The distinction between shallow and deep foundations
Shallow and deep foundations represent the degree of soil depth. It is a shallow foundation if the depth of a foundation is less than the width of the footing and it is less than 10 feet deep. Shallow foundations are used when the existing surface soil can support the imposed loads.
If the depth of a foundation is greater than the width of the building’s foundation, it is a deep foundation. Deep foundations are frequently used to carry construction loads deep into the ground.
Just a fact: the Burj Khalifa in Dubai, the world’s tallest structure of more than 800 meters high, required 45K cubic meters of concrete and 192 piles each 50m deep.
Reasons for deep foundations
There are certain situations when a deep foundation is preferable:
- Surrounding soil has somewhat weak bearing capacities – 700 pounds per square foot and less.
- Expansive clays near the surface.
- Soil is susceptible to being carried away by erosion or scour
Categories of deep foundations
The three types of deep foundations are pile, well, and caisson foundations.Pile foundations
A pile foundation is a set of columns installed in the ground and constructed to transfer loads to the earth’s subsurface. A pile is a long cylinder composed of durable material, such as concrete. They are placed in the ground to provide a firm foundation for structures that are erected on top of them. Piles transfer the loads from buildings to hard strata, rocks, or soil with high bearing capacity. They keep a building stable and are more resistant to erosion and scour.
Piles are driven into the ground using a pile driver, a device that drives the pile into the ground while maintaining it at a vertical angle. The procedure is simple: lifting a weight and dropping it onto the top of the pile repeated many times.
Piles should be hammered into the ground until they are firmly embedded and cannot be driven further in. This method is a superior choice because it minimizes soil displacement around the pile and results in the greatest bearing capacity for each pile.
Every pile has a zone of influence on the soil surrounding it, therefore piles must be spaced sufficiently apart to ensure that the loads are equally dispersed.
Depending on their function, the pile types are the following:
- bearing piles:
Bearing pile driving continues until a solid layer of soil is reached. The piles rest on hard strata and serve as pillars for the structure. They transfer the building load to the underlying hard stratum.
- friction piles:
Friction piles are employed when the soil is soft and hard strata is not accessible. These piles are long and have rough surfaces to enhance surface area and frictional resistance.
- friction-cum-bearing piles:
Piles are set at an angle and are frequently used to enforce slopes.
- batter piles:
Batter piles are inclined to resist slanted forces.
- guide piles:
These piles are used in cofferdams to provide a solid footing for underwater development.
- sheet piles:
Sheet piling is a form of excavation support and soil retention. It forms a barrier that keeps the soil away from the building.
Depending on the material used, there are:
- timber piles,
- concrete piles,
- sand piles,
- steel piles.
Our team of G8 Builds contractors has extensive expertise in developing innovative pile solutions in different industries. We have considerable expertise in this area and would be delighted to provide you with advice and a free quotation.