Foundation in civil engineering has many functions depending on the nature of the structure. As it carries the entire structure, foundations are probably the most stressed. Knowing this nature, it is important to know the types of foundation so we’ll better grasp its uses and functions. The goal is to find the most economical foundation that wouldn’t compromise the quality.
Foundation systems may be breakdown into two; shallow foundation and deep foundation.
Shallow foundations are the foundation of depth on the average of six feet. It is generally used when the load carried isn’t that colossal and the natural ground has sufficient soil bearing capacity. This type of foundation is usually used in residential projects.
The foundations of all kinds of structure shall undergo checking of the structural engineer. He or she must also must design the the foundation before it can be constructed.
Shallow foundations can be further broken down into 5 subdivisions.
1. Isolated footing
Isolated footing is the most budget-friendly foundations of all. Generally square, but can be rectangular or circular. This is a foundation with a column on top.
2.Wall footing
Wall footing is a type of footing used in masonry works. It is a continuously cast strip along the length of the wall. It is reinforced with 8mm or 100mm rebar horizontal and vertical. In other countries such as the United Arab Emirates, the common reinforcement for block wall is wire mesh and hold fast.
3. Combined footing
The combined footing is the same with isolated footing except that it has 2 column or pillar on it. Foundation used for 2 columns of minimal distance.
4. Cantilever or Strap footings
Cantilever footing has properties same with combined footing except for footings under the column are cast separately but is joined by a beam. Beams are added to help promote strength on resisting settlement and shear or seismic movements.
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5. Mat Foundation
Mat foundations are foundation used for demanding structures where the loads for both column and walls are high. These are usually used on weak soil (where piles are not used) to prevent differential settlement of footings due to loads.
Deep foundations are used when soil strata near the natural ground line don’t have sufficient soil bearing capacity. It consists of piles or pier foundations at their bases. Deep foundation generally has spread footing supports. The pile at the base distributes the load of the structure by the friction (on the piles’ faces) and the actual load bearing at the tip.
Deep foundations are generally used for mega-structures like bridges, dams, high-rise buildings, airports, and piers. Deep foundations can be broken down into 2 subdivisions.
6. Pile foundation
Pile foundations are used for mega-structures. These are foundations where the load is transferred to a more stable soil stratum beneath the surface (hard rock). Due to the friction of the pile and the soil, this type of foundation also prevents uplift in effect of seismic movements or heavy wind loads.
7. Pier or Caisson Foundation
If pile foundation is for megastructures, pier foundations are for ultra-mega structures. The depth of this foundation can reach up to 100 meters. The properties are the same with the pile foundation except that these are cast in-situ. The construction of drilled shafts uses is done using an auger. Due to extremely deep hauling, these foundations are not suitable for clayey or water-bearing granular soils.
The design of foundations is depending on the size of the superstructure, the highest the structure the bigger the foundation.
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