What Is Foundation?
Important Point
All engineered construction work resting on the earth must be carried by some interfacing element called a foundation.
The foundation is part of an engineered system that transmits to, and into, the underlying rock and soil the loads supported by the foundation and its self-weight.
The resulting soil stresses except at the ground surface are in addition to those presently existing in geological history and the earth mass from its self-weight.
The term superstructure(all structure) is commonly used to describe the engineered part of the system bringing Tthe load to the foundation, or substructure.
The term superstructure has particular significance for buildings and bridges; however, foundations also may carry only machinery, industrial support equipment (tanks, towers, pipes ), act as sign bases, & the like.
For it is better, for these reasons to describe a foundation the engineered system that interfaces the load-carrying components to the ground.
It is evident based on this definition that a foundation is an essential part of the engineering system.
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Type of Foundation, Use of Foundation, Application soil Conditions (Piling for Foundation)
| Foundation type | Applicable soil conditions | Use |
| Shallow foundations (generally D/B ≤1) | ||
| Spread footings, Wall footings | Any situations where bearing capacity is adequate for the applied load.May use on a single stratum; secure layer over a soft layer or soft layer over firm layer. Check settlements from any source. | Individual columns, walls |
| Combined footings | Same as for spread footings above | Two to four columns on the status or space are limited |
| Mat foundations | Soil bearing capacity is generally < for spread footings, over half the plan area, would be covered by spread footings. Check settlements from any source. | Heavy column loads; Several rows of parallel columns; use to reduce differential settlements |
| Deep foundations (generally Lp/B ≥ 4 +) | ||
| Pile Floating | Surface and near-surface soils with have the low competent soil and, bearing capacity is at great depth. Sufficient skin resistance can be developed by Pile to Soil perimeter to carry anticipated loads. | In groups of 2+ supporting a cap which interfaces with column(s) |
| Pile Bearing | Competent soil for point load is in a practical depth (8-20 m); Surface and near-surface soils not relied on for skin resistance | Same as for floating pile |
| Drilled piers or caissons | Same as for piles. May be floating or point-bearing (or combination). Depends on depth to competent bearing stratum | Use fewer; Same as for piles; For large column loads |
| Retaining Structures | ||
| Retaining walls, bridge abutments | Any type of soil but a specified zone in the backfill is usually of controlled fill | Permanent material retention |
| Sheeting structures (sheet pile, wood sheeting, etc.) | Retain any soil or water. Backfill for waterfront and cofferdam systems is usually granular for higher drainage | Permanent or temporary for excavations, marine cofferdams for river work |
Also, read: What Is Traversing in Surveying | Types | Method | Definition
What Is Pile Foundation?
The use of piles as a foundation can be traced since olden times. The art of driving piles was well-established in Roman times, and the details of such foundations were recorded by Vitruvius in 59 AD Today, pile foundation is much more common than any other types of deep foundation.
Modem pile driving started with the first steam pile drivers, invented by Nasmyth in 1845. Piles may be classified as follows:
Classification Based on Function
Based on the use or the function, piles may be classified as:
- End bearing pile (See Figure a)
- Friction pile (See Figure b)
- Compaction pile (See Figure c)
- Tension pile or uplift pile Anchor pile (See Figured)
- Fender pile and dolphins (See Figure a)
- Batter pile (See Figure f)
- Sheet pile (See Figure g)
1. End Bearing Piles:
This type of piles is used to transfer load through water or soft soil to a suitable bearing stratum.
2. Friction Piles:
This type of piles is used to transfer loads to a depth of a friction load-carrying material using skin friction along the length of the piles.
Friction pile is a kind of pile foundation. This type of pile utilizes the frictional resistance force between the pile surface and adjacent soil to transfer the superstructure load.
Depending on the subsoil strata condition, resistance force due to friction can develop in a definite pile length of on the full length.
3. Compaction Piles:
Compaction is used to compact loose granular soil, thus increasing their bearing capacity. The compaction piles themselves don’t carry any load. Hence they may be of weaker material-sometimes of sand only.
Driven to compact the soil, the pile tube, is gradually taken out and sand is filled in its place, thus forming a ‘sandpile.’
4. Tension or Uplift Piles:
This type of piles anchor down the structures subjected to uplift due to hydrostatic pressure or due to overturning moment.
5. Anchor Piles:
This type of piles provides anchorage against horizontal pull from sheet piling or other pulling forces.
6. Fender Piles and Dolphins:
This type of piles is being used to protect waterfront structures against the impact of ships or other floating objects.
7. Sheet Piles:
These piles are commonly used as bulkheads, or as an impervious cutoff to reduce seepage and uplift under hydraulic structures.
8. Batter Piles:
This type of piles is used to resist large horizontal or inclined forces.
Classification of Piles Based on Materials
- Concrete Piles:
- Precast
- Cast-in-situ
- Driven piles: Cased or uncased
- Bored piles: Pressure piles and under-reamed piles.
- Timber Piles:
- Steel Piles:
- H-piles.
- Pipe pile.
- Sheet pile.
Classification of Piles Based on Composition.
- Composite Piles:
- Concrete and timber.
- Steel and Concrete.
1. Precast Concrete Piles:
The precast concrete piles are commonly used for a maximum design load of near about 80 tonnes, except for large pre-stressed piles.
They need to be reinforced to withstand handling stresses.
They require space for storage and casting, more time to set and cure before installation and heavy equipment for driving and manging.
They also incur a high cost in cutting off the extra length or adding more distance.
2. Cast-In-Situ Piles:
The cast-in-situ piles are commonly used to get a maximum design load of 75 tonnes, except for compacted, pedestal piles.
They’re installed by pre-excavation, therefore eliminating vibration because of driving and the handling stresses.
3. Under-Reamed:
The under-reamed pile is a particular type of bored pile having an increased bulb or diameter at some point in this length, to anchor the expansive foundation soil subjected to alternate contraction
4. Timber Piles:
Timber piles have a small bearing capacity and aren’t permanent unless treated.
They’re prone to damage from hard-driving, and shouldn’t be driven through hard stratum or boulders.
Composite piles are suitable which in the upper part of a pile is to project above the water table.
This type of pile consists of a lower portion of untreated timber and an upper portion of concrete.
5. Steel Piles:
5.1. H-Piles:
Steel H piles (designated as HP) are suitable for penetrating rock as well as for driving through hard and resistant materials.
These piles displace a minimum of soil mass when driven through it and, therefore, can be easily driven through dense material without causing soil heave.
These piles can carry loads in the range of 80 kips (356 kN) to 240 kips (1068 kN) and have lengths in the range of 40ft (12m) to 100 ft (30m).
The maximum stresses in the pile section should not be more than 12,000 psi (82.7 M Pa) or as per the allowable code or specification for the job.
Steel H piles are generally driven through soft soils to hard-bearing strata.
The classic case of danger for these piles driven through loose materials to hard, uneven rock is that these piles generally get demolished at their ends, resulting in questionable end-bearing capacity.
These piles should, therefore, be protected by attaching hard steel points at their ends.
Associated Pile Fitting Corp. (1985) cites a Federal Highway Administration Ohio test case where HP 10 x 42 piles were driven to hard limestone.
None of the piles that had APF cast steel points experienced damage despite hard-driving with up to 50,000 ft-lb hammer energy. In contrast, all piles driven without point protection got damaged even by driving energy of an 8700 ft-lb hammer.
5.2. Pie Piles:
Pipe piles have two main advantages: (l) the soil within the pipe can be easily taken out since there are no obstructions for cleaning out tools (e.g., no corners), and (2) the circular shape minimizes drag from waves and current forces in deep waters.
Pipe piles can also be inspected for any damage and/or deviation from plumb by lowering a light source within the hollow section.
As shown in Figure 2.7, pipe piles can also be fitted with end caps in areas of hard-driving.
A typical type of pie foundation with tip fitting
Where the hard-bearing strata are inclined or sloping, the flat plate at the end of the pipe may cause uneven stresses on the pipe pile resulting in stress concentration and crippling of the pile.
In such situations, conical points, as shown on the pile on the right in Figure 2.7, arc used to distribute the stress around the pipe.
Pipe piles are always filled with concrete after driving in the U.S.A. This gives the piles a higher section modulus and rigidity.
The pile’s arc generally economical in the range of 40 to 80 ft (12 to 24 m) and can carry loads as high as about 250 kips (1115 kN).
Pipe piles are most suited where the overburden is soft clays, silts, and loose-to-medium dense sand and is underlain by dense-bearing granular material. They also have successfully been installed in layered soils.
For example, Lee et al. (1984) describe a foundation system for the Shangri-La Hotel on the bank of Chao Phraya River in Bangkok, Thailand, which, among other facilities, also consists of a 27-story tower block.
The foundation soils consist of the soft Bangkok clay from the surface down to about 43 ft (13 m) underlain by alternating layers of stiff clay and sand.
Pumping of water from the sand layers has reduced piezometric head in the stiff clay and sand layers causing ground subsidence as much as 4 in./yr (10 cm (yr) in Bangkok.
Pile foundations designed to rest on dense sand layers will, therefore, be subjected to negative (downward) skin friction due to subsidence of surrounding clay layers that are undergoing consolidation.
The foundation system consisted of installing 24-in. (600 mm) diameter open-ended steel pipe piles.
The installation procedure consisted of auger-pressing the pile through clay layers and through the near-surface sand layer.
Then the piles were driven with a K45 hammer with a drop height of about 8 ft (2.5 m) until a set of about 0.04 in. (1 mm) per blow was achieved.
At this time, the piles were at about 180 ft (55 m) to 190 ft (58 m) depth below ground surface.
To reduce negative skin friction, some pipe pile sections that were to him in the settling clay layer depths were coated with a bitumen slip layer that was protected by a polyethylene layer.
Remaining pile lengths (sections) were left uncoated to mobilize the skin friction. These piles thus supported the imposed loads by mobilizing skin friction and end bearing in lower stiff clay and dense sand.
Pipe piles can be used as friction piles, end-bearing piles, and a combination of friction and end-bearing or even rock-socketed piles.
They are also useful for marine structures where large diameter pipes can resist lateral forces in deep waters.
Also, read: Dynamic Vs Kinematic Viscosity (Difference & Definition)
5.3. Any Other Type of Composite:
In the other type of composite piles, steel piles are attached to the lower end of the cast-in-place concrete pile.
This type is used in a case where the required length of piles is greater than that available for the cast-in-place type.
Another type of steel piles that have been used to support light loads arc called screw piles.
These piles consist of installing by screwing the helix steel sections down into the ground by applying the torque without digging into the ground.
The main advantage of this type of piles is that the structure or the equipment can be placed on the foundation immediately after the piles have been installed without having to return to the job site after the concrete has cured.
These piles can be installed in all soil types and have been used in several countries for mast and tower foundations.
As per the above figure gives examples of some typical application of these pile types that have been used in the past.
These piles are mostly used to support lightly loaded foundations.
All the above type of foundation (Piling Foundation Types).
Also, read: What is Chain Surveying (Principal, Procedure, Method, Instrument)
Characteristics of Different Types of Foundation
In this section, the mechanisms of resistance of an individual foundation and a pile group are discussed.
The function of different types of foundations is also addressed.
Complex loadings on top of a foundation from the bridge structures above can be simplified into forces and moments in the longitudinal, transverse, and vertical directions, respectively (As per below figure).
Resistances of an individual foundation
Longitudinal and transverse loads are also called horizontal loads; longitudinal and transverse moments are called overturning moments; a moment about the vertical axis is called torsional moment.
The resistance provided by an individual foundation is categorized in the following (also see above figure).
- End-bearing.Vertical compressive resistance at the base of a foundation; distributed end-bearing pressures can provide resistance to overturning moments;
- Base shear. Horizontal resistance of friction and cohesion at the base of a foundation;
- Side resistance Shear resistance from friction and cohesion along the side of a foundation;
- Earth pressure: Mainly horizontal resistance from lateral Earth pressures perpendicular to the side of the foundation;
- Self-weight Effective weight of the foundation.
Both base shear and lateral earth pressures provide lateral resistance of a foundation, and the contribution of lateral earth pressures decreases as the embedment of a pile increases.
For long piles, lateral earth pressures are the main source of lateral resistance. For short piles, base shear and end-bearing pressures can also contribute part of the lateral resistance.
As per below table lists various types of resistance of an individual pile.
For a pile group, through the action of the pile cap, the coupled axial compressive and uplift resistance of individual piles provides the majority of the resistance to the overturning moment loading.
Horizontal (or lateral) resistance can at the same time provide torsional moment resistance.
The Resistance of an Individual Foundation
| Types of Foundation | Types of Resistance | ||||
| Vertical Compressive Load (Axial) | Vertical Uplift Load (Axial) | Horizontal Load (Lateral) | Overturning Moment (Lateral) | Torsional Moment (Torsional) | |
| Spread footing (also see Chapter 31) | End bearing | – | Base shear, lateral earth pressure | End bearing, lateral earth pressure | Base shear, lateral earth pressure |
| Individual short pile foundation | End bearing; side friction |
Side friction | Lateral earth pressure, base shear | Lateral earth pressure, end bearing | Side friction, lateral earth pressure, base shear |
| Individual end-bearing long pile foundation | End bearing | – | Lateral earth pressure | Lateral earth pressure | – |
| Individual frictional long pile foundation | Side friction | Side friction | Lateral earth pressure | Lateral earth pressure | Side friction |
| Individual long pile foundation | End bearing; side friction |
Side friction | Lateral earth pressure | Lateral earth pressure | Side friction |
| Anchor | – | Side friction | – | – | – |
A pile group is more efficient in resisting overturning and torsional moments than an individual foundation.
As per the above table summarizes functions of a pile group in addition to those of individual piles.
Additional Foundation of Pile Group Foundations
| Type of Foundation | Type of Resistance | |
| Overturning moment (Lateral) | Torsional moment (Torsional) | |
| Grouped spread footings | Vertical compressive resistance | Horizontal resistance |
| Grouped piles, foundations | Vertical compressive and uplift resistance | Horizontal resistance |
| Grouped anchors | Vertical uplift resistance | – |
A pile group is more efficient in resisting overturning and torsional moments than an individual foundation.
As per the above table summarizes functions of a pile group in addition to those of individual piles.
Tension Pile
Tension piles, also known as uplift piles or anchor piles, are a type of pile foundation that is used to resist uplift forces that might otherwise cause it to be extracted from the ground. Uplift forces can develop as a result of hydrostatic pressure, seismic activity or overturning moments.
Pile Foundation Details
A pile foundation is defined as a series of columns constructed or inserted into the ground to transmit loads to a lower level of subsoil. A pile is a long cylinder made up of a strong material, such as concrete. Piles transfer the loads from structures to hard strata, rocks, or soil with high bearing capacity.
Pile Foundation Types
Depending on their function, piles are classified as bearing piles, friction piles, friction-cum-bearing piles, batter piles, guide piles, and sheet piles. Based on the composition of materials, piles are classified as timber piles, concrete piles, sand piles, or steel piles.
Macarthur Pile
A patented pile formed by driving a steel shell into the ground to the required depth, putting in small quantities of concrete, and hammering them down so as to force the concrete into the earth beyond the point of the shell; thus enlarging the end and greatly increasing the bearing area.
Advantages of Pile Foundation:
- This can be pre-ordered.
- You can get it customized.
- Reduced construction time.
- Suitable for all sizes of land.
- Suitable for deep installations.
- Best for wetlands.
- Long-lasting.
- Good for places where drilling and creating holes are tough.
Disadvantages of Pile Foundation:
- A pile gets quickly damaged when driving through the stones and boulders.
- Piles can be attacked by marine borers in saltwater.
- A pile cannot be above ground level.
- It is very difficult to know the actual required length in advance.
Uses of Pile Foundation:
Pile foundations are principally used to transfer the loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth, increasing the effective size of a foundation and resisting horizontal loads.
Piling Techniques for Building Foundations
There are a four main types of pile foundation, each with its own method of construction:
- Driven piles.
- Bored piles.
- Driven and cast-in-situ piles.
- Aggregate piles.
Cost of Piling for Residential Foundations
Costs vary by material: Wood: $13–$20 per linear foot. Concrete: $30–$60 per linear foot. Steel hollow: $20–$40 per linear foot.
Piling Companies for Commercial Foundations
If you are looking for piling companies that specialize in commercial foundation projects, here are a few options you can consider:
- Keller Group: Keller is a global leader in geotechnical solutions and offers piling services for commercial projects. They have extensive experience in various piling techniques, including driven piles, bored piles, and auger cast piles.
- Trevi Group: Trevi is another prominent piling company with expertise in commercial foundation projects. They provide a range of piling solutions, including driven piles, micropiles, and diaphragm walls. Trevi has completed numerous commercial construction projects worldwide.
- Bauer Group: Bauer specializes in deep foundation techniques and has a strong presence in the commercial sector. They offer services such as bored piles, CFA (continuous flight auger) piles, and secant pile walls. Bauer has a track record of successfully delivering complex commercial foundation projects.
Piling Solutions for Unstable Soil Foundations
When dealing with unstable soil foundations, it is important to choose appropriate piling solutions that can provide stability and support. Here are a few piling techniques commonly used for unstable soil conditions:
- Micropiles: Micropiles, also known as mini piles or pin piles, are slender piles that are drilled and grouted into the ground. They are suitable for unstable soils because they can be installed through weak layers and into more stable strata. Micropiles offer high load-bearing capacity and are effective in areas with limited access or overhead restrictions.
- Soil Nailing: Soil nailing is a technique that involves reinforcing the unstable soil using closely spaced, grouted soil nails. These nails provide lateral support and increase the overall stability of the soil mass. Soil nailing is often used for retaining walls and slope stabilization in areas with loose or weak soils.
- Jet Grouting: Jet grouting is a ground improvement method that involves the injection of high-pressure grout into the soil, creating a cemented column. This technique is particularly useful for stabilizing loose or cohesionless soils by increasing their strength and stiffness. Jet grouting can be performed in restricted spaces and can improve the bearing capacity of the soil.
Deep Foundation Piling Techniques
Deep foundation piling techniques are used in construction to transfer structural loads from buildings or other structures to deeper, more stable soil layers or rock formations. These techniques involve driving or drilling long, slender columns called piles into the ground. Here are some commonly used deep foundation piling techniques:
- Driven Piles: Driven piles are installed by forcefully driving them into the ground using impact hammers or vibratory drivers. The most common types of driven piles include:
- Timber Piles: These are wooden piles that are relatively inexpensive but are less commonly used today due to their susceptibility to decay and insect damage.
- Concrete Piles: Concrete piles are made of reinforced concrete and are commonly used in a variety of construction projects. They offer good load-bearing capacity and durability.
- Bored Piles: Bored piles, also known as drilled piles, are created by drilling a hole into the ground and then placing reinforcing steel and concrete into the hole. Bored piles are commonly used when soil conditions are difficult for driving piles or when the design requires large-diameter piles. Some types of bored piles include:
- Augered Piles: These piles are formed by rotating a continuous flight auger into the ground, removing the soil, and then filling the hole with concrete.
- Cased Piles: Cased piles are formed by drilling a hole with a temporary steel casing to stabilize the sides of the borehole. After reaching the desired depth, the casing is filled with concrete.
- Micropiles: Micropiles, also known as mini-piles or pin piles, are small-diameter piles typically ranging from 100mm to 300mm. They are used in areas with limited access or where the soil conditions are challenging. Micropiles are installed by drilling a hole and then inserting steel reinforcement, which is grouted in place.
Types of Piles
Haemorrhoids can be grouped into four main types: internal haemorrhoids, prolapsed haemorrhoids, external haemorrhoids, and thrombosed haemorrhoids.
Tension Pile Foundation
A tension pile foundation, also known as a tension pile system, is a type of foundation used to support structures subjected to uplift or tension forces. It is primarily used in situations where the soil conditions are not suitable for traditional foundation types or where uplift forces need to be counteracted.
What Is Pile Foundation?
Pile foundation, a kind of deep foundation, is actually a slender column or long cylinder made of materials such as concrete or steel, which are used to support the structure and transfer the load at desired depth by either end bearing or skin friction.
What Is Piling Foundation?
A piling foundation, also known as a deep foundation, is a type of foundation system used to transfer structural loads from a building or structure to deeper, more competent layers of soil or rock. It is employed when the upper layers of soil are weak or unstable, and it provides a stable and secure base for the structure.
What Is Skin Friction in Pile Foundation?
Introduction. The skin friction on a pile is caused by the relative movement on the interface between the pile and the soil. By definition, if the pile settles faster than the adjacent soil, the skin friction is positive; if the soil settles faster than the pile, the skin friction is negative (NSF) [1].
End Bearing Pile
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.
Deep Foundation Types
The 5 Types of Deep Foundations
- Basements.
- Buoyancy rafts.
- Caissons.
- Shaft foundations.
- Pile foundations.
Helical Pile Installation
Helical piles are created by first digging far into the ground. The deeper the hole, the more weight the building space will be able to support. Construction technicians then create multiple piles that build into one large platform, which is designed to support the building to be installed atop of the foundation.
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