Deep Foundations used in Construction
When it comes to constructing buildings and infrastructure in areas with challenging soil conditions, deep foundations are an essential part of the solution. Deep foundations provide stability and support for structures by transferring loads from the structure to deeper, more competent layers of soil or rock. In this blog post we will explore some types of deep foundations used in construction.
What are Deep Foundations?
Deep foundations are structural elements that are designed to penetrate the ground surface and transfer loads to deeper layers of soil or rock that have sufficient bearing capacity. Unlike shallow foundations, which rely on the upper layers of soil to provide support, deep foundations reach deeper into the ground to distribute the load and minimize settlement.
Types of Deep Foundations in Construction
The various types of deep foundations are used in construction, including pile foundations, cofferdam foundations, caissons foundations, basement foundations, and more.
1. Pile Foundation
A pile foundation is a type of deep foundation that is used to transfer the loads from a structure to deeper layers of soil or rock. It consists of long columns made of materials like concrete, steel, or timber that are driven into the ground. Pile foundations are commonly used in areas with weak or unstable soil conditions.
2. Cofferdam Foundation
A cofferdam foundation is a watertight enclosure that is constructed to allow construction work to be carried out in areas that are normally submerged in water. It is typically used for the construction of bridges, dams, and other structures in rivers, lakes, or coastal areas. The cofferdam is built by driving sheet piles into the ground and then pumping out the water from inside the enclosure.
3. Caissons Foundation
A caisson foundation is a watertight structure that is sunk into the ground to provide a stable foundation for structures like bridges, piers, and offshore platforms. It is typically constructed in dry conditions and then floated to the desired location where it is sunk into place. Caissons can be made of reinforced concrete, steel, or timber.
4. Basement Foundation
A basement foundation is a type of deep foundation that is used to create additional living or storage space below the ground level of a building. It is commonly used in areas where land is scarce or where the water table is high. Basement foundations can be constructed using various techniques such as concrete walls, pilings, or retaining walls.
5. Buoyancy Rafts (Hollow Box Foundations)
Buoyancy rafts, also known as hollow box foundations, are a type of deep foundation that is used in areas with high water tables or weak soil conditions. They are constructed by excavating a large area and then filling it with lightweight materials such as expanded polystyrene (EPS) or cellular concrete. The buoyancy rafts help to distribute the weight of the structure over a larger area, reducing the risk of settlement or failure.
Cylinders are deep foundation elements that are used to support structures like bridges, buildings, and towers. They are constructed by drilling a hole into the ground and then placing a cylindrical casing into the hole. The space between the casing and the surrounding soil is then filled with concrete or grout. Cylinders provide a strong and stable foundation for structures in areas with difficult soil conditions.
7. Drilled Shaft Foundations
Drilled shaft foundations, also known as drilled piers or drilled caissons, are deep foundation elements that are constructed by drilling a hole into the ground and then filling it with concrete or grout. They are commonly used to support structures like bridges, buildings, and towers in areas with difficult soil conditions or high load requirements. Drilled shaft foundations provide a high level of load-bearing capacity and can be used in a wide range of soil conditions.
Advantages of Deep Foundations
Deep foundations offer several advantages over shallow foundations in certain soil conditions:-
1. Increased load-bearing capacity
Deep foundations can distribute the load of the structure over a larger area, reducing the stress on the soil and minimizing settlement.
2. Ability to reach deeper, more competent soil layers
Deep foundations can penetrate through weak or unstable soil layers to reach stronger, more stable layers that can support the structure.
3. Resistance to lateral loads
Deep foundations provide greater resistance to lateral loads, such as wind or seismic forces, due to their deeper embedment and larger surface area.
4. Flexibility in design
Deep foundations can be designed to accommodate a wide range of soil conditions and structural requirements, making them suitable for various types of projects.
Deep foundations play a crucial role in ensuring the stability and safety of structures in challenging soil conditions. Whether it’s a high-rise building, a bridge, or an offshore platform, deep foundations provide the necessary support and load transfer to prevent settlement and structural failure. By understanding the different types of deep foundations and their advantages, engineers, and contractors can make informed decisions when it comes to selecting the most appropriate foundation system for their projects.
More Important Topics
FAQs on Deep Foundations used in Construction
What are Deep Foundations?
Deep foundations are structural elements that are used to transfer loads from a building or structure to the underlying soil or rock. They are typically used when the soil near the surface is unable to support the loads imposed by the structure.
Why are Deep Foundations used?
Deep foundations are used in construction for several reasons:
- When the soil near the surface is not strong enough to support the loads imposed by the structure.
- When the structure needs to be supported at a greater depth to avoid settlement or movement.
- When the structure needs to be supported in areas with high water tables or loose soil.
What are the different types of Deep Foundations?
There are several types of deep foundations used in construction:
- Pile Foundations: These are long, slender columns that are driven into the ground to transfer the loads to a deeper, more competent layer of soil or rock.
- Drilled Shafts: These are deep, cylindrical excavations that are created by drilling into the ground and then filling them with concrete or other materials.
- Caissons: These are watertight structures that are sunk into the ground and then filled with concrete to create a foundation.
How are Deep Foundations constructed?
The construction of deep foundations involves several steps:
- Site Investigation: A thorough investigation of the site is conducted to determine the soil conditions and the depth at which the deep foundation needs to be installed.
- Design: The deep foundation is designed based on the site investigation and the loads that need to be supported.
- Excavation: The excavation for the deep foundation is done using specialized equipment.
- Installation: The deep foundation is installed by driving piles into the ground, drilling shafts, or sinking caissons.
- Testing: The deep foundation is tested to ensure that it is able to support the loads imposed by the structure.
What are the advantages of Deep Foundations?
Deep foundations offer several advantages:
- They allow structures to be built on sites with weak or unstable soil.
- They can be used to support heavy loads.
- They can be designed to withstand lateral loads, such as wind or earthquakes.
Are there any disadvantages of Deep Foundations?
While deep foundations offer many advantages, they also have some disadvantages:
- They can be more expensive to construct compared to shallow foundations.
- They require specialized equipment and expertise.
- They can be time-consuming to construct.