End bearing piles, also known as point-bearing piles, are utilized to transfer the load of a superstructure from low bearing capacity soil to a robust stratum, such as rock or dense sand and gravel. The primary source of load-carrying capacity for these piles is the resistance provided by the strong soil layer at the end of the pile. To obtain the full benefit of the ultimate strength of the firm layer under the pile tip, the end of the pile must be driven into the firm strata by at least three times the diameter of the pile. Prefabricated piles and auger type piles can both be used as end-bearing piles.
Because end-bearing piles pass through weak soil and rest on a strong soil layer, they behave like a column. Therefore, this type of pile is designed in a similar manner to a reinforced concrete column. The design of end-bearing piles does not take into account the possibility of buckling failure, unless the pile passes through water or air.
Need for End Bearing Pile?
When dealing with weak soil layers, it is important to ensure that the strata beneath can be accessed. If this is not possible, it is recommended to use friction pile instead. This is because the weak soil layer can affect the strength of the pile, potentially leading to instability and damage to the building.
For buildings where settlement is a critical factor, end bearing pile is an ideal choice. This type of pile significantly minimizes settlement, which is especially important for structures with heavy concentrated loads. It is also suitable for buildings where sub-soil water levels fluctuate greatly, or where there are canal or deep drainage lines near the foundation.
In situations where raft foundation is either too expensive or not possible due to local difficulties, end bearing pile can be a good alternative. This type of foundation provides the necessary support and stability for the building, even in challenging soil conditions.
Applications
The three types of structures mentioned are high-rise buildings, bridges, and water tanks.
High-rise buildings are tall structures that typically have multiple floors and are used for various purposes such as residential, commercial, or industrial. They are often made of reinforced concrete or steel to ensure stability and safety.
Bridges are structures designed to span physical obstacles such as rivers, valleys, or roads. They are usually made of steel, concrete, or a combination of both and are built to withstand heavy loads such as vehicles and pedestrians.
Water tanks are structures used for storing water, typically for domestic or industrial use. They come in different shapes and sizes and can be made of various materials such as concrete, steel, or plastic. Water tanks must be designed to withstand the weight of the water they hold and other external factors such as wind and seismic activity.
Advantages
End bearing piles are a type of pile used in construction that experience low settlement when compared to other pile types like floating piles. This is why they are commonly used in the construction of multi-story buildings. They can be precast to specific specifications and are generally used in most construction sites.
One of the advantages of end bearing piles is that they can be prefabricated into any length, shape, and size and used on-site, which reduces completion time. Additionally, end bearing piles do not experience buckling failure in weak soil, except if they pass through air or water.
Furthermore, end bearing piles rest on firm stratum that can be stronger than steel for the maximum design load that can be applied. This means that the cost of pile construction can be optimized since the length of the pile can be specified based on the depth of the firm soil layer.
Finally, the length of the pile to be used can be easily computed based on the bedrock depth obtained from soil exploration borehole records. All of these advantages make end bearing piles a popular choice for construction projects.
Disadvantages
In order to construct an end bearing, heavy equipment is required. During the construction process, the soil that surrounds the pile may stick to its surface. This can create a phenomenon known as “Negative Skin Friction,” where the soil’s adhesive force causes a resistance against the pile’s movement. This can result in additional stress on the pile, which can ultimately affect its structural integrity. As such, it’s important to consider the potential impact of negative skin friction on the pile during the construction process.