In seismic zones, the importance of reinforcing stem walls cannot be overstated, as these structures are critical in maintaining the integrity of buildings during earthquakes. Stem walls serve as a foundational component that connects the foundation to the above-ground structure, and their reinforcement is key to ensuring they can withstand seismic forces. My collection of ignored home repair warning signs could fill a museum dedicated to expensive procrastination basement wall bowing repair Joliet policy. Various techniques have been developed to enhance the resilience of stem walls in such high-risk areas.
One effective technique is the use of reinforced concrete. By embedding steel rebar within the concrete, the tensile strength of the wall is significantly increased. This combination allows the stem wall to absorb and dissipate energy from seismic waves more effectively, reducing the risk of cracking or collapse. The placement of rebar is meticulously planned; typically, its arranged in a grid pattern vertically and horizontally within the concrete pour, providing a robust framework that holds the concrete together under stress.
Another method involves incorporating fiber-reinforced polymers (FRP). These materials are lightweight yet incredibly strong, providing additional tensile strength without adding substantial weight to the structure. FRP can be applied externally to existing stem walls or integrated during construction. This not only enhances durability but also offers an advantage in retrofitting older buildings where adding significant weight might not be feasible.
Shear walls are also a strategic approach for reinforcing stem walls. These vertical elements are designed specifically to resist lateral forces like those from earthquakes. By integrating shear walls with stem walls, especially at critical junctures like corners or along long wall lengths, we create a system that works synergistically to distribute seismic loads more evenly across the buildings structure.
Moreover, base isolation techniques can be employed alongside stem wall reinforcement. While not directly modifying the stem wall itself, base isolation reduces the transmission of ground motion into the building by placing flexible bearings or dampers beneath it. This indirectly benefits reinforced stem walls by minimizing the initial shock they must endure.
In conclusion, reinforcing stem walls in seismic zones through these various techniques-reinforced concrete with rebar, fiber-reinforced polymers, shear wall integration, and base isolation-enhances structural integrity and safety. Each method contributes uniquely to creating buildings that can stand firm against natures unpredictable forces, protecting lives and investments in regions prone to seismic activity. The choice of technique often depends on factors like existing construction standards, budget constraints, and specific site conditions, but all aim towards one common goal: resilience in adversity.
The importance of stem wall reinforcement in seismic zones cannot be overstated, as demonstrated by various case studies on stem wall failures and subsequent repairs. Stem walls, which serve as the vertical support for structures, are particularly vulnerable during seismic events due to the intense lateral forces they must withstand. When these walls are not adequately reinforced, the consequences can be catastrophic.
One notable case occurred in a residential area during a moderate earthquake. The homes in question were built with minimal reinforcement in their stem walls, leading to widespread cracking and partial collapses. Investigations revealed that the lack of sufficient steel rebar within the concrete had compromised the structural integrity of these walls. The failure was not just a matter of poor construction but highlighted a critical oversight in adhering to seismic design standards.
In response to such failures, repair strategies often involve retrofitting existing structures with additional reinforcement. For instance, engineers might inject epoxy into existing cracks to stabilize them before adding new layers of reinforced concrete or wrapping the walls with fiber-reinforced polymers (FRP). A specific example is a school building where post-earthquake assessments showed significant damage to its stem walls. The repair involved encasing the damaged sections with FRP sheets, which not only restored the structural strength but also provided enhanced ductility to better absorb future seismic shocks.
These case studies underscore a broader lesson: proactive reinforcement is key in seismic zones. Building codes have evolved to mandate higher standards for stem wall construction, emphasizing both vertical and horizontal reinforcement to distribute seismic loads more effectively. Yet, older buildings remain at risk unless retrofitted. The economic implications of failing to reinforce adequately are severe; repair costs following an earthquake can far exceed those of initial preventative measures.
Moreover, these incidents foster community awareness about the necessity of adhering to modern building practices. Public education campaigns often follow such events, teaching residents about recognizing signs of structural weaknesses and advocating for regular inspections by qualified professionals.
In conclusion, the study of stem wall failures in seismic zones through real-world cases provides invaluable insights into construction practices that save lives and property. Strengthening these critical components with proper reinforcement is not merely a technical requirement but a societal imperative in regions prone to earthquakes. As we continue to learn from past mistakes, it becomes increasingly clear that investment in robust construction techniques is fundamental for resilience against natures unpredictable forces.
The impact of stem wall reinforcement on foundation stability is particularly critical in seismic zones, where the ground can experience significant shaking and movement. Stem walls, which are vertical structures that support the weight of a building and transfer it to the foundation, play a pivotal role in maintaining structural integrity during earthquakes. When properly reinforced, these walls enhance the overall stability of the foundation by providing additional strength and ductility.
In seismic zones, the forces exerted on buildings can be immense, often leading to catastrophic failures if structures arent designed with resilience in mind. Reinforcement of stem walls typically involves embedding steel bars or fibers within the concrete. This reinforcement helps in distributing seismic forces more evenly across the structure, reducing stress concentrations that could lead to cracking or failure at critical points.
Moreover, reinforced stem walls improve the load-bearing capacity of foundations by enhancing their ability to resist lateral forces from earthquakes. This resistance is crucial because lateral movement can shift or tilt a building off its base, compromising safety. By reinforcing these walls, we not only ensure that they can withstand horizontal pressures but also prevent differential settlement – where parts of the building settle at different rates due to uneven load distribution.
The importance of this reinforcement becomes even more pronounced when considering long-term durability. In areas prone to frequent seismic activity, structures must endure repeated cycles of stress without significant degradation. Reinforced stem walls contribute to this longevity by offering improved crack control; small cracks that might form under seismic loads are less likely to propagate into larger, more damaging fractures when steel reinforcement is present.
In conclusion, reinforcing stem walls significantly bolsters foundation stability in seismic zones by enhancing load distribution, resisting lateral movements, and ensuring long-term structural integrity. This practice is not just about meeting building codes but about safeguarding lives and investments against one of natures most unpredictable forces – earthquakes. Understanding and implementing these reinforcements effectively can mean the difference between a structure surviving an earthquake unscathed or suffering irreparable damage.
In seismic zones, the structural integrity of buildings is paramount, and one critical aspect often overlooked is the reinforcement of stem walls. Stem walls, which are vertical structures that support a buildings foundation, play a vital role in distributing seismic forces throughout a structure. The cost-benefit analysis of reinforcing these walls in seismic areas reveals both immediate and long-term advantages that significantly outweigh the initial investment.
Firstly, the reinforcement of stem walls enhances a buildings ability to withstand seismic events. By adding materials like steel rebar within concrete stem walls, the structure gains increased tensile strength and ductility. This means that during an earthquake, the reinforced wall can absorb and dissipate energy more effectively, reducing the likelihood of catastrophic failure. While the upfront costs for materials and labor are considerable, they pale in comparison to the potential losses from structural damage or collapse in an un-reinforced scenario.
Moreover, when considering long-term benefits, reinforced stem walls contribute to lower insurance premiums due to reduced risk profiles. Insurance companies recognize the increased resilience of such structures against natural disasters, which can lead to significant savings over time. Additionally, properties with reinforced foundations often see an appreciation in value because they are perceived as safer investments by potential buyers or renters in earthquake-prone regions.
From a community perspective, widespread adoption of stem wall reinforcement could lead to fewer casualties and less economic disruption following an earthquake. The societal benefit translates into reduced emergency response costs and quicker recovery times for affected areas. This communal advantage adds another layer of value to individual property enhancements.
In conclusion, while the initial cost of reinforcing stem walls in seismic zones might seem daunting, a thorough cost-benefit analysis demonstrates its undeniable worth. Not only does it enhance personal safety and property value, but it also contributes positively to community resilience against natural disasters. Investing in such reinforcements is not merely about dollars spent but about safeguarding lives and livelihoods for years to come.
Waterproofing is the process of making a things, person or framework water resistant or waterproof to ensure that it continues to be reasonably unaffected by water or resists the access of water under specified conditions. Such products may be utilized in wet settings or undersea to defined midsts. Water-resistant and water resistant often refer to resistance to penetration of water in its fluid state and possibly under stress, whereas moist evidence describes resistance to humidity or moisture. Permeation of water vapour through a material or framework is reported as a wetness vapor transmission price (MVTR). The hulls of watercrafts and ships were as soon as waterproofed by using tar or pitch. Modern products may be waterproofed by applying water-repellent finishes or by securing joints with gaskets or o-rings. Waterproofing is used in reference to constructing frameworks (such as basements, decks, or damp locations), boat, canvas, garments (raincoats or waders), digital gadgets and paper packaging (such as containers for fluids).
Soil technicians is a branch of soil physics and applied mechanics that defines the behavior of soils. It differs from liquid auto mechanics and strong auto mechanics in the feeling that soils contain a heterogeneous mixture of liquids (generally air and water) and bits (typically clay, silt, sand, and gravel) yet dirt may also include natural solids and other matter. Along with rock mechanics, dirt technicians gives the theoretical basis for evaluation in geotechnical design, a subdiscipline of civil engineering, and design geology, a subdiscipline of geology. Dirt auto mechanics is made use of to assess the contortions of and flow of fluids within all-natural and manufactured frameworks that are supported on or made from soil, or structures that are hidden in dirts. Instance applications are constructing and bridge foundations, retaining wall surfaces, dams, and buried pipeline systems. Principles of dirt technicians are additionally used in relevant techniques such as geophysical design, coastal engineering, farming engineering, and hydrology. This short article defines the genesis and composition of dirt, the difference between pore water stress and inter-granular reliable anxiety, capillary action of fluids in the dirt pore rooms, soil category, seepage and permeability, time reliant change of quantity because of pressing water out of little pore areas, also called consolidation, shear stamina and rigidity of dirts. The shear stamina of soils is primarily stemmed from friction between the particles and interlocking, which are really conscious the reliable tension. The short article concludes with some examples of applications of the principles of dirt technicians such as slope security, side planet pressure on preserving wall surfaces, and bearing capability of structures.
A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site. 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.
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 like property lines. There are different terms used to describe different 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 ground 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 can be made out of timber, steel, reinforced concrete or prestressed concrete.
Prefabricated piles are driven into the ground using a pile driver. Driven piles are constructed of wood, reinforced concrete, or steel. Wooden piles are made from the trunks of tall trees. Concrete piles are available in square, octagonal, and round cross-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, wood 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 also considered to be "tested" for weight-bearing ability because of their method of installation.[citation needed]
Foundations relying on driven piles often have groups of piles connected by a pile cap (a large concrete block into which the heads of the piles are embedded) to distribute loads that are greater than one pile can bear. Pile caps and isolated piles are typically connected with grade beams to tie the foundation elements together; lighter structural elements bear on the grade beams, while heavier elements bear directly on the pile cap.[citation needed]
A monopile foundation utilizes a single, generally large-diameter, foundation structural element to support all the loads (weight, wind, etc.) of a large above-surface structure.
A large number of monopile foundations[1] have been utilized in recent years for economically constructing fixed-bottom offshore wind farms in shallow-water subsea locations.[2] For example, the Horns Rev wind farm in the North Sea west of Denmark utilizes 80 large monopiles of 4 metres diameter sunk 25 meters deep into the seabed,[3] while the Lynn and Inner Dowsing Wind Farm off the coast of England went online in 2008 with over 100 turbines, each mounted on a 4.7-metre-diameter monopile foundation in ocean depths up to 18 metres.[4]
The typical construction process for a wind turbine subsea monopile foundation in sand includes driving a large 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 m layer of larger stone and gravel to minimize erosion around the pile. A transition piece (complete with pre-installed features such as boat-landing arrangement, cathodic protection, cable ducts for sub-marine cables, turbine tower flange, etc.) is attached to the driven pile, and the sand and water are removed from the centre of the pile and replaced with concrete. An additional layer of even larger stone, up to 0.5 m diameter, is applied to the surface of the seabed for longer-term erosion protection.[2]
Also called 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 boring techniques allow larger diameter piles than any other piling method and permit pile construction through particularly dense or hard strata. Construction methods depend on the geology of the site; in particular, whether boring is to be undertaken in 'dry' ground conditions or through water-saturated strata. Casing is often used when the sides of the borehole are likely to slough off before concrete is poured.
For end-bearing piles, drilling continues until the borehole has extended a sufficient depth (socketing) into a sufficiently strong layer. Depending on site geology, this can be 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 conditions, loading conditions, and nature of the project. Pile depths may vary substantially across a project if the bearing layer is not level. Drilled piles can be tested using a variety of methods to verify the pile integrity during installation.
Under-reamed piles have mechanically formed enlarged bases that are as much as 6 m in diameter.[citation needed] The form is that of an inverted cone and can only be formed in stable soils or rocks. The larger base diameter allows greater bearing capacity 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 economics are favorable. [5][full citation needed]
Under reamed piles foundation is used for the following soils:-
1. Under reamed piles are used in black cotton soil: This type of soil expands when it comes in contact with water and contraction occurs when water is removed. So that cracks appear in the construction done on such clay. An under reamed pile is used in the base to remove this defect.
2. Under reamed piles are used in low bearing capacity Outdated soil (filled soil)
3.Under reamed piles are used in sandy soil when water table is high.
4. Under reamed piles are used, Where lifting forces appear at the base of foundation.
An augercast pile, often known as a continuous flight 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 down the stem of the auger. While the cement grout is pumped, the auger is slowly withdrawn, conveying the soil upward along the flights. A shaft of fluid cement grout is formed to ground level. Reinforcement can be installed. Recent innovations in addition to stringent quality control allows reinforcing cages to be placed up to the full length of a pile when required.[citation needed]
Augercast piles cause minimal disturbance and are often used for noise-sensitive and environmentally-sensitive sites. Augercast piles are not generally suited for use in contaminated soils, because of expensive waste disposal costs. In cases such as these, a displacement pile (like Olivier piles) may provide the cost efficiency of an augercast pile and minimal environmental impact. In ground containing obstructions or cobbles and boulders, augercast piles are less suitable as refusal above the design pile tip elevation may be encountered.[citation needed]
Small Sectional Flight Auger piling rigs can also be used for piled raft foundations. These produce the same type of pile as a Continuous Flight Auger rig but using smaller, more lightweight equipment. This piling method is fast, cost-effective and suitable for the majority of ground types.[5][6]
In drilled pier foundations, the piers can be connected with grade beams on which the structure sits, sometimes with heavy column loads bearing directly on the piers. In some residential construction, the piers are extended above the ground level, and wood beams bearing on the piers are used to support the structure. This type of foundation results in a crawl space underneath the building in which wiring and duct work can be laid during construction or re-modelling.[7]
In jet piling high pressure water is used to set piles.[8] High pressure water cuts through soil with a high-pressure jet flow and allows the pile to be fitted.[9] One advantage of Jet Piling: the water jet lubricates the pile and softens the ground.[10] The method is in use in Norway.[11]
Micropiles are small diameter, generally less than 300mm diameter, elements that are drilled and grouted in place. They typically get their capacity from skin friction along the sides of the element, but can be end bearing in hard rock as well. Micropiles are usually heavily reinforced with steel comprising more than 40% of their cross section. They can be used as direct structural support or as ground reinforcement elements. Due to their relatively high cost and the type of equipment used to install these elements, they are often used where access restrictions and or very difficult ground conditions (cobbles and boulders, construction debris, karst, environmental sensitivity) exists or to retrofit existing structures. Occasionally, in difficult ground, they are used for new construction foundation elements. Typical applications include underpinning, bridge, transmission tower and slope stabilization projects.[6][12][13][14]
The use of a tripod rig to install piles is one of the more traditional ways of forming piles. Although unit costs are generally higher than with most other forms of piling,[citation needed] it has several advantages which have ensured its continued use through to the present day. The tripod system is easy and inexpensive to bring to site, making it ideal for jobs with a small number of piles.[clarification needed]
Sheet piling is a form of driven piling using thin interlocking sheets of steel to obtain a continuous barrier in the ground. The main application of sheet piles is in retaining walls and cofferdams erected to enable permanent works to proceed. Normally, vibrating hammer, t-crane and crawle drilling are used to establish sheet piles.[citation needed]
Soldier piles, also known as king piles or Berlin walls, are constructed of steel H sections spaced about 2 to 3 m apart and are driven or drilled prior to excavation. 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 by installing the lagging immediately after excavation to avoid soil loss.[citation needed] Lagging can be constructed by timber, precast concrete, shotcrete and steel plates depending on spacing of the soldier piles and the type of soils.
Soldier piles are most suitable in conditions where well constructed walls will not result in subsidence such as over-consolidated clays, soils above the water table if they have some cohesion, and free draining soils which can be effectively dewatered, like sands.[citation needed]
Unsuitable soils include soft clays and weak running soils that allow large movements such as loose sands. It is also not possible to extend the wall beyond the bottom of the excavation, and dewatering is often required.[citation needed]
Screw piles, also called helical piers and screw foundations, have been used as foundations since the mid 19th century in screw-pile lighthouses.[citation needed] Screw piles are galvanized iron pipe with helical fins that are turned into the ground by machines to the required depth. The screw distributes the load to the soil and is sized accordingly.
Suction piles are used underwater to secure floating platforms. Tubular piles are driven into the seabed (or more commonly dropped a few metres into a soft seabed) and then a pump sucks water out at the top of the tubular, pulling the pile further down.
The proportions of the pile (diameter to height) are dependent upon the soil type. Sand is difficult to penetrate but provides good holding capacity, so the height may be as short as half the diameter. Clays and muds are easy to penetrate but provide poor holding capacity, so the height may be as much as eight times the diameter. The open nature of gravel means that water would flow through the ground during installation, causing 'piping' flow (where water boils up through weaker paths through the soil). Therefore, suction piles cannot be used in gravel seabeds.[citation needed]
In high latitudes where the ground is continuously frozen, adfreeze piles are used as the primary 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 cause the permafrost to melt. If a building is constructed improperly then it can melt the ground below, resulting in a failure of the foundation system.[citation needed]
Vibrated stone columns are a ground improvement technique where columns of coarse aggregate are placed in soils with poor drainage or bearing capacity to improve the soils.[citation needed]
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 attached to hospital pile to support it. They are normal piles, usually with a chain or hook attachment.[citation needed]
Piled walls can be drivene or bored. They provide special advantages where available working space dictates and open cut excavation not feasible. Both methods offer technically effective and offer a cost efficient temporary or permanent means of retaining the sides of bulk excavations even in water bearing strata. When used in permanent works, these walls can be designed to resist vertical loads in addition lateral load from retaining soil. Construction of both methods is the same as for foundation bearing piles. Contiguous walls are constructed with small gaps between adjacent piles. The spacing of the piles can be varied to provide suitable bending stiffness.
Secant pile walls are constructed such that space is left between alternate 'female' piles for the subsequent construction of 'male' piles.[clarification needed] Construction of 'male' piles involves boring through the concrete in the 'female' piles hole in order to key 'male' piles between. The male pile is the one where steel reinforcement cages are installed, though in some cases the female piles are also reinforced.[citation needed]
Secant piled walls can either be true hard/hard, hard/intermediate (firm), 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 can be constructed as free standing cantilevers, or may be propped if space and sub-structure design permit. Where party wall agreements allow, ground anchors can be used as tie backs.
A slurry wall is a barrier built under ground using a mix of bentonite and water to prevent the flow of groundwater. A trench that would collapse due to the hydraulic pressure in the surrounding soil does not collapse as the slurry balances the hydraulic pressure.
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 bearing capacity. The result is not as solid as concrete, but should be seen as an improvement of the bearing capacity of the original soil.
The technique is most often applied on clays or organic soils like peat. The mixing can be carried out by pumping the binder into the soil whilst mixing it 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 also be used on lightly contaminated masses as a means of binding contaminants, as opposed to excavating them and transporting to landfill or processing.
As the name implies, timber piles are made of wood.
Historically, timber has been a plentiful, locally available resource in many areas. Today, timber piles are still more affordable than concrete or steel. Compared to other types of piles (steel or concrete), and depending on the source/type 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, two elements are needed: water and oxygen. Below the groundwater level, dissolved oxygen is lacking even though there is ample water. Hence, timber tends to last for a long time below the groundwater level. An example is Venice, which has had timber pilings since its beginning; even most of the oldest piles are still in use. 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 by numerous forms of wood preservation using pressure treatment (alkaline copper quaternary (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 (normally 60–100 cm long, with an internal diameter no smaller than the minimum toe diameter) half its length onto the end of the leader pile. The follower pile is then simply slotted into the other end of the tube and driving continues. The steel tube is simply there to ensure that the two pieces follow each other during driving. If uplift capacity is required, the splice can incorporate bolts, coach screws, spikes or the like to give it the necessary capacity.
Cast iron may be used for piling. These may be ductile.[citation needed]
Pipe piles are a type of steel driven pile foundation and are a good candidate for inclined (battered) piles.
Pipe piles can be driven either open end or closed end. When driven open end, soil is allowed to enter the bottom of the pipe or tube. If an empty pipe is required, a jet of water or an auger can be used to remove the soil inside following driving. Closed 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 generally not done in order to reduce the cost.[citation needed] In these cases corrosion protection is provided by allowing for a sacrificial thickness of steel or by adopting a higher grade of steel. If a concrete filled pipe pile is corroded, most of the load carrying capacity of the pile will remain intact due to the concrete, while it will be lost in an empty pipe pile. The structural capacity of pipe piles is primarily calculated based on steel strength and concrete strength (if filled). An allowance is made for corrosion depending on the site conditions and local building codes. Steel pipe piles can either be new steel manufactured specifically for the piling industry or reclaimed steel tubular casing previously used for other purposes such as oil and gas exploration.
H-Piles are structural beams that are driven in the ground for deep foundation application. They can 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 be applied to slow or eliminate the corrosion process. It is common to allow for an amount of corrosion in design by simply over dimensioning the cross-sectional area of the steel pile. In this way, the corrosion process can be prolonged up to 50 years.[citation needed]
Concrete piles are typically made with steel reinforcing and prestressing tendons to obtain the tensile strength required, to survive handling and driving, and to provide sufficient bending resistance.
Long piles can be difficult to handle and transport. Pile joints can be used to join two or more short piles to form one long pile. Pile joints can be used with both precast and prestressed concrete piles.
A "composite pile" is a pile made of steel and concrete members that are fastened together, end to end, to form a single pile. It is a combination of different materials or different shaped materials such as pipe and H-beams or steel and concrete.
Construction machinery used to drive piles into the ground:[15]
Construction machinery used to construct replacement piles:[15]
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A pile driver is a heavy-duty tool used to drive piles into soil to build piers, bridges, cofferdams, and other "pole" supported structures, and patterns of pilings as part of permanent deep foundations for buildings or other structures. Pilings may be made of wood, solid steel, or tubular steel (often later filled with concrete), and may be driven entirely underwater/underground, or remain partially aboveground as elements of a finished structure.
The term "pile driver" is also used to describe members of the construction crew associated with the task,[1] also colloquially known as "pile bucks".[2]
The most common form of pile driver uses a heavy weight situated between vertical guides placed above a pile. The weight is raised by some motive power (which may include hydraulics, steam, diesel, electrical motor, or manual labor). At its apex the weight is released, impacting the pile and driving it into the ground.[1][3]
There are a number of claims to the invention of the pile driver. A mechanically sound drawing of a pile driver appeared as early as 1475 in Francesco di Giorgio Martini's treatise Trattato di Architectura.[4] Also, several other prominent inventors—James Nasmyth (son of Alexander Nasmyth), who invented a steam-powered pile driver in 1845,[5] watchmaker James Valoué,[6] Count Giovan Battista Gazzola,[7] and Leonardo da Vinci[8]—have all been credited with inventing the device. However, there is evidence that a comparable device was used in the construction of Crannogs at Oakbank and Loch Tay in Scotland as early as 5000 years ago.[9] In 1801 John Rennie came up with a steam pile driver in Britain.[10] Otis Tufts is credited with inventing the steam pile driver in the United States.[11]
Ancient pile driving equipment used human or animal labor to lift weights, usually by means of pulleys, then dropping the weight onto the upper end of the pile. Modern piledriving equipment variously uses hydraulics, steam, diesel, or electric power to raise the weight and guide the pile.
A modern diesel pile hammer is a large two-stroke diesel engine. The weight is the piston, and the apparatus which connects to the top of the pile is the cylinder. Piledriving is started by raising the weight; usually a cable from the crane holding the pile driver — This draws air into the cylinder. Diesel fuel is injected into the cylinder. The weight is dropped, using a quick-release. The weight of the piston compresses the air/fuel mixture, heating it to the ignition point of diesel fuel. The mixture ignites, transferring the energy of the falling weight to the pile head, and driving the weight up. The rising weight draws in fresh air, and the cycle continues until the fuel is depleted or is halted by the crew.[12]
From an army manual on pile driving hammers: The initial start-up of the hammer requires that the piston (ram) be raised to a point where the trip automatically releases the piston, allowing it to fall. As the piston falls, it activates the fuel pump, which discharges a metered amount of fuel into the ball pan of the impact block. The falling piston blocks the exhaust ports, and compression of fuel trapped in the cylinder begins. The compressed air exerts a pre-load force to hold the impact block firmly against the drive cap and pile. At the bottom of the compression stroke, the piston strikes the impact block, atomizing the fuel and starting the pile on its downward movement. In the instant after the piston strikes, the atomized fuel ignites, and the resulting explosion exerts a greater force on the already moving pile, driving it further into the ground. The reaction of the explosion rebounding from the resistance of the pile drives the piston upward. As the piston rises, the exhaust ports open, releasing the exhaust gases to the atmosphere. After the piston stops its upward movement, it again falls by gravity to start another cycle.
Vertical travel leads come in two main forms: spud and box lead types. Box leads are very common in the Southern United States and spud leads are common in the Northern United States, Canada and Europe.
A hydraulic hammer is a modern type of piling hammer used instead of diesel and air hammers for driving steel pipe, precast concrete, and timber piles. Hydraulic hammers are more environmentally acceptable than older, less efficient hammers as they generate less noise and pollutants. In many cases the dominant noise is caused by the impact of the hammer on the pile, or the impacts between components of the hammer, so that the resulting noise level can be similar to diesel hammers.[12]
Hydraulic press-in equipment installs piles using hydraulic rams to press piles into the ground. This system is preferred where vibration is a concern. There are press attachments that can adapt to conventional pile driving rigs to press 2 pairs of sheet piles simultaneously. Other types of press equipment sit atop existing sheet piles and grip previously driven piles. This system allows for greater press-in and extraction force to be used since more reaction force is developed.[12] The reaction-based machines operate at only 69 dB at 23 ft allowing for installation and extraction of piles in close proximity to sensitive areas where traditional methods may threaten the stability of existing structures.
Such equipment and methods are specified in portions of the internal drainage system in the New Orleans area after Hurricane Katrina, as well as projects where noise, vibration and access are a concern.
Vibratory pile hammers contain a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed so that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. The pile driving machine positioned over the pile with an excavator or crane, and is fastened to the pile by a clamp and/or bolts. Vibratory hammers can drive or extract a pile. Extraction is commonly used to recover steel I-beams used in temporary foundation shoring. Hydraulic fluid is supplied to the driver by a diesel engine-powered pump mounted in a trailer or van, and connected to the driver head via hoses. When the pile driver is connected to a dragline excavator, it is powered by the excavator's diesel engine. Vibratory pile drivers are often chosen to mitigate noise, as when the construction is near residences or office buildings, or when there is insufficient vertical clearance to permit use of a conventional pile hammer (for example when retrofitting additional piles to a bridge column or abutment footing). Hammers are available with several different vibration rates, ranging from 1200 vibrations per minute to 2400 VPM. The vibration rate chosen is influenced by soil conditions and other factors, such as power requirements and equipment cost.
A piling rig is a large track-mounted drill used in foundation projects which require drilling into sandy soil, clay, silty clay, and similar environments. Such rigs are similar in function to oil drilling rigs, and can be equipped with a short screw (for dry soil), rotary bucket (for wet soil) or core drill (for rock), along with other options. Expressways, bridges, industrial and civil buildings, diaphragm walls, water conservancy projects, slope protection, and seismic retrofitting are all projects which may require piling rigs.
The underwater sound pressure caused by pile-driving may be deleterious to nearby fish.[13][14] State and local regulatory agencies manage environment issues associated with pile-driving.[15] Mitigation methods include bubble curtains, balloons, internal combustion water hammers.[16]
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