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Types of Pile Foundation in construction

What Are Types of Pile Foundation in construction ? .Many different types of pile foundation are used in construction, but they all have one important function: to transfer loads from a structure or building into the ground. Some pile foundation types are named after the technique used – bored pile foundations, for instance, which require the boring of large holes into the ground. Other piling methods are categorized by their intended purposes. Friction piles are an often-cited example of this, as they are designed to transfer load to the surrounding soil by friction.

Types of Pile Foundation in construction
Types of Pile Foundation in construction

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What is piling in construction?

Piling is the process of driving or boring pile foundations into the ground beneath a building that is under construction. These piles transfer loads from the structure to the ground, helping to support it. Pile foundations are often used where the ground is too weak to underpin the structure.

What are pile foundations?

Pile foundations are long, thin elements generally made of steel or reinforced concrete. They transfer the load through weak, compressible material onto more compact, less compressible stiffer soil or rock at greater depth. The deep insertion of these elements ensures a sturdy base on which the construction project can take place.

It’s important to note that the pile foundation and pile are two different things, yet they work in conjunction to ensure that piling can support strong loads. A pile foundation is typically defined as the series of columns that act as the base for structures, whereas the pile itself is the column or cylinder that aids in transferring the load to the lower subsoil.

pile foundations
pile foundations

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Where did piling come from?

As with many modern techniques, our high-tech piling systems today grew out of a clear need, hundreds and even thousands of years ago, that still exists today. Some of the first recorded examples of piling include river dwellers in Switzerland 6000 years ago, building structures on piled foundations to defend against flooding and attack, by elevating their dwellings. The Romans – inevitably – led the way with piles for shore works in Europe, and in the UK, there is proof that they used timber piles driven into the riverbed for bridges in London and Corbridge, over 2000 years ago.

In early civilisations, cities and towns wanted to build close to rivers for communication and protection, so the swampy soil needed to be fortified and strengthened with something – which is how and why piling was born. Timber piles were driven into the ground by hand, or holes were dug and filled with sand and stones. In more modern times, the ever-increasing need for buildings and infrastructure has forced authorities and development agencies to exploit land with poor soil characteristics. Piling is – as it always was – vital in our modern-day construction industry.

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Classification of Pile Foundations

Pile foundations are categorized based on different factors, including material, load transfer mechanism, and installation method.

Based on Load Transfer Mechanism:

  1. End-Bearing Piles – Transfer load directly to a strong stratum.
  2. Friction Piles – Rely on friction between the pile surface and surrounding soil.
  3. Combination Piles – Use both end-bearing and friction principles.

Based on Material:

  1. Concrete Piles
  2. Steel Piles
  3. Timber Piles
  4. Composite Piles

Based on Construction Method:

  1. Driven Piles (Displacement Piles)
  2. Bored Piles (Replacement Piles)

Read More : Structural Elements of Reinforced Concrete Buildings

Types of Pile Foundation in construction Based on Load Transfer Mechanism

End-Bearing Piles

End-Bearing-Pile-Foundation
End-Bearing-Pile-Foundation

End-bearing piles are piles that rely on the resistance of the soil or rock at the tip of the pile to support the load. They are usually driven or bored into the ground until they reach a hard layer, such as bedrock or dense sand. The length and diameter of the pile depend on the load and the soil conditions. End-bearing piles are suitable for sites where there is a clear and strong bearing layer at a reasonable depth, and where the upper layers are not too soft or compressible.

How End-Bearing Piles Work

End-bearing piles function like columns, transferring loads through weak soil to a solid stratum. The pile tip rests on a strong layer, ensuring stability.

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Advantages

  1. It experiences low settlement compared with other types of pile like floating pile. That is why multi-story buildings are mostly constructed on this type of pile.
  2. The end bearing piles are generally used in the most of the construction sites.
  3. End bearing pile can be precast to specifications.
  4. They can be prefabricated into any length, shape, and size and used on-site, hence reducing the completion time.
  5. End bearing pile goes does not experience buckling failure in weak soil except if it passes through air or water.
  6. The pile rests on firm stratum that could be stronger than the steel for the maximum design load that can be applied.
  7. The cost of pile construction can be optimized since its length can be specified based on the depth of firm soil layer.
  8. The length of the pile to be used can be easily computed based on bedrock depth obtained from soil exploration borehole records.

Disadvantages

  1. Heavy equipment is needed for the construction of end bearing.
  2. The soil surrounding the pile may adhere to the surface of the pile and causes “Negative Skin Friction” on the pile.

Friction Piles

friction-piles
friction-piles

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Friction piles are piles that rely on the friction between the surface of the pile and the surrounding soil to support the load. They are usually driven or bored into the ground to a depth that is sufficient to mobilize enough friction. The length and diameter of the pile depend on the load and the friction angle of the soil. Friction piles are suitable for sites where there is no distinct bearing layer, or where it is too deep or too weak, and where the upper layers have some frictional strength.

Functioning of Friction Piles

Friction piles rely on skin friction between the pile surface and surrounding soil to support loads. The entire length of the pile contributes to load transfer.

Where They Are Used

  • Suitable for locations with no solid bedrock.
  • Used in sandy, clayey, and loose soil conditions.

Types of Pile Foundation in construction Based on Construction Method

Driven Piles (Displacement Piles)

Driven Piles
Driven Piles

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Driven piles are the classic type of pile foundation. They can be constructed with timber, a technique centuries old and still used across the globe. In the UK, timber piling is used mainly for coastal works, sea defence and jetties. Another option is precast concrete piles, reinforced to withstand driving stresses, they are usually pre-pressed with a square or octagonal section. Lastly, there are steel piles of tubular, box, or H section. Interlocking steel sheet piles are also widely used, predominantly for wall construction.

With each of these materials, the piles are driven into the soil, pushing an equal volume of soil sideways and compacting a zone around the pile, increasing its bearing capacity. For this increase in soil strength to take place, the pore water pressures must dissipate by rapid drainage. This type of piling is not suitable for saturated or silty soils as they drain slowly and can not be compacted in the same way.

Advantages and disadvantages

The main advantages of using driven piles are:

  • Piles can be pre-fabricated off-site which allows for efficient installation once on site.
  • Driven piles displace and compact the soil which increases the bearing capacity of the pile. Whereas, other deep foundations tend to require the removal of soil which can lead to subsidence and other structural problems.
  • They are cost-effective as a wide variety of materials and shapes can be easily fabricated to specified dimensions, which can result in the need for fewer piles on site.
  • They generally have superior structural strength to other forms of foundation. Their high lateral and bending resistance makes them ideal for challenging conditions such as wind, water, seismic loading, and so on.
  • Installation usually produces little spoil for removal and disposal.

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The main disadvantages of using driven piles are:

  • Advance planning is required for handling and driving, as well as the heavy equipment on site.
  • To be able to withstand handling stresses during transportation and installation, precast or pre-stressed concrete piles must be adequately reinforced.
  • It may not be possible to determine the exact length required and so splicing or cut-off techniques may be required which has time and cost implications.
  • Driven piles may not be suitable where the ground has poor drainage qualities.
  • Driven piles may not be suitable for compact sites, where the foundations of structures in close proximity may be affected by the vibrations caused by installation.
  • Driven piles can be noisy to install and vibrations can result in complaints from neighbours, who may become aware of pre-existing problems with their own building that they then blame on piling vibration.

Bored Piles (Replacement Piles)

Bored Piles
Bored Piles

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Bored piles, also known as replacement piles or drilled piles, are constructed when large holes are drilled in the ground and filled with concrete. Bored piles are very effective as they transfer the load above ground to the deep rock and soil layers below with minimal settlement, which is ideal for supporting structures such as bridges and flood protection.

For some bored piles, the bottom of the hole is widened or under-reamed, creating a bulb at the end. A steel reinforcement cage is lowered into the hole before the concrete is placed or dropped in after the concrete has been poured.

Bored pile construction methods can vary depending on ground conditions. Within the category of bored pile foundations, the two commonly used subtypes are rotary bored piling and Continuous Flight Auger (CFA) piling:

  • Rotary bored piling is used in cases where there are significant obstructions in the ground. A temporary casing is installed by the piling rig to provide support. ‘Pile arisings’ (ground and rock removed via boring process) are removed from inside the casing, then a steel reinforcement cage is installed. At this point, the hole is filled with concrete and the casing is removed.
  • Continuous Flight Auger (CFA) piling does not require the use of temporary casing – it is the most versatile, effective and commonly used type of bored pile foundation in the UK. Once the hole has been bored, concrete is pumped in, then a steel reinforcement cage is inserted.

Advantages and Disadvantages

✅ Suitable for deep foundations
✅ Less vibration during installation
❌ Slower construction process

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Bored piles vs driven piles

As stated above, driven piles are a classic form of piling technique where a pile is driven into the soil, increasing its bearing capacity. Whereas a bored pile is constructed via drilling holes in the ground and filling with concrete.

The main difference between these two types of piles are that driven piles are formed off site and put in place on-site, whilst bored piles are cast in concrete on-site. Driven piles have the advantage of being rapid to build and use, however they create lots of vibrations, so aren’t suitable at compact sites. Bored piles are favoured as they don’t create this disturbance in soils, have higher bearing capacities and avoid seasonal disturbances such as frost penetration.

Types of Pile Foundation in construction Based on Material

Sheet Piles

Sheet Piles
Sheet Piles

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This type of pile is mostly used to provide lateral support. Usually, they resist lateral pressure from loose soil, the flow of water, etc. They are usually used for cofferdams, trench sheeting, shore protection, etc. They are not used for providing vertical support to the structure. They are usually used to serve the following purpose-

  • Construction of retaining walls.
  • Protection from river bank erosion.
  • Retain the loose soil around the foundation trenches.
  • For isolation of foundation from adjacent soils.
  • For confinement of soil and thus increase the bearing capacity of the soil.

Timber Piles

Timber Piles
Timber Piles

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Timber piles are the types of piled foundations that are placed under the water level. They last for approximately about 30 years. They can be rectangular or circular in shape. Their diameter or size can vary from 12 to 16 inches. The length of the pile is usually 20 times the top width.

They are usually designed for 15 to 20 tons. Additional strength can be obtained by bolting fish plates to the side of the piles.

Advantages of Timber Piles

  • Timber piles of regular size are available.
  • Economical.
  • Easy to install.
  • Low possibility of damage.
  • Timber pile footings can be cut off at any desired length after they are installed.
  • If necessary, timber piles can be easily pulled out.

Disadvantages of Timber Piles

  • Piles of longer lengths are not always available.
  • It is difficult to obtain straight piles if the length is short.
  • It is difficult to drive the pile if the soil strata are very hard.
  • Spicing of timber piles is difficult.
  • Timber or wooden piles are not suitable to be used as end-bearing piles.
  • For the durability of timber piles, special measures have to be taken. For example- wooden piles are often treated with preservatives.

Concrete Piles

Concrete Piles
Concrete Piles

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Pre-cast Concrete Pile

The precast concrete pile foundation is cast in a pile bed in horizontal form if they are rectangular in shape. Usually, circular piles are cast in vertical forms. Precast piles are usually reinforced with steel to prevent breakage during their mobilization from the casting bed to the location of the foundation. After the piles are cast, curing has to be performed as per specification. Generally curing period for pre-cast piles is 21 to 28 days.

Advantages of Pre-cast Piles

  • Provides high resistance to chemical and biological cracks.
  • They are usually of high strength.
  • To facilitate driving, a pipe may be installed along the center of the pile.
  • If the piles are cast and ready to be driven before the installation phase is due, it can increase the pace of work.
  • The confinement of the reinforcement can be ensured.
  • The quality of the pile can be controlled.
  • f any fault is identified, it can be replaced before driving.
  • Pre-cast piles can be driven under the water.
  • The piles can be loaded immediately after it is driven up to the required length.

Disadvantages of Pre-cast Piles

  • Once the length of the pile is decided, it is difficult to increase or decrease the length of the pile afterward.
  • They are difficult to mobilize.
  • Needs heavy and expensive equipment to drive.
  • As they are not available for readymade purchase, it can cause a delay in the project.
  • There is a possibility of breakage or damage during the handling and driving of piles.

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Cast-in-Place Concrete Piles

This type of pile footing is constructed by boring soil up to the desired depth and then, depositing freshly mixed concrete in that place and letting it cure there. cast in situ concrete pile foundation is constructed either by driving a metallic shell to the ground and filling it with concrete and leaving the shell with the concrete or the shell is pulled out while concrete is poured. Usually, round piles are used in cast-in-situ piling.

Advantages of Cast-in-Place Concrete Piles Foundation

  • The shells are lightweight, so they are easy to handle.
  • The length of piles can be varied easily.
  • The shells may be assembled at sight.
  • No excess enforcement is required only to prevent damage from handling.
  • No possibility of breaking during installation.
  • Additional piles can be provided easily if required.

Disadvantages of Cast-in-Place Concrete Piles

  • In this type of pile foundation, installation requires careful supervision and quality control.
  • Needs sufficient place on site for storage of the materials used for construction.
  • It is difficult to construct cast in situ piles where the underground water flow is heavy.
  • The bottom of the pile may not be symmetrical.
  • If the pile is un-reinforced and uncased, the pile can fail in tension if there acts an uplifting force.

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Steel Piles

Steel Piles
Steel Piles

Steel piles may be of I-section or hollow pipe. They are filled with concrete. The size may vary from 10 inches to 24 inches in diameter and the thickness is usually ¾ inches. Because of the small sectional area, the piles are easy to drive. They are mostly used as end-bearing piles.

Advantages of Steel Piles

  • They are easy to install.
  • They can reach a greater depth compared to any other type of pile foundations.
  • Can penetrate through the hard layer of soil due to the less cross-sectional area.
  • It is easy to splice steel piles
  • Can carry heavy loads.

Disadvantages of Steel Piles

  • This piling type is prone to corrosion.
  • Has a possibility of deviating while driving.
  • Comparatively expensive.

Read More : Corrosion Of Steel In Concrete

FAQs About Types of Pile Foundation in construction

1. What is the purpose of a pile foundation?

A pile foundation transfers loads from structures to deeper soil layers to ensure stability.

2. When are pile foundations required?

They are needed when the surface soil lacks adequate bearing capacity.

3. What is the difference between driven piles and bored piles?

Driven piles are hammered into the ground, while bored piles are drilled and then filled with concrete.

4. How deep can pile foundations go?

Pile depth varies based on soil conditions and structure requirements, typically ranging from 10m to 50m.

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Types of Pile Foundation in construction
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