Understandings about Pile Foundation
Pile foundation is a type of deep foundation system used to support heavy load or to transfer loads from a structure to a deeper and more stable layer of soil or rock below the ground surface. Pile foundations are commonly used in situations where shallow foundations, such as spread footings or mat foundations, are inadequate due to weak or compressible soil conditions.
The study of foundation is the sturdy of base of a building or any structure, similar to how the roots support a tree. It is the part of a structure that rests directly on the ground and is responsible for holding up the entire structure. Foundations ensure that buildings are stable, safe, and can withstand the forces of nature like wind, earthquakes, and the weight of structure itself, people, and things inside them.
Pile Foundation- Types and Functions of Pile Foundation
Pile foundation is a type of deep foundation used in civil engineering and construction field to support structures when the soil near the surface is not strong enough to bear the loads imposed by the building or other structure. Deep foundations are crucial for ensuring the stability and safety of various structures like buildings, bridges, and offshore platforms.
What is Pile Foundation? Detailed Explanation
Pile foundation is a type of deep foundation which consist of long, slender columns, often made of materials like concrete, steel, or timber (see in detail below). These columns, called piles, are driven or drilled deep into the ground until they reach a stable and load-bearing stratum, typically a layer of dense soil or even bedrock. The primary function of pile foundations is to transfer the heavy loads from the structure they support to a deeper and more stable layer of soil or rock below the ground surface, preventing excessive settlement and ensuring the structural integrity of the building.
Pile foundations are indispensable in situations where shallow foundations, like traditional spread footings, are not feasible due to weak or unstable surface soils. They are particularly useful in areas with high water tables, where the stability of structures can be compromised. By extending deep into the ground, pile foundations provide a secure and reliable means of supporting structures and distributing their loads to ensure their longevity and safety.
What is Load-Bearing Mechanisms in Pile Foundations?
There are two fundamental load-bearing mechanism in pile foundation, they are end bearing and skin friction. End bearing occurs when the piles rest on a firm stratum at their base, and the load is directly transferred to this stable layer. Skin friction, on the other hand, relies on the frictional resistance between the surface of the piles and the surrounding soil to support the load. The choice between these mechanisms depends on factors such as soil conditions, foundation design, and the specific requirements of the project.
What is Deep Foundation?
Deep pile foundation is a type of foundation system used in civil engineering and construction to support structures when the soil near the surface is unable to bear the loads imposed by the building or when the structure requires additional stability. Deep pile foundations involve the installation of long, slender columns (referred to as "piles") into the ground to transfer structural loads to deeper, more stable layers of soil or bedrock. These foundations are employed when shallow foundations, such as spread footings, are insufficient due to weak or unstable surface soils.
What are the Types of Deep Foundation?
Types of deep foundation are "Pile Foundation" and "Caissons or Drilled Shaft". The choice of deep pile foundation depends on factors such as soil conditions, structural loads, access constraints, and project requirements. Each category offers specific advantages and is selected to ensure the foundation's stability and safety for the intended application.
Types and Functions of Pile Foundation
The driven piles, bored piles, micro piles, and screw piles are under the pile foundation.
1. Driven Piles
- Steel Piles: These are steel piles in the shape of an "H" or "O" from top, and they are driven into the ground. They are commonly used in a variety of soil conditions.
- Concrete Piles: These piles are made of reinforced concrete and are also driven into the ground. They are suitable for both compression and tension loads.
- Timber Piles: Timber piles are made of wood and are driven into the ground. They are often used in marine applications and in areas with corrosive soils.
2. Bored Piles (Drilled Piles)
- Auger-Cast Piles: These piles are created by drilling a hole into the ground with an auger and then filling it with concrete as the auger is removed. They are suitable for soft or loose soils.
- Continuous Flight Auger (CFA) Piles: CFA piles are formed by drilling with a continuous flight auger, and concrete is pumped through the hollow stem as the auger is withdrawn. They are commonly used in construction where low noise and vibration are required.
3. Micro-Piles
Micro-piles are small-diameter piles, often made of high-strength steel or threaded bars, that are drilled or driven into the ground. They are suitable for restricted access areas and can be used in tension and compression applications.
4. Screw Piles (Helical Piles)
Screw piles, or helical piles, have helical (spiral) blades on the shaft, which are twisted into the ground. They are effective in both tension and compression and are commonly used in foundation repair and temporary structures.
5. Caissons or Drilled Shafts
Caissons, also known as drilled shafts or drilled piers, are large-diameter cylindrical foundations created by drilling deep into the ground and filling the hole with concrete. They are commonly used in bridge and high-rise building construction.
Types of Pile Foundation Based on Effect of Soil
Pile foundations can be classified based on their behavior and the effect they have on the surrounding soil. The classification based on the effect of soil includes the following types:
1. End-Bearing Piles (Point-Bearing Piles)
These piles primarily rely on the bearing capacity of the soil or rock stratum at the bottom of the pile (the pile toe) to support the structural loads. The pile is driven or placed deep enough to reach this load-bearing layer. End-bearing piles are most effective when the underlying stratum is strong and can carry the loads imposed by the structure.
2. Friction Piles (Skin-Friction Piles)
Friction piles primarily rely on the frictional resistance between the surface of the pile and the surrounding soil to support the loads. These piles are driven or installed into soils that may not have a strong bearing capacity at depth. The surface area of the pile provides the necessary resistance to prevent settlement. Skin-friction piles are effective in cohesive (clayey) or granular (sandy) soils.
3. Combination Piles (Friction-End Bearing Piles)
Combination piles are designed to utilize both end-bearing and skin-friction mechanisms to support loads. They are used in situations where the soil conditions vary with depth. The upper portion of the pile relies on friction, while the lower portion rests on a load-bearing stratum. This combination allows for effective load transfer in variable soil profiles.
4. Floating Piles
Floating piles, also known as buoyant piles, are used in waterlogged or saturated soil conditions where the piles displace water as they are driven into the ground. These piles are primarily used to support structures in areas with a high water table, such as wetlands or coastal regions.
5. Tension Piles (Uplift Piles)
Tension piles are designed to resist uplift forces rather than vertical compression loads. They are often used to anchor structures that may experience uplift due to factors like wind or buoyancy. Tension piles are installed to provide the necessary resistance against upward movement.
6. Compaction Piles
Compaction piles are used to improve the load-bearing capacity of loose or compressible soils. They are not driven to the load-bearing stratum but are installed at intermediate depths to densify the surrounding soil and reduce settlement potential. These piles are often used in ground improvement projects.
7. Prestressed Piles
Prestressed piles are piles that are pre-tensioned or pre-compressed before installation. They are designed to counteract the effects of settlement, especially in situations where significant structural loads or differential settlement may occur.
Types of Pile Foundation Based on Material
Pile foundations can also be classified based on the material used for the piles. The classification based on material includes the following types:
1. Concrete Piles
These piles are made of reinforced or prestressed concrete and are widely used in various construction projects. Concrete piles can be precast or cast in place, and they are suitable for a wide range of soil conditions and load-bearing requirements.
2. Steel Piles
Steel piles are typically made of high-strength steel and are commonly used in situations where corrosion resistance is a concern or when piles need to be driven to significant depths. They are often used in marine applications and industrial settings.
3. Timber Piles
Timber piles are made of wood, typically hardwood or treated softwood, and are used in both marine and land-based construction projects. They are suitable for situations where environmental considerations or aesthetics are important.
4. Composite Piles
Composite piles are made by combining different materials to leverage the advantages of each. For example, a composite pile may consist of a steel core surrounded by a concrete shell. This approach allows for corrosion resistance while maintaining structural strength.
5. Fiberglass Reinforced Plastic (FRP) Piles
FRP piles are composed of fiberglass strands embedded in a polymer resin matrix. They are lightweight, corrosion-resistant, and suitable for use in corrosive soil or water environments.
6. Aluminum Piles
Aluminum piles are made of aluminum alloys and are chosen for their lightweight properties and resistance to corrosion. They are commonly used in marine and offshore applications.
7. Vinyl Piles
Vinyl piles are made of high-density polyvinyl chloride (PVC) and are used in marine environments. They are known for their durability, low maintenance, and resistance to marine borers and rot.
FAQs👉
What is Well Foundation?
Well foundation is a type of deep foundation used in civil engineering and construction, particularly in projects involving bridge construction in water bodies like rivers or estuaries. This foundation type is designed to support heavy structures, such as bridge piers or abutments, in areas with challenging or waterlogged soil conditions.
Selection of Type of Pile Foundation
The selection of the right foundation type for a construction project hinges on a multitude of factors. Engineers and architects meticulously consider the site's soil conditions, evaluating bearing capacity and composition, alongside structural loads to ensure the chosen foundation can adeptly distribute these forces.
Geological features, such as bedrock or groundwater presence, and hydrological aspects are also scrutinized, often necessitating tailored foundation solutions.
Environmental impact, construction timelines, and budget constraints play pivotal roles, as do accessibility and space limitations, which demand adaptable foundation choices.
Compliance with local building codes, responsiveness to environmental conditions like seismic activity, and alignment with architectural design and future expansion needs further contribute to this comprehensive decision-making process.
Hence, selecting the appropriate foundation type emerges as a critical determinant of a project's safety, stability, and success.
What is the Depth of Pile Foundation?
The depth of a pile foundation can vary widely depending on several factors, including the specific engineering requirements of the project, soil conditions at the construction site, and the type of piles being used. Typically, pile foundations are designed to extend deep enough into the ground to reach a stable and load-bearing stratum, which could be a layer of dense soil or even bedrock.
In some cases, pile foundations may only need to be a few meters deep, while in other situations, they may need to extend tens of meters or even deeper. The depth is determined through geotechnical investigations and engineering analysis, including soil testing, to ensure that the piles can effectively transfer the structural loads to the stable subsurface materials.
It is important to note that the depth of pile foundations is a critical design consideration to prevent settlement, ensure structural stability, and meet safety requirements for the specific project. Therefore, the depth is determined on a case-by-case basis, and it can vary significantly from one construction site to another.
What is the Process of Pile Foundation?
The process of constructing a pile foundation involves several steps, some of them are following:
Site Investigation: Before beginning pile foundation construction, a thorough site investigation is conducted to assess soil conditions and determine the appropriate type and length of piles required. This typically includes soil testing, geological surveys, and analysis of subsurface conditions.
Design: Based on the site investigation findings, structural engineers design the pile foundation. This includes selecting the type of piles (e.g., driven piles, drilled piles, or auger-cast piles), calculating the required pile length, and determining the load-bearing capacity.
Pile Installation: The actual construction of the pile foundation begins with the installation of the piles. The method used depends on the chosen pile type.
Load Testing: After pile installation, load tests may be conducted to verify the capacity and performance of the foundation. This involves applying controlled loads to the piles and monitoring their response to ensure they meet design specifications.
Foundation Cap Construction: Once the piles are installed and tested, a foundation cap or mat is constructed on top of the piles. This cap distributes the structural loads from the building to the individual piles and ensures stability. It is typically made of reinforced concrete.
Structural Construction: With the foundation in place, the construction of the superstructure (building or structure) can proceed. The load-bearing walls, columns, and other structural elements are erected on the foundation cap.
The specific process for a pile foundation can vary based on the project's requirements, site conditions, and engineering design. It is essential to follow industry best practices and safety guidelines throughout the construction process to ensure the foundation's integrity and the overall safety of the structure.
Terms and Definitions in Pile Foundation
What is a Pile?
Pile is a long, slender structural element made of materials like concrete, steel, or wood. It is driven, drilled, or vibrated deep into the ground to provide support for structures by transferring loads to stable soil or bedrock below the surface.
Explain Abutment Pile
An abutment pile is a type of foundation pile specifically used in the construction of bridge abutments. Bridge abutments are the supporting structures located at the ends of a bridge. Abutment piles are strategically placed near the abutment structure and are designed to withstand and transfer the lateral and vertical loads generated by the bridge and any adjacent soil or fill. These piles are crucial for stabilizing the bridge's ends, resisting horizontal forces, and transmitting vertical loads from the bridge deck to the underlying soil or bedrock. The design and installation of abutment piles are essential to ensure the stability and safety of the bridge's abutment structure.
Explain Pier Pile
A pier pile is a type of foundation pile used to support bridge piers. Bridge piers are vertical support structures positioned at intervals along the length of a bridge. They are responsible for carrying the weight of the bridge deck and distributing the associated loads to the foundation. Pier piles are strategically placed at locations where bridge piers will be constructed. These piles provide crucial vertical and lateral support for the piers, ensuring the structural integrity and stability of the entire bridge. The design and placement of pier piles are essential to ensure that the piers can safely bear the loads from the bridge deck and effectively transmit them to the foundation below.
Explain Pile Cap
A pile cap is a thick concrete mat or slab that rests on top of a group of piles. It serves to distribute the loads from the superstructure (such as a building or bridge) to the individual piles, providing a stable foundation.
Explain Test Pile
A test pile is a foundation pile that is installed and loaded to evaluate the bearing capacity and behavior of the soil and the suitability of a particular pile design for a construction project. Test piles help engineers make informed decisions about the design and capacity of the foundation.
Explain Seismic Block
A seismic block, also known as a seismic mass or a mass block, is a heavy concrete block placed on top of piles or columns in buildings or structures to increase stability and dampen the effects of seismic (earthquake) forces. It helps prevent excessive lateral movement during an earthquake.
Explain Pile Anchorage
Pile anchorage refers to the secure attachment or embedding of the upper portion of a pile into the structure it supports. This connection ensures that the pile can effectively transfer loads between the superstructure and the foundation.
Explain Lateral Design Load of Pile
The lateral design load of a pile is the horizontal or sideways force that the pile is designed to withstand. It typically arises from wind, seismic forces, or other lateral loads acting on a structure. Engineers calculate and design piles to resist these lateral forces safely.
Explain Vertical Design Load of Pile
The vertical design load of a pile is the downward force or load that the pile is designed to support. This load includes the weight of the superstructure, live loads (e.g., occupants, furniture), and any other vertical forces acting on the structure. Piles are designed to carry these loads without excessive settlement or deformation.
What is "Bulb" in Pile foundation?
In pile foundations, a "bulb" refers to a widened or enlarged section at the bottom of a foundation pile, usually resembling the shape of a bulb or an inverted cone. This bulbous enlargement is intentionally designed to enhance the load-bearing capacity and stability of the pile. It is commonly used in friction piles, where the primary mechanism of load transfer is the frictional resistance between the pile and the surrounding soil or rock. See below the functions of "bulb" in pile foundation-
Increased Frictional Resistance: By enlarging the base of the pile, the surface area in contact with the surrounding soil or rock is increased. This greater surface area enhances the frictional resistance, allowing the pile to support heavier vertical and lateral loads.
Stabilization: The bulb can help prevent the pile from sinking further into soft or loose soils, providing stability and preventing excessive settlement.
Enhanced Bearing Capacity: The presence of the bulb effectively increases the load-bearing capacity of the pile, making it capable of supporting the structural loads imposed by the superstructure it serves.
Declaimer: This post is written for educational purpose only and we do not suggest to use for professional purpose.
