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Type of foundation

Drilling of deep piles of diameter 150cm in bridge 423 near Nes Ziona, Israel

A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the footing at the building site.

There are many reasons that a geotechnical engineer would recommend a deep foundation over a shallow foundation, such as for a skyscraper. Some of the common reasons are very large design loads, a poor soil at shallow depth, or site constraints similar property lines. At that place are dissimilar terms used to depict dissimilar types of deep foundations including the pile (which is analogous to a pole), the pier (which is analogous to a column), drilled shafts, and caissons. Piles are generally driven into the basis in situ; other deep foundations are typically put in place using excavation and drilling. The naming conventions may vary between engineering disciplines and firms. Deep foundations tin be made out of timber, steel, reinforced concrete or prestressed physical.

Driven foundations [edit]

Piping piles being driven into the basis

Illustration of a hand-operated pile commuter in Deutschland after 1480

Prefabricated piles are driven into the ground using a pile driver. Driven piles are synthetic of wood, reinforced concrete, or steel. Wooden piles are fabricated from the trunks of tall trees. Concrete piles are available in foursquare, octagonal, and round cantankerous-sections (like Franki piles). They are reinforced with rebar and are often prestressed. Steel piles are either pipe piles or some sort of beam section (like an H-pile). Historically, forest piles used splices to join multiple segments end-to-end when the driven depth required was too long for a single pile; today, splicing is common with steel piles, though concrete piles can be spliced with mechanical and other means. Driving piles, as opposed to drilling shafts, is advantageous because the soil displaced by driving the piles compresses the surrounding soil, causing greater friction against the sides of the piles, thus increasing their load-bearing capacity. Driven piles are likewise considered to be "tested" for weight-bearing ability because of their method of installation; thus the motto of the Pile Driving Contractors' Association is "A Driven Pile...Is a Tested Pile!".^[1]

Pile foundation systems [edit]

Foundations relying on driven piles frequently have groups of piles continued by a pile cap (a large concrete block into which the heads of the piles are embedded) to distribute loads that are greater than ane pile can bear. Pile caps and isolated piles are typically connected with form beams to tie the foundation elements together; lighter structural elements touch the grade beams, while heavier elements bear directly on the pile cap.^{[ citation needed ]}

Monopile foundation [edit]

A monopile foundation utilizes a unmarried, more often than not large-diameter, foundation structural element to support all the loads (weight, wind, etc.) of a big above-surface structure.

A big number of monopile foundations^[ii] take been utilized in recent years for economically constructing fixed-bottom offshore current of air farms in shallow-water subsea locations.^[3] For example, the Horns Rev current of air farm in the Northward Sea westward of Denmark utilizes 80 large monopiles of 4 metres diameter sunk 25 meters deep into the seabed,^[iv] while the Lynn and Inner Dowsing Wind Subcontract off the coast of England went online in 2008 with over 100 turbines, each mounted on a 4.7-metre-diameter monopile foundation in bounding main depths up to 18 metres.^[5]

The typical construction process for a wind turbine subsea monopile foundation in sand includes driving a big hollow steel pile, of some 4 m in diameter with approximately 50mm thick walls, some 25 m deep into the seabed, through a 0.5 1000 layer of larger stone and gravel to minimize erosion around the pile. A transition slice (consummate with pre-installed features such as gunkhole-landing arrangement, cathodic protection, cablevision ducts for sub-marine cables, turbine tower flange, etc.) is attached to the driven pile, and the sand and h2o are removed from the centre of the pile and replaced with concrete. An additional layer of fifty-fifty larger stone, up to 0.5 m diameter, is applied to the surface of the seabed for longer-term erosion protection.^[3]

Drilled piles [edit]

Too chosen caissons, drilled shafts, drilled piers, cast-in-drilled-hole piles (CIDH piles) or cast-in-situ piles, a borehole is drilled into the ground, then concrete (and often some sort of reinforcing) is placed into the borehole to form the pile. Rotary irksome techniques allow larger diameter piles than whatsoever other piling method and let pile structure through particularly dumbo or hard strata. Construction methods depend on the geology of the site; in particular, whether boring is to be undertaken in 'dry out' ground conditions or through water-saturated strata. Casing is often used when the sides of the borehole are probable to slough off before concrete is poured.

For finish-begetting piles, drilling continues until the borehole has extended a sufficient depth (socketing) into a sufficiently strong layer. Depending on site geology, this tin can exist a rock layer, or hardpan, or other dense, strong layers. Both the diameter of the pile and the depth of the pile are highly specific to the ground atmospheric condition, loading conditions, and nature of the project. Pile depths may vary substantially across a projection if the begetting layer is not level. Drilled piles can be tested using a diversity of methods to verify the pile integrity during installation.

Under-reamed piles [edit]

Under-reamed piles have mechanically formed enlarged bases that are as much as 6 m in bore.^{[ citation needed ]} The course is that of an inverted cone and can only be formed in stable soils. The larger base diameter allows greater bearing chapters than a straight-shaft pile.

These piles are suited for expansive soils which are often subjected to seasonal moisture variations, or for loose or soft strata. They are used in normal ground condition also where economic science are favorable. ^[six] ^{[ total citation needed ]}

Under reamed piles foundation is used for the following soils:-

1. Under reamed piles are used in black cotton wool soil: This type of soil expands when information technology comes in contact with water and wrinkle occurs when h2o is removed. Then that cracks announced in the structure done on such clay. An under reamed pile is used in the base to remove this defect.

2. Under reamed piles are used in depression bearing capacity Outdated soil (filled soil)

3.Under reamed piles are used in sandy soil when water table is loftier.

4. Under reamed piles are used, Where lifting forces appear at the base of operations of foundation.

Augercast pile [edit]

An augercast pile, oftentimes known as a continuous flying augering (CFA) pile, is formed by drilling into the ground with a hollow stemmed continuous flight auger to the required depth or degree of resistance. No casing is required. A cement grout mix is then pumped downwards the stem of the auger. While the cement grout is pumped, the auger is slowly withdrawn, carrying the soil upward along the flights. A shaft of fluid cement grout is formed to footing level. Reinforcement can be installed. Recent innovations in addition to stringent quality control allows reinforcing cages to be placed up to the total length of a pile when required.^{[ citation needed ]}

Augercast piles crusade minimal disturbance and are often used for dissonance-sensitive and environmentally-sensitive sites. Augercast piles are not more often than not suited for utilise in contaminated soils, because of expensive waste matter disposal costs. In cases such every bit these, a displacement pile (like Olivier piles) may provide the price efficiency of an augercast pile and minimal environmental impact. In basis containing obstructions or cobbles and boulders, augercast piles are less suitable as refusal above the pattern pile tip elevation may be encountered.^{[ citation needed ]}

Pier and grade axle foundation [edit]

In drilled pier foundations, the piers tin be connected with grade beams on which the structure sits, sometimes with heavy cavalcade loads begetting straight on the piers. In some residential structure, the piers are extended above the ground level, and wood beams bearing on the piers are used to support the construction. This type of foundation results in a clamber space underneath the building in which wiring and duct piece of work can be laid during construction or re-modelling.^[7]

Speciality piles [edit]

Jet-piles [edit]

In jet piling high pressure water is used to set piles.^[8] High pressure h2o cuts through soil with a high-pressure jet flow and allows the pile to exist fitted.^[9] One advantage of Jet Piling: the h2o jet lubricates the pile and softens the basis.^[10] The method is in employ in Norway.^[11]

Micropiles [edit]

Micropiles are small diameter, generally less than 300mm diameter, elements that are drilled and grouted in place. They typically become their capacity from skin friction along the sides of the element, just tin can be finish bearing in hard rock equally well. Micropiles are commonly heavily reinforced with steel comprising more than 40% of their cross section. They tin can be used equally straight structural support or as ground reinforcement elements. Due to their relatively high cost and the blazon of equipment used to install these elements, they are ofttimes used were access restrictions and or very difficult ground conditions (cobbles and boulders, structure debris, karst, environmental sensitivity) exists or to retrofit existing structures. Occasionally, in difficult ground, they are used for new structure foundation elements. Typical applications include underpinning, span, manual tower and slope stabilization projects.^[12] ^[xiii] ^[14] ^[xv]

Tripod piles [edit]

The use of a tripod rig to install piles is 1 of the more traditional ways of forming piles. Although unit of measurement costs are mostly higher than with most other forms of piling,^{[ commendation needed ]} it has several advantages which take ensured its continued use through to the present twenty-four hours. The tripod system is easy and inexpensive to bring to site, making information technology ideal for jobs with a minor number of piles.

Sheet piles [edit]

Sheet piles are used to restrain soft soil above the bedrock in this digging

Sheet piling is a grade of driven piling using sparse interlocking sheets of steel to obtain a continuous bulwark in the ground. The main application of canvas piles is in retaining walls and cofferdams erected to enable permanent works to go along. Ordinarily, vibrating hammer, t-crane and crawle drilling are used to establish sheet piles.^{[ citation needed ]}

Soldier piles [edit]

A soldier pile wall using reclaimed railway sleepers as lagging.

Soldier piles, as well known as king piles or Berlin walls, are synthetic of wide flange steel H sections spaced about 2 to 3 m autonomously and are driven prior to earthworks. As the excavation proceeds, horizontal timber sheeting (lagging) is inserted behind the H pile flanges.

The horizontal earth pressures are concentrated on the soldier piles because of their relative rigidity compared to the lagging. Soil movement and subsidence is minimized past maintaining the lagging in house contact with the soil.^{[ commendation needed ]}

Soldier piles are about suitable in atmospheric condition where well constructed walls volition not effect in subsidence such as over-consolidated clays, soils above the h2o table if they have some cohesion, and complimentary draining soils which can be effectively dewatered, like sands.^{[ citation needed ]}

Unsuitable soils include soft clays and weak running soils that permit large movements such as loose sands. It is also non possible to extend the wall beyond the bottom of the excavation, and dewatering is often required.^{[ commendation needed ]}

Screw piles [edit]

Screw piles, also called helical piers and screw foundations, accept been used as foundations since the mid 19th century in screw-pile lighthouses.^{[ citation needed ]} Spiral piles are galvanized iron pipage with helical fins that are turned into the footing by machines to the required depth. The spiral distributes the load to the soil and is sized accordingly.

Suction piles [edit]

Suction piles are used underwater to secure floating platforms. Tubular piles are driven into the seabed (or more than unremarkably dropped a few metres into a soft seabed) so a pump sucks water out at the top of the tubular, pulling the pile farther down.

The proportions of the pile (diameter to height) are dependent upon the soil blazon. Sand is difficult to penetrate but provides skillful holding capacity, so the pinnacle may be every bit short as half the diameter. Clays and muds are easy to penetrate but provide poor holding capacity, so the pinnacle may be as much as viii times the bore. The open nature of gravel ways that water would flow through the ground during installation, causing 'piping' catamenia (where water boils upwardly through weaker paths through the soil). Therefore, suction piles cannot exist used in gravel seabeds.^{[ citation needed ]}

Adfreeze piles [edit]

Adfreeze piles supporting a building in Utqiaġvik, Alaska

In high latitudes where the ground is continuously frozen, adfreeze piles are used as the chief structural foundation method.

Adfreeze piles derive their strength from the bond of the frozen ground around them to the surface of the pile.^{[ citation needed ]}

Adfreeze pile foundations are particularly sensitive in conditions which crusade the permafrost to melt. If a building is synthetic improperly then it can melt the ground below, resulting in a failure of the foundation system.^{[ citation needed ]}

Vibrated stone columns [edit]

Vibrated rock columns are a footing improvement technique where columns of fibroid aggregate are placed in soils with poor drainage or bearing chapters to improve the soils.^{[ citation needed ]}

Hospital piles [edit]

Specific to marine structures, hospital piles (also known as gallow piles) are built to provide temporary support to marine structure components during refurbishment works. For example, when removing a river pontoon, the brow will be fastened to hospital pile to support information technology. They are normal piles, usually with a chain or hook attachment.

Piled walls [edit]

These methods of retaining wall structure employ bored piling techniques, normally CFA or rotary. They provide special advantages where bachelor working infinite dictates that basement excavation faces be vertical. Both methods offer technically effective and offer a toll efficient temporary or permanent means of retaining the sides of bulk excavations even in h2o begetting strata. When used in permanent works, these walls tin be designed to conform vertical loads in improver to moments and horizontal forces. Structure of both methods is the aforementioned as for foundation bearing piles. Face-to-face walls are constructed with small gaps betwixt adjacent piles. The size of this space is adamant past the strength of the soils.

Secant piled walls [edit]

Secant pile walls are constructed such that space is left between alternating 'female' piles for the subsequent structure of 'male' piles.^{[ description needed ]} Construction of 'male' piles involves boring through the physical in the 'female' piles hole in order to key 'male' piles between. The male person pile is the 1 where steel reinforcement cages are installed, though in some cases the female piles are also reinforced.^{[ citation needed ]}

Secant piled walls tin can either exist true hard/hard, difficult/intermediate (house), or hard/soft, depending on design requirements. Hard refers to structural concrete and firm or soft is usually a weaker grout mix containing bentonite.^{[ citation needed ]} All types of wall tin be synthetic as free standing cantilevers, or may be propped if infinite and sub-structure design permit. Where political party wall agreements allow, ground anchors can exist used as tie backs.

Slurry walls [edit]

A slurry wall is a barrier built nether basis using a mix of bentonite and water to preclude the period of groundwater. A trench that would collapse due to the hydraulic force per unit area in the surrounding soil does not collapse as the slurry balances the hydraulic pressure.

Deep mixing/mass stabilization techniques [edit]

These are essentially variations of in situ reinforcements in the form of piles (as mentioned above), blocks or larger volumes.

Cement, lime/quick lime, flyash, sludge and/or other binders (sometimes called stabilizer) are mixed into the soil to increase begetting capacity. The effect is non equally solid as concrete, only should exist seen as an improvement of the bearing chapters of the original soil.

The technique is almost often applied on clays or organic soils like peat. The mixing can be carried out by pumping the binder into the soil whilst mixing information technology with a device normally mounted on an excavator or by excavating the masses, mixing them separately with the binders and refilling them in the desired area. The technique can as well be used on lightly contaminated masses equally a means of bounden contaminants, every bit opposed to excavating them and transporting to landfill or processing.

Materials [edit]

Timber [edit]

As the name implies, timber piles are made of woods.

Historically, timber has been a plentiful, locally bachelor resource in many areas. Today, timber piles are all the same more affordable than concrete or steel. Compared to other types of piles (steel or concrete), and depending on the source/blazon of timber, timber piles may not be suitable for heavier loads.

A main consideration regarding timber piles is that they should be protected from rotting above groundwater level. Timber will last for a long time below the groundwater level. For timber to rot, ii elements are needed: h2o and oxygen. Below the groundwater level, dissolved oxygen is lacking even though at that place is aplenty h2o. Hence, timber tends to last for a long time below the groundwater level. In 1648, the Royal Palace of Amsterdam was constructed on 13,659 timber piles that still survive today since they were below groundwater level. Timber that is to be used above the water table can be protected from decay and insects past numerous forms of wood preservation using pressure treatment (element of group i copper 4th (ACQ), chromated copper arsenate (CCA), creosote, etc.).

Splicing timber piles is still quite common and is the easiest of all the piling materials to splice. The normal method for splicing is by driving the leader pile first, driving a steel tube (usually 60–100 cm long, with an internal diameter no smaller than the minimum toe diameter) one-half its length onto the end of the leader pile. The follower pile is so simply slotted into the other stop of the tube and driving continues. The steel tube is simply there to ensure that the 2 pieces follow each other during driving. If uplift capacity is required, the splice can incorporate bolts, coach screws, spikes or the similar to give it the necessary capacity.

Atomic number 26 [edit]

Iron may be used for piling. These may be ductile.^{[ citation needed ]}

Steel [edit]

Cutaway analogy. Deep inclined (dilapidated) pipage piles support a precast segmented skyway where upper soil layers are weak muds.

Pipe piles are a type of steel driven pile foundation and are a good candidate for inclined (battered) piles.

Pipage piles can be driven either open terminate or airtight terminate. When driven open end, soil is immune to enter the bottom of the pipe or tube. If an empty pipage is required, a jet of h2o or an auger can be used to remove the soil inside following driving. Airtight end pipe piles are constructed by covering the bottom of the pile with a steel plate or cast steel shoe.

In some cases, pipe piles are filled with concrete to provide additional moment capacity or corrosion resistance. In the United Kingdom, this is by and large non done in order to reduce the price. In these cases corrosion protection is provided by allowing for a sacrificial thickness of steel or by adopting a college grade of steel. If a concrete filled pipe pile is corroded, most of the load carrying chapters of the pile will remain intact due to the concrete, while it will exist lost in an empty pipe pile. The structural chapters of pipe piles is primarily calculated based on steel strength and physical forcefulness (if filled). An allowance is made for corrosion depending on the site atmospheric condition and local building codes. Steel pipe piles tin can either be new steel manufactured specifically for the piling industry or reclaimed steel tubular casing previously used for other purposes such every bit oil and gas exploration.

H-Piles are structural beams that are driven in the ground for deep foundation application. They tin be easily cut off or joined by welding or mechanical drive-fit splicers. If the pile is driven into a soil with low pH value, then there is a risk of corrosion, coal-tar epoxy or cathodic protection can exist applied to dull or eliminate the corrosion procedure. Information technology is common to allow for an amount of corrosion in design by simply over dimensioning the cross-exclusive surface area of the steel pile. In this mode, the corrosion process can be prolonged up to 50 years.

Prestressed physical piles [edit]

Concrete piles are typically made with steel reinforcing and prestressing tendons to obtain the tensile forcefulness required, to survive handling and driving, and to provide sufficient bending resistance.

Long piles can exist hard to handle and transport. Pile joints tin be used to join two or more brusk piles to form one long pile. Pile joints can exist used with both precast and prestressed physical piles.

Composite piles [edit]

A "composite pile" is a pile made of steel and concrete members that are fastened together, end to end, to grade a unmarried pile. It is a combination of different materials or unlike shaped materials such as pipe and H-beams or steel and concrete.

'Pile jackets' encasing old physical piles in a saltwater surround to forbid corrosion and consequential weakening of the piles when cracks allow saltwater to contact the internal steel reinforcement rods

Notes [edit]

^ PDCA
^ Offshore Wind Turbine Foundations, 2009-09-09, accessed 2010-04-12.
^ ^a ^b Constructing a turbine foundation Archived 21 May 2022 at the Wayback Car Horns Rev project, Elsam monopile foundation construction process, accessed 2010-04-12]
^ Horns Revolution Archived 14 July 2022 at the Wayback Machine, Modern Power Systems, 2002-10-05, accessed 2010-04-14.
^ "Lynn and Inner Dowsing description". Archived from the original on 26 July 2022. Retrieved 23 July 2010.
^ Handbook on Under-reamed and bored compaction pile foundation, Central building research institute Roorkee, Prepared by Devendra Sharma, 1000. P. Jain, Chandra Prakash
^ Marshall, Brain (April 2000). "How House Construction Works". How Stuff Works. HowStuffWorks, Inc. Retrieved four April 2022.
^ "jet-pile". Merriam-webster.com. Merriam-Webster, Inc. Retrieved 2 August 2022.
^ Guan, Chengli; Yang, Yuyou (21 February 2022). "Field Report on the Waterstop of the Rodin Jet Pile". Applied Sciences. doi:x.3390/app9081709 . Retrieved 2 Baronial 2022.
^ "Printing-in with Water Jetting". Giken.com. Giken Ltd. Retrieved 2 August 2022.
^ "Metropolis Lade, Trondheim". Jetgrunn.no. Jetgrunn AS. Retrieved 2 Baronial 2022.
^ Siel, Barry D.; Anderson, Scott A. "Implementation Of Micropiles By The Federal Highway Assistants" (PDF). Federal Highway Administration (U.s.).
^ Omer, Joshua R. (2010). "A Numerical Model for Load Transfer and Settlement of Bored Bandage In-Situ Piles". Proceedings of the 35th Annual Conference on Deep Foundations.
^ "International Lodge for Micropiles". Retrieved 2 February 2007.
^ "Login | GeoTechTools | Geo-Plant". www.geoinstitute.org . Retrieved 15 April 2022.

References [edit]

Italiantrivelle Foundation Industry The Deep Foundation web portal Italiantrivelle is the number one source of information regarding the Foundation Industry. (Link needs to be removed or updated, links to inappropriate content)
Fleming, Westward. Chiliad. 1000. et al., 1985, Piling Engineering, Surrey University Press; Hunt, R. East., Geotechnical Technology Analysis and Evaluation, 1986, McGraw-Hill.
Coduto, Donald P. Foundation Design: Principles and Practices 2nd ed., Prentice-Hall Inc., 2001.
NAVFAC DM seven.02 Foundations and World Structures U.S. Naval Facilities Engineering Command, 1986.
Rajapakse, Ruwan., Pile Blueprint and Construction Guide, 2003
Tomlinson, P.J., Pile Design and Construction Practice, 1984
Stabilization of Organic Soils
Canvas piling handbook, 2010

External links [edit]

Deep Foundations Institute
PDCA: Pile Driving Contractors' Clan
ADSC: The International Association of Foundation Drilling
International Lodge for Micropiles
Federation of Piling Specialists (Uk)
Process of Installing Drilled Shaft (Bored Pile)