What is Piling?
Piling is employed in the construction of bridges, buildings, and other structures when the shallow depth of the soil at the construction site cannot support the weight of the structure. Therefore, piling is used to ensure the safety of these building’s structures.
Piles are inserted into the earth up to the bedrock to hold and support the weight of the structure above it safely and firmly.
History of Piling
Piling, though not as precise as it is today, has a history dating back thousands of years. Around the 4th Century BC, ancient people used piles to build homes in places with weak soil near rivers. They often drove wooden piles into the ground to create a sturdy foundation.
Some evidence shows that lake dwellers used piling to raise their homes, providing protection from potential attackers. The elevated buildings gave them the upper hand in case of an attack.
The Romans, too, employed piling methods to build bridges in Britain. They are often considered the early users of piling techniques, some of which are still in use today, particularly in cities like Venice.
In the early days, piling was carried out using trimmed timber branches, which were driven into the ground using drivers, rams, and mauls. As time passed, techniques evolved to make piling more efficient, relying increasingly on machinery rather than manual labour.
Materials used for piles also diversified; concrete and steel became popular choices. These materials proved to be much more capable of withstanding tensile forces, compression, and bending, marking a significant advancement in piling technology.
Why is Piling Used?
If there are some forces that will affect your building structure, they will definitely have an impact on its foundation. The use of piling foundations helps in the resistance of any motions as well as the support of the building’s vertical load.
Generally, pile foundations serve the following functions:
- Ensuring the security of the structure above them.
- Improving the safety of heavy-load buildings.
- Assisting with weight distribution.
- Safely transmitting the load of the structure into the earth.
Where and When Can You Use a Pile Foundation?
Piling can be used on various construction sites because it has numerous advantages. Some of these are as follows:
- Piling is the best option in areas where uneven settlement is common due to issues with underground water tables or soil liquefaction.
- A pile foundation is essential when huge buildings are constructed on weak soil.
- In some circumstances, the subsurface water table at the construction site is so high that employing shallow foundations is impossible. When this happens, piles are preferred as they can easily be penetrated through the water until they touch the hard stratum.
- Forces like high earthquakes and winds acting horizontally on the building can have a significant impact on its foundation. Using pile foundations in areas that are more prone to earthquakes is very beneficial as they can resist pressure caused by these forces.
- The pile foundation can greatly withstand uplift forces caused by a rising water table or other factors.
- If the building’s construction is uneven, the weight on the foundations will be unevenly distributed. Using a shallow foundation in these scenarios will result in uneven settlement and serious cracks in the structure, making pile foundation the best option.
Piling Types According to Their Working Principle
The most common types of piling are listed below:
End-Bearing Piles
End-bearing piles are used to transmit superstructure load to a strong stratum with a higher bearing capacity. These piles behave like a column, crossing through weak soil and resting on a strong soil layer. Because of this, the design of this kind of pile matches the structure of a reinforced concrete column.
Friction Piles
Friction piles, also known as floating piles, primarily withstand the weight of the building by transferring the structural loads to the adjacent soil throughout their skin. The friction between the surrounding soil and the pile surface keeps the pile firmly locked in place while transmitting the loads to the soil.
These piles are especially helpful when rock strata are too deep and end-bearing piles become economically unviable. In this situation, friction piles are utilised.
Compaction Piles
A compaction pile is a sand pile that is inserted into granular soil to increase the soil’s bearing capacity. A pipe is inserted into the ground, causing the soil around it to shift laterally and get compacted, after which the pipe is gently removed and replaced with sand.
Anchor Piles
Bridges, tall buildings, and other structures subject to uplift forces are intended to be supported by anchor piles. Steel cables or rods are often used to attach anchor piles to a hard rock or a layer of dense soil. The anchor pile is driven into the ground using a pile driver, and the rod is then fastened to the building to offer additional support.
Sheet Piles
Sheet piles are intended to give lateral support to retaining walls and excavations. These piles are typically made up of steel, but reinforced concrete or timber can also be utilised. Their installation procedure is simple and quick, and they are frequently utilised in locations where there is little room for excavation.
Piling Types According to Their Construction Techniques
The three most common methods of using piling in construction are listed below:
Driven Piles
These piles are prefabricated according to the specifications and then brought to the building site. After that, they are driven into the ground using specialised hydraulic-powered hammers and jacks. These piles displace an equivalent volume of soil, strengthening the soil as a result.
Examples:
- Screw piles
- Friction piles
- Steel H-piles
- Timber piles
- Pipe piles
- Pre-cast concrete
- Steel sheet piles
Cast-in-Situ Piles
Unlike driven piles, these piles are constructed in-situ using specialised tools and techniques. In this technique, a borehole is drilled into the earth up to the required depth. After that, a steel cage is inserted for reinforcement purposes, and the concrete is poured into the hole.
Examples:
- Union meta monotube pile
- Raymond pile
- Western button pile
- Mac-arthur pile
- Swage pile
Combined Piles
The driven pile foundation procedure and the cast-in-situ pile foundation process are both used in combined pile foundations. As a result, it holds the benefits of each method. A steel shell with the same diameter as the pile is first driven into the earth. To secure the base, they then pour concrete into the shell. Engineers frequently utilise this technique to build up over water.