Piling
Pile foundations work by inserting large amounts of wood, steel, or concrete into the soil to create a sturdy base for construction projects. Without a solid foundation, buildings would not be able to stand for long. Piling is a complex and skilled job that requires careful planning, measuring, and hard labor. It is crucial to ensure that the base is secure and the piling is done correctly to guarantee a solid structure. However, the piling process depends on various factors, including the condition of the soil. Wet soil, for instance, is not suitable for piling.
PILE FOUNDATIONS
Pile foundations play a crucial role in providing stable support to various structures. These foundations consist of long cylindrical structures made of durable materials like concrete, which are inserted into the ground. They are particularly useful in situations where the surface soil is weak or when structures have heavy and concentrated loads.
There are two main types of pile foundations: end bearing piles and friction piles. End bearing piles rely on a strong layer of soil or rock at the bottom to transfer the load of the building, while friction piles transfer the load through the friction between the pile and the soil along its entire length.
To better understand how friction piles work, consider the analogy of pushing a metal rod into a tub of frozen ice cream. The deeper the rod is inserted, the more load it can support. Similarly, the load capacity of a friction pile is directly proportional to its length.
Materials used in pile construction typically include wood, concrete, or steel. In the past, wooden piles were commonly used in areas with weak soil. However, in modern construction, wood piles are still utilized for structures like jetties, where the straight trunks of trees are essential. Wooden piles are limited in length to the size of a single tree, usually around 20 meters, as it is not possible to join two tree trunks together. The city of Venice in Italy is a prime example of a city built on wooden piles over the sea.
Concrete piles, on the other hand, are precast at ground level and then driven into the ground using a hammering process. Steel H-piles are another option that can support heavy loads and reduce construction time by eliminating the need for pile casting. Unlike concrete piles, steel piles do not require a protective coating, as the soil would scrape it away during the driving process. In areas with corrosive soil, concrete piles are preferred for their durability.
The construction of piles can be categorized into two main types: cast-in-place piles and precast driven piles. Cast-in-place piles involve hammering a thin-walled steel tube into the ground, emptying the tube of soil, placing a steel reinforcement cage inside, and pouring wet concrete into the tube to form the pile. The steel tube, also known as the casing, acts as a mold for the concrete and is removed once the casting is complete. In cohesive soils that retain their shape, a casing is not needed, which helps reduce costs.
On the other hand, precast driven piles are first cast at ground level and then driven into the ground using a pile driver. The pile driver lifts the pile into a vertical position and hammers it into the ground blow-by-blow. A steel cap protects the pile during the driving process. The pile driver functions as a crane, lifting and rotating the pile, while providing the necessary force to drive it into the ground.
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