The real success of a building’s strength is based on its foundation. When constructing on unstable soil conditions, deep foundations are necessary to ensure the building’s integrity and strength. Pile foundations achieve this by inserting piles underground to support the building’s loads and transfer it to the soil in deeper layers. Among various pile foundation types, end-bearing piles stand out as an effective solution for providing strength in weak soil layers.
Let’s examine the system, workings, and applications of end-bearing piles in detail.
What is an End Bearing Pile?
End-bearing pile is a type of structural element that provides strong foundational support for buildings, ensuring they remain stable. Typically made of concrete, timber, or steel, it comprises three parts: shaft, tip, and base. It is then inserted deep into the soil, connecting weak and strong layers (rock stratum, sand, or gravel). Its primary role is to transfer loads from the building structure to the rock stratum, enabling structures to withstand high loads.
How End Bearing Piles Work
End-bearing piles operate on the principle of transferring heavy loads to a stable, hard soil layer beneath unstable soil. To establish end-bearing pile foundations, rotary drilling or augers are employed to drill holes that reach the hard stratum. The size and diameter of the hole depend on the length of the piles.
After drilling, end-bearing piles are inserted through the soft layer, extending to the hard layer. The pile tip must reach and sit firmly on the rock layer or dense sand. Thereafter, the heavy load of the building structure can be transferred to the piles, with the pile tip withstanding loads due to the resistance offered by the rock or gravel.
Site preparations and safety arrangements are carried out under the supervision of experienced engineers to ensure proper installation.
What are End Bearing Piles Made of?
End-bearing piles are usually made from three primary materials: wood, steel, and concrete.
Timber Piles
The size and length of the piles vary depending on the tree species. These piles are made from pine, sal, fir, or teak woods. They are treated with coatings and preservatives to prevent decay and pest damage. But placing the timber pile below the groundwater level can protect the timber against rot and decay. Furthermore, to protect the tip’s surface from soil adhesion, it can be covered with a toe cover. Timber piles are suitable for small building structures in weak soil conditions.
Steel Piles
They are manufactured from fabricated steel sections and treated with protective coatings. They possess high strength and long-lasting durability. These steel piles can withstand heavy loads, making them the best option for heavy structures. Notably, H-piles, a type of steel pile, can endure heavy stresses. They are designed to transfer heavy loads to regions with solid rock or dense sand.
Concrete Piles
Concrete piles are versatile, as they combine the strength of concrete with steel reinforcement. They provide reliable support and corrosion resistance in corrosive soil regions. These piles are generally pre-manufactured and transported to construction sites. Concrete piles are often ideal for heavy structures and marine projects. They are usually installed above the ground water level in weak soils.
What are the Common End Bearing Pile Sizes?
Size of end bearing piles vary depending on the soil conditions, structure of the building and materials used.
Timber Pile
Short piles (less than 14 metres): Minimum tip diameter = 150 mm
Long piles (more than 18 metres): Minimum tip diameter = 125 mm
Concrete Pile
Typical concrete pile shapes include square, triangle, circle, and octagon. They are manufactured in lengths from 3 to 13 metres.
Steel Pile
Steel Pile Dimensions for End-Bearing
– Diameter Range: 250-600 mm
– Minimum Thickness of gauge: 20 mm
– Shape Options: I-shaped, Hollow, H
Applications of End Bearing Piles
End bearing piles have a wide range of applications due to their ability to provide stability, strength, and longevity. Some of these applications are:
High-Rise Structures
In urban landscapes, tall buildings require strong deep foundations rather than wide surface footings. To withstand heavy loads, deep foundations are crucial, especially in weak top soil conditions. End bearing piles transfer loads and stresses to underlying rock layers, supporting the building’s strength, providing structural integrity and ensuring safety.
Bridge Structures
For bridges, every element, such as piers and beams, relies on strong foundational support. End bearing piles emerge as a solution due to their high load-bearing capacity. Additionally, they are ideal for bridge construction in marine areas, resisting water stresses and preventing corrosion.
Water Tanks
End bearing piles resist water pressure and soil settlement, providing a strong base for water tanks. Their wide and long dimensions require robust foundational support, which end bearing piles effectively provide, accommodating massive loads and preventing damage and leakage.
Advantages of End bearing Piles
End bearing piles offer several benefits, making them a popular choice for deep foundation projects.
- Reduced Settlement: End bearing piles settle less due to their deep foundation in solid ground.
- Suitable for Tall Structures: Ideal for high-rise buildings as end bearing piles transfer heavy loads to solid rock, ensuring structural integrity.
- No Buckling Issues: Their deep installation prevents buckling, providing added stability and safety.
- Customisability: End bearing piles can be pre-manufactured to specific sizes and shapes.
- Stability in Weak Soils: End bearing piles provide strong stability in areas with poor soil conditions.
- High Load Capacity: End bearing piles can handle massive weights without compromising foundation stability.
Disadvantages of End bearing Piles
While end bearing piles offer several benefits, they also have some drawbacks:
- High Installation Costs: Heavy equipment and specialised drilling vehicles are required, increasing installation expenses.
- Soil Friction and Adhesion: Friction around the pile can cause soil to stick, potentially reducing load bearing capacity. However, covering the pile tip can mitigate this issue.
- Depth-Dependent: End bearing piles require reaching solid rock or firm ground, which can be challenging to find and costly in areas with deep or unpredictable soil conditions.
- Environmental and Noise Concerns: Drilling and installation can generate excess noise and vibrations, which can disrupt nearby ecosystems, such as residential areas, wildlife habitats, and underground utilities, causing disturbance to both human and animal life.
Conclusion
End-bearing piles are one of the most effective deep foundation types. They are capable of resisting lateral, vertical, and uplift loads. They serve as a crucial structural component, providing immense strength and stability to buildings, especially high-rise ones. Moreover, their specialised techniques ensure longevity. By employing proper techniques and selecting suitable materials for piles, builders can fully benefit from their use in building structures.
FAQs
Piles made from concrete, steel, and timber can be used for deep foundations. It is chosen based on project needs and soil conditions.
End-bearing piles use drilling, driving, or augering techniques for installation and it depends on soil conditions and pile material.
Regular checks and monitoring for damage or settlement is crucial to ensure long-term performance.