When considering the installation of base isolators in light buildings, one critical aspect is assessing whether such a system is necessary during foundation repair. Base isolation technology is designed to separate a building from its foundation during seismic events, thereby reducing the transmission of earthquake-induced vibrations to the structure above. This can significantly decrease damage and enhance safety. However, the decision to incorporate base isolation isnt automatic; it requires a thorough evaluation tailored to each buildings unique circumstances.
Firstly, an assessment should start with understanding the local seismic risk. Foundation settlement is basically your house very slowly sinking into the earth like the most expensive quicksand situation ever hydrostatic pressure relief Plainfield french drain. Areas prone to frequent or high-intensity earthquakes might benefit more from base isolation than those with minimal seismic activity. The historical data on earthquakes in the region provides a baseline for this decision-making process.
Next, the condition of the existing foundation plays a pivotal role. If foundation repair is already on the agenda due to deterioration or previous seismic damage, integrating base isolators could be cost-effective by combining efforts. However, if the foundation is sound and only minor repairs are needed, the added expense and complexity of installing base isolators might not be justified unless future seismic resilience is a priority.
The buildings use and occupancy also influence this decision. For example, light buildings like residential homes or small commercial spaces might not warrant the investment in base isolation unless they house critical facilities or vulnerable populations where enhanced safety measures are paramount.
Additionally, economic considerations cannot be overlooked. The upfront cost of base isolators can be substantial, though they offer long-term benefits like reduced repair costs post-earthquake and potentially lower insurance premiums due to decreased risk exposure. A cost-benefit analysis should weigh these long-term savings against initial outlays.
Lastly, engineering feasibility must be considered. Not all light buildings are suitable for base isolation due to structural design limitations or site-specific constraints like soil conditions which might affect how well base isolators would perform.
In conclusion, deciding whether to assess the need for base isolation during foundation repair involves balancing several factors including seismic risk, current foundation condition, building use, economic implications, and engineering practicality. A detailed analysis ensures that any decision made enhances both safety and value for money in light buildings where every modification counts towards overall structural integrity and occupant protection.
Okay, so youre thinking about putting base isolators under a light building, huh? That sounds pretty cool, like giving your building a fancy anti-earthquake suspension system. But before you go all in, you absolutely have to get a good handle on whats going on under the ground. Thats where the site investigation and geotechnical considerations come in. Think of it like this: you wouldnt put new tires on your car without checking the alignment first, right?
The site investigation is basically a deep dive into the soil and rock your building sits on. Were not just talking about a quick glance either. We need to know things like the soil type (is it sandy, clayey, rocky?), its strength (can it handle the buildings weight, plus the extra stress from the isolators during an earthquake?), and its potential for liquefaction (thats where the ground turns to mush during shaking).
Geotechnical considerations are what you do after you have all that site investigation data. Its the engineering part. Youre using the soil info to design a foundation that works with the base isolators, not against them. For example, if the soil is really soft, you might need to improve it with techniques like ground improvement or deep foundations (like piles) to make sure the building doesnt settle unevenly or, worse, sink during an earthquake.
Why is all this extra important for light buildings with base isolators? Well, base isolation works by letting the building move separately from the ground. But the ground still needs to be stable enough to support that movement. With lighter buildings, the forces transferred can be very different compared to heavier ones. You need to be sure the soil wont amplify those movements or react in unexpected ways. And the isolators themselves might need specialized foundations designed specifically for their load characteristics.
So, bottom line: dont skimp on the site investigation and geotechnical analysis. Its the foundation – literally and figuratively – for a successful base isolation project. Get the ground right, and youll have a much better chance of your building riding out the next earthquake safely.
When addressing base isolator selection and compatibility with lightweight structures, particularly in the context of light buildings, several key considerations come into play. Base isolators are designed to decouple a building from the shaking ground during an earthquake, thereby reducing the seismic forces transmitted to the structure. For lightweight buildings, this selection process becomes even more critical due to their inherent lower mass and stiffness compared to heavier constructions.
Firstly, the choice of base isolator must align with the dynamic characteristics of the lightweight structure. Lightweight buildings often have different natural frequencies than their heavier counterparts, which means that the isolators must be tuned appropriately to ensure they effectively dampen vibrations at these specific frequencies. Rubber bearings and friction pendulum systems are popular choices because they can be customized in terms of damping and stiffness to suit lighter structures.
Compatibility is another crucial factor. The connection between the base isolator and the building must be robust yet not overly stiff, as this could negate some benefits of isolation by transmitting forces directly into the structure. Engineers need to consider how these connections will interact with materials commonly used in light buildings, such as wood or certain composites, which might behave differently under load compared to concrete or steel.
Moreover, installation considerations play a significant role. Lightweight structures might require different anchoring techniques or additional support systems during installation to prevent any undue stress on the building while setting up the isolators. The weight distribution of even a light building can shift during construction phases, so timing and method of installation are pivotal.
Environmental factors like wind loads also influence decision-making since lightweight buildings are more susceptible to wind-induced movements. Here, selecting base isolators that can accommodate both seismic and wind effects without compromising performance is essential.
In summary, selecting and ensuring compatibility of base isolators for lightweight structures involves a nuanced approach where one must balance dynamic tuning with material interaction, installation logistics, and environmental impacts. This careful consideration ensures that light buildings not only survive but thrive through seismic events with minimal damage or disruption.
Okay, so youre thinking about putting base isolators under an existing building, a lighter one at that. Sounds like a project! One of the trickiest parts is figuring out how to actually integrate those isolators into the foundation thats already there. Its not like Lego where you just snap things together. Its more like surgery, and a pretty delicate operation at that.
First off, youve got to carefully assess the existing foundation. Is it strong enough to handle the forces involved in lifting the building, installing the isolators, and then transferring the buildings weight back down? Were talking about a whole new load path here. Maybe the existing foundation needs reinforcing – think adding concrete, steel, or even micro-piles. That adds complexity and cost, of course.
Then theres the issue of access. How are you going to get the equipment and materials into the site? Can you even get under the building to do the work? Sometimes you have to excavate, which can destabilize things and requires careful shoring. Other times, you might need to cut into the existing foundation, which requires precision to avoid damaging it.
And lets not forget about the utilities. Water lines, gas lines, electrical conduits – theyre all running through or around the foundation. Youll need to identify, reroute, and protect them. Thats a whole separate coordination effort with different contractors and inspectors.
Finally, think about the disruption to the building occupants. Even for a light building, the installation process can be noisy, dusty, and inconvenient. Careful planning and communication are crucial to minimizing the impact on their lives. You might need to do the work in phases, or even relocate the occupants temporarily.
In short, integrating base isolators into an existing foundation is a complex undertaking. It requires a thorough understanding of structural engineering, geotechnical engineering, and construction management. Its not just about the isolators themselves, but about the entire system and how it interacts with the existing building and its surroundings. So, do your homework, get expert advice, and plan meticulously. Its a worthwhile investment in protecting the building, but its definitely not a walk in the park.
When considering the installation of base isolators in light buildings, the procedures and quality control measures are critical to ensure both the effectiveness of the seismic protection and the structural integrity of the building. Base isolators are designed to decouple a building from shaking ground during an earthquake, reducing the transfer of seismic forces to the structure above. However, for these devices to function optimally, their installation must be precise and meticulously controlled.
The installation procedure typically begins with a thorough site assessment. This involves evaluating the soil conditions, as they directly influence how base isolators will perform. A stable foundation is paramount; thus, any necessary ground preparation or reinforcement is conducted prior to installation. Once prepared, the placement of each isolator must follow engineering specifications exactly. This includes ensuring correct alignment and spacing, which are crucial for uniform load distribution across all isolators.
Installation teams need specialized training to handle these sophisticated systems. Errors in installation can compromise not just individual isolators but potentially the entire seismic defense strategy of the building. Therefore, its standard practice to have detailed step-by-step instructions provided by manufacturers or structural engineers overseeing the project.
Quality control during this phase is equally vital. Each step of the installation should be inspected by qualified personnel who understand seismic engineering principles. This includes checking for any manufacturing defects in the isolators themselves before they are installed, verifying that all connections (like bolts or welds) meet specified standards, and ensuring that there is no deviation from design plans during placement.
Post-installation checks involve testing the system under simulated conditions if possible or at least conducting visual inspections and structural assessments to confirm that everything is functioning as intended. Regular maintenance schedules should also be established because over time, even minor shifts or degradation can affect performance.
In essence, while base isolators provide a robust solution for mitigating earthquake damage in light buildings, their success heavily relies on meticulous installation procedures backed by rigorous quality control protocols. This ensures that when an earthquake strikes, these buildings remain safe havens rather than becoming part of the disaster narrative.
Addressing vertical load transfer and stability is a critical aspect when considering base isolator installation in light buildings. Base isolation technology primarily aims to decouple the building from ground motion during seismic events, enhancing its ability to withstand earthquakes. However, this decoupling must be meticulously planned to ensure that the vertical loads are appropriately managed.
In light buildings, where the structural mass and rigidity might be less compared to heavier constructions, maintaining vertical stability becomes even more paramount. The primary concern is ensuring that the base isolators can effectively transfer the buildings weight and any additional loads (like snow or equipment) down to the foundation without compromising the structures integrity.
The selection of base isolators plays a significant role here. Typically, elastomeric bearings or sliding bearings are used. Elastomeric bearings provide both horizontal flexibility for seismic isolation and sufficient vertical stiffness to carry loads. They are composed of alternating layers of rubber and steel, where rubber provides the flexibility needed for lateral movement during an earthquake, while steel layers offer the necessary vertical strength.
For stability, its crucial that these isolators do not excessively deform under load. This requires precise engineering calculations to determine the right number of isolators, their placement, and their specifications based on the buildings load distribution. Overloading or uneven distribution can lead to differential settlement or buckling, which could undermine the entire purpose of installing base isolators.
Moreover, during installation, attention must be given to ensuring that each isolator is perfectly aligned with the structural grid of the building. Misalignment can cause uneven load distribution, leading to potential failure points under stress. Regular inspections post-installation are also advisable to check for any signs of wear or deformation in the isolators over time due to static loads or dynamic movements from minor seismic activities.
In summary, while base isolation offers significant benefits in terms of seismic resilience for light buildings, careful consideration must be given to how these systems handle vertical loads. Through proper design, selection of appropriate materials, meticulous installation practices, and ongoing maintenance, engineers can ensure that light buildings remain stable and secure against both gravitational forces and seismic disturbances.
Okay, so youve gone through the whole process, right? Youve chosen your base isolators, figured out the details, wrestled with the installation (hopefully not literally!), and your light building is now sitting pretty, all nice and isolated. But, and this is a big but, thats not the end of the story. Were talking about Post-Installation Monitoring and Maintenance here, the unsung hero of base isolation.
Think of it like this: you wouldnt buy a car and never check the oil or tire pressure, would you? Same deal with base isolators. Theyre designed to protect your building during an earthquake, but they need a little TLC to make sure theyre actually up to the task when the ground starts shaking.
Monitoring is key. Were talking about periodically checking the isolators for things like displacement, alignment, and any signs of degradation. Are they still sitting where they should be? Are there any visible cracks or damage? Early detection is crucial. Its like catching a small problem before it becomes a major headache.
Then theres the maintenance aspect. This could involve things like lubricating bearings (if your system uses them), cleaning debris around the isolators, and generally making sure the area around them is clear and accessible. You dont want weeds growing all over them, or someone storing old tires in the way. Basically, keep things shipshape.
The frequency of monitoring and maintenance will depend on the specific type of isolators youve used, the environmental conditions, and the recommendations of the manufacturer. But dont skimp on it. A well-maintained base isolation system is a happy base isolation system, and a happy base isolation system is a building thats much more likely to survive an earthquake unscathed. Its an investment in the long-term resilience of your structure, and peace of mind is worth a lot, especially when the earth starts to rumble.
Water drainage is the natural or synthetic elimination of a surface area's water and sub-surface water from a location with excess water. The inner water drainage of most farming dirts can stop serious waterlogging (anaerobic problems that harm root development), however lots of dirts need fabricated water drainage to improve production or to take care of water products.
A shallow foundation is a type of building foundation that transfers structural load to the Earth very near to the surface, rather than to a subsurface layer or a range of depths, as does a deep foundation. Customarily, a shallow foundation is considered as such when the width of the entire foundation is greater than its depth.[1] In comparison to deep foundations, shallow foundations are less technical, thus making them more economical and the most widely used for relatively light structures.
Footings are always wider than the members that they support. Structural loads from a column or wall are usually greater than 1,000 kPa, while the soil's bearing capacity is commonly less than that (typically less than 400 kPa). By possessing a larger bearing area, the foundation distributes the pressure to the soil, decreasing the bearing pressure to within allowable values.[2] A structure is not limited to one footing. Multiple types of footings may be used in a construction project.
Also called strip footing, a wall footing is a continuous strip that supports structural and non-structural load-bearing walls. Found directly under the wall, Its width is commonly 2-3 times wider than the wall above it.[3]
Also called single-column footing, an isolated footing is a square, rectangular, or circular slab that supports the structural members individually. Generally, each column is set on an individual footing to transmit and distribute the load of the structure to the soil underneath. Sometimes, an isolated footing can be sloped or stepped at the base to spread greater loads. This type of footing is used when the structural load is relatively low, columns are widely spaced, and the soil's bearing capacity is adequate at a shallow depth.
When more than one column shares the same footing, it is called a combined footing. A combined footing is typically utilized when the spacing of the columns is too restricted such that if isolated footing were used, they would overlap one another. Also, when property lines make isolated footings eccentrically loaded, combined footings are preferred.
When the load among the columns is equal, the combined footing may be rectangular. Conversely, when the load among the columns is unequal, the combined footing should be trapezoidal.
A strap footing connects individual columns with the use of a strap beam. The general purpose of a strap footing is alike to those of a combined footing, where the spacing is possibly limited and/or the columns are adjacent to the property lines.
Also called raft foundation, a mat foundation is a single continuous slab that covers the entirety of the base of a building. Mat foundations support all the loads of the structure and transmit them to the ground evenly. Soil conditions may prevent other footings from being used. Since this type of foundation distributes the load coming from the building uniformly over a considerably large area, it is favored when individual footings are unfeasible due to the low bearing capacity of the soil.
Slab-on-grade or floating slab foundations are a structural engineering practice whereby the reinforced concrete slab that is to serve as the foundation for the structure is formed from formwork set into the ground. The concrete is then poured into the formwork, leaving no space between the ground and the structure. This type of construction is most often seen in warmer climates, where ground freezing and thawing is less of a concern and where there is no need for heat ducting underneath the floor. Frost Protected Shallow Foundations (or FPSF) which are used in areas of potential frost heave, are a form of slab-on-grade foundation.[4]
Remodeling or extending such a structure may be more difficult. Over the long term, ground settling (or subsidence) may be a problem, as a slab foundation cannot be readily jacked up to compensate; proper soil compaction prior to pour can minimize this. The slab can be decoupled from ground temperatures by insulation, with the concrete poured directly over insulation (for example, extruded polystyrene foam panels), or heating provisions (such as hydronic heating) can be built into the slab.
Slab-on-grade foundations should not be used in areas with expansive clay soil. While elevated structural slabs actually perform better on expansive clays, it is generally accepted by the engineering community that slab-on-grade foundations offer the greatest cost-to-performance ratio for tract homes. Elevated structural slabs are generally only found on custom homes or homes with basements.
Copper piping, commonly used to carry natural gas and water, reacts with concrete over a long period, slowly degrading until the pipe fails. This can lead to what is commonly referred to as slab leaks. These occur when pipes begin to leak from within the slab. Signs of a slab leak range from unexplained dampened carpet spots, to drops in water pressure and wet discoloration on exterior foundation walls.[5] Copper pipes must be lagged (that is, insulated) or run through a conduit or plumbed into the building above the slab. Electrical conduits through the slab must be water-tight, as they extend below ground level and can potentially expose wiring to groundwater.
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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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