What is piling?
Piling is the process of inserting structural piles into the ground with the purpose of giving buildings foundational support. They’re used to transfer the load from heavy structures onto hard rock or soils that have higher bearing capacity. They’re particularly useful on poorly performing earth that is unable to hold the load independently.
Piling occurs before construction work begins and is a cost-effective approach to creating deep foundations to significantly improve the life expectancy of a structure. They can be made of different materials, including wood, steel and concrete. The choice of material will depend on each individual project, whether it’s a new home, shopping complex or block of high-rises.
How does piling work?
Piling techniques vary depending on the type of pile being used, but their general job is to distribute the weight of a building more evenly on the surface, whilst offering structural support. They’re often placed into the ground using a pile driver and are inserted using hammering or vibrations.
The piling process cannot start until all other construction factors have been considered, especially the condition of the soil beneath the ground. This is because the type of soil can determine which piling technique should be used.
When is piling needed in construction?
Piling is generally required when a traditional, shallower foundation doesn’t provide enough support to bear the load of a structure. This can happen when the surrounding soil is considered to be inadequate or when a project is so large that it needs additional support.
Piling is also ideal when:
- The water table is high
- The type of soil is susceptible to losing stability
- Existing trench foundations are unstable or too expensive to remove
- Alternative methods are too pricey
Types of piles
Types of piling can be categorised by either the purpose of the design, or by the method that’s used to supply and install them. When construction workers are determining which type of piling is best for their project, they may consider:
- The depth of the excavation
- The angle at which the pile needs to be installed
- The environmental issues that may impact local residents
Some of the most commonly used types of piles include:
Driven piles (displacement piles)
Driven piles are hammered into the ground with lots of force and compact the soil mass to increase its density and bearing capacity. These piles are precast before being placed at construction sites and can be cast in many sizes to suit individual projects.
Bored piles (replacement piles)
Bored piles are installed by auguring into the ground to create a hole that’s filled with concrete. This process casts the pile into position on site, making them incredibly secure. This method is ideal for residential areas as there’s less vibration during installation.
End-bearing piles transfer the bulk of the structural load directly onto the base of the pile, after it’s been penetrated into the solid layer of earth. This essentially forms a column that cuts through weaker ground into the sturdier surface beneath.
Friction piles use their height to transfer the force a building generates into the soil. With this method of piling, the amount of load a pile can support is proportional to the length of the pile: meaning that the greater the depth, the more weight can be held.
Screw piles are fixed to the ground using their helix end, ultimately like a screw would fasten into wood. These piles are beneficial when looking to minimise damage created during installation and can often be more cost effective.
Timber piles are the oldest of all the currently used piling methods. These piles are precast off-site and are installed with the driving method. They offer a highly economical, safe and efficient solution for all structures.
Steel piles are installed using high impact or vibration hammers to break into study soil or rock. These piles can be used in temporary and permanent projects and they’re often used in time-restrictive projects because construction work can proceed without delay post-installation.
Concrete piles are often used in offshore projects, such as bridges and oil rigs. These piles support vertical structural loads and lateral wave loads and can help to stabilise complex terrain.