Different types of foundation piling can be grouped by either the purpose of their design or by the method used to install them in the ground. A wide range of pile types are available for applications with various soil types and structural requirements. Piles may be classified by their basic design function (end-bearing, friction or a combination) or by their method of construction.

Pile Classifications

Displacement: Driven Piles
Replacement: Bored Piles
An end-bearing pile transfers the bulk of its load directly to the base or toe of the pile once a solid layer is penetrated, whereas a friction pile transfers its load along the entire shaft using friction between the pile and soil to achieve the required load when a solid layer cannot be penetrated.

We can categorize foundations as shallow foundations or deep foundations. We typically use shallow foundations where the loads imposed by a structure are low relative to the bearing capacity of the soils. Think footings and masonry walls on a typical home. Deep foundations are necessary where the bearing capacity of the soils cannot support loads imposed. So we transfer them to deeper layers or to bedrock, where higher load bearing capacity can be achieved. There's several ways to construct and install the different types of piling.

Bored Piling

We installed bored piles by boring or drilling into the ground, creating a hole into which we can pour concrete. The soil needs to hold the form of the hole, long enough to pour the concrete in position. When cured the concrete becomes the piling. This method of piling is well suited for work in cities, populated areas and areas surrounding existing buildings as the vibration caused by installation is minimal. .

An open bored pile is constructed by boring into the ground and removing the auger/drill forming an open hole into which steel and concrete can be installed. Bored piling is suitable for cohesive ground with low water tables. When a pile is bored and we pour the concrete before the augers are extracted it is referred to as a CFA pile (continuous flight auger) or SFA pile (sectional flight auger).

Famous Buildings Built on Bored Piles

There are many notable buildings built on bored piles or a combination of piles. Here we list two buildings that used auger bored pilings in their construction.

TRUMP International Hotel & Tower Chicago, Illinois, USA (Read More Here)
Taipei International Finance Center, also known as Taipei 101, is located in Xinyi District, Taipei, Taiwan (Read More Here)

Engineering Bored Piles 101

Being that bored piles are used primarily in cohesive subsoils for the formation of friction piles, geotechnical engineering is heavily involved.

The key to engineering a good bored pile is, improving the skin friction interaction between the pile shaft and surrounding soil. There are too many materials to list here. But grout, polymers and bentonite are commonly used.

During the construction of bored piles, it is common practice for a geotechnical engineer to validate ground conditions besides the roughness and cleanliness of the pile sidewalls and base cleanliness.

Consumer electronics have provided inexpensive, compact cameras that engineers use to capture high resolution video while being remotely operated. When combined with LED lighting, it creates a device which can readily be used to inspect a range of construction environments including bored piles.

Types of Bored Piles

There are four types of bored piles most commonly used and listed below. there are other bore and fill type piles such as tampered bored piles. Here is a brief explanation of the four common types.

Kelly Pile-The kelly-method is used to produce uncased, partially or fully cased or slurry-supported bored piles. A drilling tool excavates the soil mounted at the tip of a telescopic kelly bar. When the fully cased pile technique is used, the in-section of the full depth casing is simultaneous to the excavation, until the final depth is reached.
Double Rotary System (DRS)-The DRS links the CFA-method with the kelly casing method. The result is a fully cased bore, produced by a continuous flight auger. The advantages of this method is where the groundwater level is high with the risk of soil collapse.
Continuous Flight Auger (CFA)-The CFA-method is a rotary drilling method which permits high drilling performance. This method employs a continuous flight auger as the drilling tool. When the final depth is reached, concrete is pumped from bottom to top through the hollow stem auger. The reinforcement is installed subsequently, where necessary, the reinforcement is assisted by vibration.
Full Displacement Pile (FDP)-The FDP-system has a key advantage over the CFA-method in that it transports virtually no drilling spoil to the surface. It is suitable in displaceable soils. The drill rod has an auger as a starter, followed by the displacement body and an extension casing. During drilling and extraction, the surrounding soil is displaced. Concreting and reinforcement is executed as in the case of the CFA-pile, being pumped from the bottom to the top.

Driven Piling

Driven piles are a displacement type of piling and are driven or hammered into the ground with the use of vibration. This method of piling is well suited for foundations in non-cohesive soils, ground with a high water table and for soils that contain contaminants.

Driven piles can be cast in position by using temporary or permanent steel casing. They can also be prepared off site by using precast piles, which can be created using steel, timber or wood, concrete or a combination of these.

Driven piles are commonly used to support buildings, tanks, towers, walls and bridges, and can be the most cost-effective deep foundation solution. They can also be used in applications such as embankments, support of excavation, retaining walls, bulkheads, anchorage structures and cofferdams.

Types of Steel Driven Piles

H Piles-Hot rolled sections are used in the construction. Pile driving contractors weld them together to increase the length.
Steel Box Piles-Four steel sheets welded together to create box shape pile or sheet piles welded together to create a hollow box section can be used in the construction. The inner core can be filled with concrete to improve the lateral, bending, and torsional stiffness.
Steel Railed Piles-Old rails have been used as steel piles. Three rails are welded at the top or bottom. Butt- welding is used to join two sections to increase the length of the pile. Since these piles are from abundant materials, the cost will be less. Though not commonly used, it could be considered as green construction as we reuse the materials.
Precast Concrete Driven Pile Foundations-The most widely used type of driven piles in the construction. Mainly there are two types of precast piles.Normal reinforced precast piles and prestressed concrete piles.

Methods for Installing Driven Piles

There are two common methods to drive piles. The sledge hammer approach and the vibration approach.

The conventional method: Apply a force on the pile by letting a weight fall into the pile. The applied load shall be calculated based on the free-fall height of the weight. It shall be made sure that the applied load will not exceed the capacity of the driven pile.

Hammer driving methods: There are three types of driving methods. They are:

Diesel Hammer Driving
Air Hammer Driving
Vibratory Hammer Driving

Screw or Helical Piling

Screw piles use circular hollow galvanized steel pile shafts with one or more steel helices attached to them and helical pile driving companies fasten them into the ground much like a screw is fastened into wood.

This type of pile minimizes the spoil created by installation and sometimes may provide a more sustainable and cost-effective alternative to other piling methods.

A screw pile may have over one helix (also called a screw), depending on the usage and the ground conditions. With more helicals specified by the geo-engineer or civil engineer if a higher load is required or they encounter softer ground.

Types of Helical Piles

Every foundation construction project is unique. Each type of structure will require a foundation specifically engineered to account for the size of the job and the ground on which it’s built. For this reason helical pile designs span a variety of shapes and sizes to accommodate different applications. With variables such as soil type, soil profile depths, pile loading type, pile capacity requirements, the type of structure to be supported

Solid Square Shaft-The square shaft is typically solid and capable of large axial compressive loads. The solid shaft is continuous at each extension and carries the load down through to the end of the pile. Square shaft extensions can also used in a variety of tension applications.

Round Shaft Pipe-The round shaft pipe helical pile provides a much wider diameter than most square shaft piles. The wider cross section provides better structural capacity where large moments, lateral loading, or buckling can be present.

Combo Pile-Typically a combo pile has a square shaft lead, followed by round shaft extensions. These types of helical piles are used primarily in compression applications where layers of hard soil are located deep under a softer surface soil. Square/round combo piles are often chosen for high water tables, grout restricted sites or for sites with soils that make them a more economic choice than a grouted pile configuration.

Grouted Square Shaft-All square shaft piles can be fitted with accessories to add a grouted casing. This casing is typically 5” to 8” in diameter and can be cased in PVC or steel pipe, or just grout. The grout also creates skin friction with the soil that can help the compression and tension capacity of the pile. The larger cross section improves lateral capacities, bending moment, and buckling resistance strength when compared to the slender square shaft pile on its own.

Choosing the right type of helical pier design needs to be done by an expert! These basic explanations offer guidance for which types of helical piles are appropriate for different foundation projects, but there are variables that go into making an educated decision.

Sheet Piling

Sheet piles, a type of driven pile, are constructed with a series of interlocking steel sheets. However, sheet piles may be made up of wood, concrete or steel. Common sheet piling is steel piles driven side by side into the ground to form a continuous vertical wall for retaining soil.

They can be used to create permanent or temporary retaining walls on construction sites where large excavations are required. When used for temporary trench safety, they act as supports for construction much like a scaffold is used temporarily for work being done up high. Sheet pile is used to keep workers safe while working below grade.

Other common permanent uses are:

bulkheads
boat ramps
wharfs
retaining walls,
land reclamation,
underground structures such as car parks and basements
riverbank protection
seawalls

This method of piling can be very cost effective on sites where temporary soil retention is necessary as the sheets can be removed and used again on different sites once the ground works have been completed.

Caissons and Cofferdams: Caissons are generally used as the means to complete new construction, and may act as a cofferdam of sorts while the construction is ongoing. Cofferdams however, are not part of the permanent structure, and are typically employed to perform repairs or maintenance on the structure.

Types of Sheet Piling: Steel sheet pile is a rolled steel section consisting of a plate called the web with integral interlocks on each edge. The interlocks consist of a groove, one of whose legs has been suitably flattened. This flattening forms the tongue which fits into the groove of the second sheet. Commonly used sheet piles can be broadly divided into the following four categories,

Straight or Flat web type
Pan-web type
U- web piles
Z web type

Types of Flat Webs Piles

AS Sheet Piles
PS Sheet Piles

Flat sheet piles are formed in circles and arcs to create gravity cells. The cells are held together through the tensile strength of the interlock. These piles allow a wide range of design shapes.

Types of U Web Piles

AU/PU Sheet Piles

U sheet piles retain soil and water just like Z piles with one important difference: U piles have the interlock on the neutral axis. The placement of the lock in the centerline of the wall reduces the efficiency of the section and can cause reduction of section properties because of shear transfer problems. Making it an excellent option for environmental applications.

Types of Pan Web (Shallow and Deep)

SKL Sheet Piles
SKS Sheet Piles

The pan type sections are often used on drainage ditches, retaining walls on private homes, and golf courses.

Types of Z Web Piles

NZ Sheet Piles
AZ Sheet Piles
PZ Sheet Piles
SCZ/SKZ Sheet Piles

Retaining walls, cofferdams, parking garages, environmental barrier walls, and bulkhead walls for ports are just a few of their varied uses.

Special shapes and sizes of steel sheet piles are manufactured for meeting the requirement of the project at hand. In general, straight web type of piles are used where the piles are liable to he subjected to tensile forces and interlocking strength is of prime importance (cofferdam); Arched-web type are used where the piles are required to resist bending stresses (cantilever retaining walls) and Z-Steel piles:

In general, straight web type of piles are used where the piles are liable to he subjected to tensile forces and interlocking strength is of prime importance (cofferdam); Arched-web type are used where the piles are required to resist bending stresses (cantilever retaining walls) and Z-web (Common) type of piles arc used where the piles are required to resist bending stresses of very large magnitude.

A wall made from properly driven sheet piles leaks very little, therefore steel sheet piling is used with many advantages in the construction of deep cofferdams. They are commonly used in coastal defense and erosion works which are likely to be subjected to moving water or tidal action.

Steel Pipe Piles

Driven steel pipe piles are installed using impact or vibration hammers to a design depth or resistance. Small diameter tube piles to large diameter steel caissons can be driven to support the foundation project. Driven pipe piles gain geotechnical capacity efficiently by displacing the soil around the shaft and compacting the soils at the toe during installation. Steel pipe pilings can be driven either closed or open ended. Either a high frequency oscillating hammer or a percussion hammer provides the energy to drive the piles.

Because of its prime material strength, a steel pipe pile can be driven with powerful impact to ensure that it reaches a hard bearing stratum, thereby realizing large bearing capacity. Having high yield strength and bending resistance, steel pipe piles offer strong resistance to lateral loads in the event of earthquakes.

Types of Pipe Piling

While all of the different piling methods involve driving pipes, different soil conditions and structural needs lend themselves better to different types of pipe piles. Here is an overview of some of the most common:

Unplugged Open-Ended – These pipes are completely open ended. After installation the ground level should be the same inside and outside the pipe. They transfer their load to the soil primarily through friction.

Plugged Open-Ended – These have a plug on the bottom end of the pipe. This causes the soil inside the pipe to be a precise amount lower than outside the pipe.

Bottom Plate – This is one of two common plugged piles. In this case a steel plate is welded to the lower end. The plate is intended to create compression and increase friction to reduce sliding. These are used on rocky terrain where a minimum layer of soil exists between the rock and the pile.

Steel Pipe with Rock Shoe – This is the other common plug. Rock shoes serve the same function as steel plates, but they are used when the pile comes directly in contact with a rock surface. The equipped shoe must be able to support the entire load, and it will prevent any sliding along the rocky surface.

Franki Pipe Pile – Franki piles are intended to be permanent. They are plugged with a moist concrete filling and can withstand much stronger driving impact than their counterparts.

Pipe piling comes in a wide range of diameters and wall thicknesses and is one of the most versatile deep foundation pile types. When ground pressure is high, it can be filled with concrete to add strength to smaller wall thickness pipe piles.

Mini or Micro-Piling

Mini piles, also known as micro piles, typically range in sizes from 4”-16” in diameter. What distinguishes mini piles from other pile types, however, has more to do with how and where they are installed than just the pile size itself.

In locations with restricted access, a micro pile contractor will use smaller sized piling rigs that are required in order to install piles on sites where traditional piling rigs could not operate. This opens up many options for commercial & domestic development in the city.

Micro-piles have a wide range of uses and are becoming a more mainstream method of supporting and re-supporting foundations, seismic retrofits, stabilization of slopes and even earth retention. Micro-piles are usually designed in small clusters or groups, with each typically carrying an equal amount of load.

Mini-piles are an ideal pile for complex sites where low vibration or low noise levels are required, or where limited access, such as low headroom and drilling, is difficult. The unique characteristics of micropiles make them a perfect solution when other deep foundation methods are not suitable.

Advantages of Micro-Piles

Micropiles can be installed using small equipment, getting into confined or small spaces. No harmful vibrations or noise to surrounding structures. Minimizes soil spoil generation on contaminated sites and other sensitive areas.

Types of Micropiles

Hollow Bars -In collapsing soils, the use of hollow bars to produce micropiles is ideal. Where open hole drilling may be limited in depth or temporary casing is required, hollow bars offer a single step process of grouting and reinforcing. In addition, higher values of ground to grout bond have resulted from the use of this method. The smaller, and often less expensive equipment, used with the hollow bar system allows for lower project costs and makes it easier for less specialized general contractors to use. This system is also perfect in sites with limited access or low headroom.
Threaded Micropile -Depending on the type of Micropile constructed, the capacity is developed through skin friction (the bond between grout and soil), bearing conditions and the strength of the casing/bar.

Timber or Wood Piling

Timber piles are the oldest of all the commonly used piles. Properly applied, they are a highly economical, efficient and safe foundation solution, both for temporary and permanent structures. This can be justified by several historical buildings founded on timber piles that have been in operation for thousands of years. Timber piles applied for the purposes of permanent structures are pressure-treated or have a corrosive resistant coating applied.

Commonly used on wharfs, docks, piers and beach houses, timber piles are the economical foundation base for these lighter structures.

Famous Places Built on Timber Piles

Venice-The Venice lagoon is all mud. There is no rock to construct on, not even soil. So, if you want to build stone houses and palaces that weigh hundreds of tons, you have to follow an ingenious and thorough strategy.

Venice was built by driving long pointed poles of wood; oak, larch, or pine, straight down into the seafloor. They lay out two layers of horizontal planking. Over that, they put layers of stone that made up for the foundation of the city. This technique is ancient, and the method existed even as long ago as in the days of the Roman empire. The Venetians just improved and developed it.