End bearing piles, which are also known as point-bearing piles, are used to transfer superstructure load through low bearing capacity soil to a strong stratum such as rock or very dense sand and gravel. They infer most of their load-carrying capacity from the resistance of the strong soil layer at the end of the pile.
The end of the pile needs to be penetrated into the firm strata by at least three times the diameter of the pile. This measure is considered to achieve the full benefit of the ultimate strength of the firm layer under the pile tip. Prefabricated piles and auger type pile can be used as end-bearing piles.
The end bearing piles pass through weak soil and rest on strong soil layer, hence behaving like a column. That is why this type of pile is designed similarly to a reinforced concrete column. Buckling failure is not considered in the design of end bearing pile unless parts of it go through water or air.
Need for End Bearing Pile?
The firm strata under weak soil layer should be reachable otherwise friction pile is recommended.
End bearing pile minimizes settlement greatly, so it is a good choice for buildings in which settlement is critical
When a building has considerably heavy concentrated loads.
Large fluctuations in the sub-soil water level.
Canal or deep drainage lines exist near the foundations.
If the raft foundation is either costly or their adoption is impossible because of local difficulties.
Fig. 1: End Bearing Pile
Applications
High-rise structures
Bridges structures
Water tanks.
Fig. 2: Pile Foundation
Advantages
It experiences low settlement compared with other types of the pile like a floating pile. That is why multi-story buildings are mostly constructed on this type of pile.
The end bearing piles are generally used in most of the construction sites.
End bearing pile can be precast to specifications.
They can be prefabricated into any length, shape, and size and used on-site, hence reducing the completion time.
The end bearing pile goes does not experience buckling failure in weak soil except if it passes through air or water.
The pile rests on a firm stratum that could be stronger than the steel for the maximum design load that can be applied.
The cost of pile construction can be optimized since its length can be specified based on the depth of the firm soil layer.
The length of the pile to be used can be easily computed based on bedrock depth obtained from soil exploration borehole records.
Disadvantages
Heavy equipment is needed for the construction of end bearing.
The soil surrounding the pile may adhere to the surface of the pile and causes “Negative Skin Friction” on the pile.
Penulis
