In engineering, afoundation is the element of astructure which connects it to the ground or more rarely, water (as withfloating structures), transferringloads from the structure to the ground. Foundations are generally considered eithershallow ordeep.[1] Foundation engineering is the application ofsoil mechanics androck mechanics (geotechnical engineering) in the design of foundation elements of structures.
The design and the construction of a well-performing foundation must possess some basic requirements:[2]
The design and the construction of the foundation is done such that it can sustain as well as transmit the dead and the imposed loads to the soil. This transfer has to be carried out without resulting in any form of settlement that can cause stability issues for the structure.
Differential settlements can be avoided by having a rigid base for the foundation. These issues are more pronounced in areas where the superimposed loads are not uniform in nature.
Based on the soil and area it is recommended to have a deeper foundation so that it can guard any form of damage or distress. These are mainly caused due to the problem of shrinkage and swelling because of temperature changes.
The location of the foundation chosen must be an area that is not affected or influenced by future works or factors.
Buildings and structures have a long history of being built with wood in contact with the ground.[3][4]Post in ground construction may technically have no foundation.Timber pilings were used on soft or wet ground even below stone or masonry walls.[5] In marine construction and bridge building a crisscross of timbers or steel beams in concrete is called grillage.[6]
Perhaps the simplest foundation is the padstone, a single stone which both spreads the weight on the ground and raises the timber off the ground.[7]Staddle stones are a specific type of padstone.
Dry stone and stones laid inmortar to build foundations are common in many parts of the world. Dry laid stone foundations may have been painted with mortar after construction. Sometimes the top, visible course of stone is hewn, quarried stones.[8] Besides using mortar, stones can also be put in agabion.[9] One disadvantage is that if using regular steelrebars, the gabion would last much less long than when using mortar (due to rusting). Usingweathering steel rebars could reduce this disadvantage somewhat.
Rubble trench foundations are a shallow trench filled with rubble or stones. These foundations extend below thefrost line and may have a drain pipe which helps groundwater drain away. They are suitable for soils with a capacity of more than 10 tonnes/m2 (2,000 pounds per square foot).
Drawing of Poteaux-en-Terrepost in ground type of wall construction (this example technically calledpallisade construction) in the Beauvais House in Ste Genevieve, Missouri
Black Eagle Dam – cross-section of construction plans for 1892 structure
Davis House dry-laid stone foundation ruin, Gardiner, NY
A basic type of rubble trench foundation
Typical residential poured concrete foundation, except for the lack ofanchor bolts. The concrete walls are supported on continuous footings. There is also aconcrete slab floor. Note the standing water in the perimeterFrench drain trenches.
Often calledfootings, are usually embedded about a meter or so intosoil. One common type is the spread footing which consists of strips or pads of concrete (or other materials) which extend below thefrost line and transfer the weight from walls and columns to the soil orbedrock.
Another common type of shallow foundation is the slab-on-grade foundation where the weight of the structure is transferred to the soil through aconcrete slab placed at the surface. Slab-on-grade foundations can be reinforced mat slabs, which range from 25 cm to several meters thick, depending on the size of the building, or post-tensioned slabs, which are typically at least 20 cm for houses, and thicker for heavier structures.
Another way to install ready-to-build foundations that is more environmentally friendly is to usescrew piles. Screw pile installations have also extended to residential applications, with many homeowners choosing a screw pile foundation over other options. Some common applications for helical pile foundations include wooden decks, fences, garden houses, pergolas, and carports.
Used to transfer the load of a structure down through the upper weak layer oftopsoil to the stronger layer ofsubsoil below. There are different types of deep footings including impact driven piles, drilled shafts,caissons,screw piles, geo-piers[clarification needed] and earth-stabilized columns[clarification needed]. The naming conventions for different types of footings vary between different engineers. Historically, piles werewood, latersteel,reinforced concrete, andpre-tensioned concrete.
A type ofdeep foundation which uses a single, generally large-diameter, structural element embedded into the earth to support all the loads (weight, wind, etc.) of a large above-surface structure.
Many monopile foundations[10] have been used in recent years for economically constructingfixed-bottomoffshore wind farms in shallow-watersubsea locations.[11] For example, a singlewind farmoff the coast of England went online in 2008 with over 100 turbines, each mounted on a 4.74-meter-diameter monopile footing in ocean depths up to 16 meters of water.[12]
A floating foundation is one that sits on a body of water, rather than dry land. This type of foundation is used for somebridges and floating buildings.
Inadequate foundations in muddy soils below sea level caused these houses in the Netherlands tosubside.
Foundations are designed to have an adequate load capacity depending on the type of subsoil/rock supporting the foundation by ageotechnical engineer, and the footing itself may be designed structurally by astructural engineer. The primary design concerns aresettlement andbearing capacity. When considering settlement, total settlement and differential settlement is normally considered. Differential settlement is when one part of a foundation settles more than another part. This can cause problems to the structure which the foundation is supporting.Expansive clay soils can also cause problems.
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