations are comparatively long and slender members which are built by providing preformed units to the required founding level, or by driving or drilling-in tubes to the desired depth.

The tubes are filled with concrete prior to or during removal or by drilling unlined or entirely or partially lined boreholes to be filled with concrete later on.