What Is Piling in Construction? Our Piling Experts Explain

In this article we look at what ‘piling’ means, and describe the different types of piling, particularly comparing bored piling and driven piling, along with an examination of sheet piling. We also cover the different types of piling materials commonly used.

What does piling mean?

Piling is the process of boring or driving pile foundations into the ground underneath a building or structure that is under construction.

Pile foundations are usually deep foundations, and are often used where there are heavy structures on weak soil, or in areas with soil liquefaction or high groundwater table, as well as areas prone to soil erosion and scouring. Pile foundations provide stability in areas prone to soil liquefaction, where the soil loses strength due to earthquake shaking or other dynamic forces. They transfer heavy loads from structures through the weak liquefied soil to deeper, more stable layers of soil or bedrock, ensuring the structure remains stable. Pile foundations can resist horizontal and uplift forces caused by soil liquefaction, maintaining the integrity of the foundation.

In cases where the groundwater table is high, pile foundations can penetrate through the water-affected soil, reaching firm layers below, which is not possible with shallow foundations. By reaching the hard strata below the liquefied soil, pile foundations prevent excessive settlement and potential damage to the structure.

Differences between bored piling and driven piling

Piles can be inserted into the ground in various ways. Traditionally these methods are classified as either ‘driven piling’ or ‘bored piling’.

Driven piles are pre-manufactured and then driven into the ground using heavy machinery like a pile hammer or vibratory driver. This allows quick installation and immediate load-bearing capacity once driven. They are commonly made from concrete, steel, or timber, and are suitable for projects where the soil is not too hard and where vibrations caused by driving do not affect nearby structures. Driven piling displaces soil laterally, which can increase the density of surrounding soil.

Bored piling involves drilling a hole into the ground to the required depth, placing reinforcement, and then filling the hole with concrete. As a result, they primarily involve concrete, with reinforcement bars placed inside the drilled hole. Bored piling minimises vibrations and noise, making it suitable for urban areas or where adjacent structures are sensitive to vibrations. Bored piling involves excavating soil from the ground, which can then be replaced with concrete, causing less displacement of surrounding soil. They are also used in situations where high groundwater tables or hard strata are present.

What is sheet piling?

You may also have heard of ‘sheet piling’. Sheet piling involves driving thin, interlocking sheets of steel or other materials into the ground to form a continuous barrier. The sheets are driven into the ground using vibratory hammers, hydraulic presses, or drop hammers. This method is primarily used to retain soil or water, create underground walls, and support excavations. Steel sheet is the most common material due to its strength and durability. However, sheets can also be made from vinyl, plastic, or composite materials depending on the project requirements. The sheets typically have interlocking edges that form a tight barrier, ensuring stability and minimising seepage.

Some specific examples of its application include:

• Water retention: Used to create cofferdams, which are temporary enclosures to keep water out of a construction site.
• Earth retention: Employed in the construction of retaining walls to support excavations and prevent soil collapse.
• Environmental barriers: Used in containment walls to prevent the spread of contaminated materials or groundwater.

The advantages of sheet piling include:

• Speed: Quick to install, making them suitable for projects with tight timelines.
• Adaptability: Can be used in various soil conditions and depths.
• Re-usability: Steel sheet piles can be extracted and reused in other projects, providing cost savings.

The disadvantages of sheet piling include:

• Noise and vibrations: The driving process can cause significant noise and vibrations, which might be disruptive in urban areas.
• Corrosion: Steel sheet piles are prone to corrosion and may require protective coatings or treatments to extend their lifespan.

Different types of piling materials

We have outlined some major methods of piling above.

Lastly, we look at the different types of materials that are commonly used.

• Timber Piles: Timber piles are suitable for temporary structures or in areas where timber is readily available and cost-effective. They are usually driven into the ground using a pile hammer.
• Steel Piles: Steel piles are suitable for heavy structures and deep foundations. They rate highly in strength, durability, and can be driven to great depths. They are typically driven using a pile hammer or vibration.
• Concrete Piles: Concrete piles are made from precast or cast-in-place concrete, and can include driven piles and bored piles. In driven piling, precast concrete piles are driven into the ground using a pile hammer. In bored piling, holes are drilled, reinforcements are inserted, and the holes are filled with concrete.
• Composite Piles: These are a combination of two or more materials, such as concrete and steel, and are used in specialised situations where specific properties of different materials are required. They combine the benefits of different materials, like the strength of steel and the durability of concrete. Composite piles can be driven or bored, depending on the materials used and the design requirements.