What Is Meant By Deep Foundation?
What Is Meant By Deep Foundation?
A deep foundation is a type of foundation which transfers loads from the surface to deeper layers in the ground.
These foundations usually have much greater depths than regular shallow foundations, and are constructed by driving piles into the ground and then either connecting them together with caps or arranging them as individual elements.
Deep foundations are used when soil has insufficient bearing capacity for a given structure, or when there is significant risk of differential settlement if using a shallow foundation.
The depth at which these deep foundations must be driven into the ground depends on various soil properties such as bearing capacity, moisture content, compressibility and dilatancy.
What Are Types Of Deep Foundation?
Welcome to our blog post about the different types of deep foundations used in civil engineering construction projects. In this article, we will cover the introduction and then delve deeper into basements, buoyancy rafts, caissons, shaft foundations and pile foundations.
The purpose of using deep foundations is to provide a strong foundation for buildings, bridges and other structures.
We will explain what each type of foundation consists of and discuss their advantages and disadvantages so that you can get a better idea of which one is suitable for a particular project. With this in mind, let’s dive right into the world of deep foundations!
Basements are often used as a form of deep foundation. Basements can provide much-needed additional space for homes, businesses and other buildings.
By extending the structure below ground level, it can serve as an anchor for the structure above.
Basements can be waterproofed or treated to make them better able to stand up to weathering and other environmental factors.
For large structures, basements offer an ideal way to provide extra load bearing strength and stability while also creating additional living spaces beneath the building.
- Buoyancy Rafts
Buoyancy rafts are deep foundation systems that make use of pontoons filled with air or other lightweight material to provide additional buoyancy and stability.
They are used to construct buildings close to water, or in areas where the soil is too soft for traditional deep foundations.
This type of foundation provides extra support by increasing the weight-bearing capacity of a structure’s base and can help spread the load evenly across several different points on the ground.
By using buoyancy rafts, deep foundation costs can be minimized and construction time can be reduced.
Caissons, also known as piers, are deep foundations designed to support very heavy structures. They’re used in situations where soil conditions are unfavorable and the loads imposed on the structure are particularly large.
Caissons consist of a steel or reinforced concrete shell that is sunk into the ground and filled with either concrete or stone.
The caisson is sunk until it reaches a suitable bearing stratum and then pressurized to enable it to embed itself into the ground further.
A significant advantage of using caisson foundations is that they can be installed underwater as well as on dry land.
- Shaft Foundations
Shaft foundations are deep foundations that involve excavating a hole and filling it with concrete or other material to form a shaft.
These types of foundation are typically used for taller buildings, bridges, heavy equipment, and other structures where extra support is necessary for stability.
Shaft foundations can be drilled into the ground, excavated from the surface, or driven down from above.
These foundations provide excellent bearing capacity and flexibility which makes them suitable for use in locations where soil conditions may vary over time.
- Pile Foundations
Pile foundations are a type of deep foundation which is used to transfer the load from a structure to a deeper and firmer layer of soil.
They are used in situations where the shallow soils are not able to bear the imposed loads or when there is a need for a pile-supported foundation system.
Piles can be made from reinforced concrete, steel or timber and then driven into the ground with impact hammers.
Driven piles have lower bearing capacity than drilled shafts but they are usually cheaper because they require less time and labour to install.
The amount of load transmitted by driven piles is determined firstly by driving force, secondly by type of soil, thirdly by its length and fourthly by its area.
Why Use A Deep Foundation?
A deep foundation is used where soils have high bearing capacity and where there is a need to anchor the structure in place.
It can be used for tall structures, large high rise buildings, or structures that require substantial soil stability and load-bearing capacity.
Deep foundations are also used when it is desirable to spread loads over a larger area to reduce settlement or vibration.
They are advantageous when there are obstructions such as rock outcroppings and timber piles, as they can be used to bypass these obstacles with minimal disturbance.
Furthermore, deep foundations can also be implemented in difficult ground conditions such as soft soils and scour areas thus making them a much more reliable choice than shallow foundation designs.
What Are The Disadvantages Of Deep Foundation?
Deep foundations have certain disadvantages, such as being expensive to construct, requiring specialized equipment and skilled labor, increased risk of loss of foundation strength due to soil-structure interaction and the potential for failure during construction, requiring significant technical knowledge to design and analyze, and having limited load transfer capacity when compared to shallow foundations.
Additionally, deep foundations may be difficult or impossible to install in certain soils such as those with high water content or if there are large boulders present.
Depending on the type of foundation chosen, there can also be an increase in environmental impact due to excavation and/or vibration from pile installation.
Finally, deep foundations usually require frequent maintenance due to their increased susceptibility to settlement and corrosion.
Why Are Deep Foundations More Expensive?
Deep foundations are more expensive than shallow foundations as they require more labor and materials to construct, such as drill bits, pumps, excavators, and casing pipes.
Deep foundations typically reach below the frost line and hence need to penetrate much further into the ground than shallow foundations. Additionally, they must sustain large loads from columns or walls up above.
This often necessitates additional reinforcement, such as steel bars or engineering calculations in order to ensure their stability.
Moreover, deep foundations often use complex technical processes that require specialized equipment and expertise, thus making them even more expensive.