Shallow foundation

A shallow foundation is a type of building foundation that transfers building loads to the earth very near to the surface, rather than to a subsurface layer or a range of depths as does a deep foundation. Shallow foundations include spread footing foundations, mat-slab foundations, slab-on-grade foundations, pad foundations, rubble trench foundations and earthbag foundations.

Shallow foundation construction example

Spread footing foundation

Photography by Victor Albert Grigas (1919-2017) 00140 (37506832366)
a foundation of what would become a one-story house in the United States circa 1955
Wall-foundation
In ground reinforced concrete foundation in cyclonic area, Northern Australia.
In-ground-foundation
In ground reinforced concrete foundation in cyclonic area, Northern Australia.

A spread footing foundation, which is common in residential buildings, has a wider bottom portion than the load-bearing foundation walls it supports. This wider part "spreads" the weight of the structure over more area for greater stability.

The design and layout of spread footings is controlled by several factors, foremost of which is the weight (load) of the structure it must support, penetration of soft near-surface layers, and penetration through near-surface layers likely to change volume due to frost heave or shrink-swell.

These foundations are common in residential construction that includes a basement, and in many commercial structures. But for high rise buildings they are not sufficient. A spread footing that changes elevation in a series of vertical steps so that it follows the contours of a sloping site or accommodates changes in soil strata, is called a stepped footing.

Mat-slab foundations

Mat-slab foundations distribute heavy column and wall loads across the entire building area, to lower the contact pressure compared to conventional spread footings. Mat-slab foundations can be constructed near the ground surface, or at the bottom of basements. In high-rise buildings, mat-slab foundations can be several meters thick, with extensive reinforcing to ensure relatively uniform load transfer.

Slab-on-grade foundation

Slab on grade
Example of slab on grade foundation
Raft-slab
Raft slab house foundation in cyclonic area, Northern Australia.
Raft-slab
Raft slab house foundation in cyclonic area, Northern Australia.

Slab-on-grade or floating slab foundations are a structural engineering practice whereby the concrete slab that is to serve as the foundation for the structure is formed from a mold set into the ground. The concrete is then placed into the mold, 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.

The advantages of the slab technique are that it is cheap and sturdy, and is considered less vulnerable to termite infestation because there are no hollow spaces or wood channels leading from the ground to the structure (assuming wood siding, etc., is not carried all the way to the ground on the outer walls).

The disadvantages are the lack of access from below for utility lines, the potential for large heat losses where ground temperatures fall significantly below the interior temperature, and a very low elevation that exposes the building to flood damage in even moderate rains. Remodeling or extending such a structure may also 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 are commonly 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.[1] 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.

Rubble trench foundation

Rubbletrench
A cross section view of a rubble trench foundation

The rubble trench foundation, a construction approach popularized by architect Frank Lloyd Wright, is a type of foundation that uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more environmentally friendly than other types of foundation because cement manufacturing requires the use of enormous amounts of energy. However, some soil environments (such as particularly expansive or poor load-bearing (< 1 ton/sf) soils) are not suitable for this kind of foundation.

A foundation must bear the structural loads imposed upon it and allow proper drainage of ground water to prevent expansion or weakening of soils and frost heaving. While the far more common concrete foundation requires separate measures to ensure good soil drainage, the rubble trench foundation serves both foundation functions at once.

To construct a rubble trench foundation a narrow trench is dug down below the frost line. The bottom of the trench would ideally be gently sloped to an outlet. Drainage tile, graded 1:8 to daylight, is then placed at the bottom of the trench in a bed of washed stone protected by filter fabric. The trench is then filled with either screened stone (typically 1-1/2") or recycled rubble. A stem wall is then constructed, or a steel-reinforced concrete daro beam is poured at the surface to provide ground clearance for the structure.

The rubble-trench foundation is a relatively simple, low-cost, and environmentally-friendly alternative to a conventional foundation, but may require an engineer's approval if building officials are not familiar with it. Frank Lloyd Wright used them successfully for more than 50 years in the first half of the 20th century, and there is a revival of this style of foundation with the increased interest in green building.

Earthbag foundation

The basic construction method begins by digging a trench down to undisturbed mineral subsoil. Rows of woven bags (or tubes) are filled with available material, placed into this trench, compacted with a pounder to around 1/3 thickness of pre-pounded thickness, and form a foundation. Each successive layer has one or more strands of barbed wire placed on top. This digs into the bag's weave to prevent subsequent layers from slipping, and also resists any tendency for the outward expansion of walls. The next row of bags is offset by half a bag's width to form a staggered pattern. These are either pre-filled with material and delivered, or filled in place (often the case with Superadobe). The weight of this earth-filled bag pushes down on the barbed wire strands, locking the bag in place on the row below. The same process continues layer upon layer, forming walls. A roof can be formed by gradually sloping the walls inward to construct a dome. Traditional types of roof can also be made.

See also

References

  1. ^ "Slab Leak Repair McKinney, Frisco, and Allen Tx - Hackler Plumbing". Hacklerplumbingmckinney.com. 2013-11-08. Retrieved 2018-08-20.

External links

10 Downing Street

10 Downing Street, also known colloquially in the United Kingdom simply as Number 10, is (along with the adjoining Cabinet Office at 70 Whitehall) the headquarters of the Government of the United Kingdom and the official residence and office of the First Lord of the Treasury, a post which, for much of the 18th and 19th centuries and invariably since 1905, has been held by the Prime Minister of the United Kingdom.

Situated in Downing Street in the City of Westminster, London, Number 10 is over 300 years old and contains approximately 100 rooms. A private residence occupies the third floor and there is a kitchen in the basement. The other floors contain offices and conference, reception, sitting and dining rooms where the Prime Minister works, and where government ministers, national leaders and foreign dignitaries are met and entertained. At the rear is an interior courtyard and a terrace overlooking a half-acre (0.2 ha) garden. Adjacent to St James's Park, Number 10 is near Buckingham Palace, the London residence of the British monarch, and the Palace of Westminster, the meeting place of both houses of parliament.

Originally three houses, Number 10 was offered to Sir Robert Walpole by King George II in 1732. Walpole accepted on the condition that the gift was to the office of First Lord of the Treasury rather than to him personally. Walpole commissioned William Kent to join the three houses and it is this larger house that is known as Number 10 Downing Street.

The arrangement was not an immediate success. Despite its size and convenient location near to Parliament, few early Prime Ministers lived there. Costly to maintain, neglected, and run-down, Number 10 was close to being demolished several times but the property survived and became linked with many statesmen and events in British history. In 1985 Margaret Thatcher said Number 10 had become "one of the most precious jewels in the national heritage".

Altendorf (megalithic tomb)

The Altendorf tomb (German: Steinkammergrab von Altendorf) was an important megalithic tomb at Altenburg near Naumburg, northern Hesse, Germany. It was a gallery grave belonging to the Late Neolithic Wartberg culture. The Altenburg tomb is of special significance in Central European prehistory because of the large number of individuals it contained.

Civil engineering

Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, canals, dams, airports, sewerage systems, pipelines, structural components of buildings, and railways. Civil engineering is traditionally broken into a number of sub-disciplines. It is considered the second-oldest engineering discipline after military engineering, and it is defined to distinguish non-military engineering from military engineering. Civil engineering takes place in the public sector from municipal through to national governments, and in the private sector from individual homeowners through to international companies.

Cold Regions Research and Engineering Laboratory

The Cold Regions Research and Engineering Laboratory (CRREL) is a United States Army Corps of Engineers, Engineer Research and Development Center research facility headquartered in Hanover, New Hampshire, that provides scientific and engineering support to the U.S. government and its military with a core emphasis on cold environments. CRREL also provides technical support to non-government customers.

CRREL arose from a consolidation of three antecedent organizations whose purpose was to understand frozen ground, permafrost, snow and ice as factors which were important in strategic northern areas during the Cold War. In its first 25 years CRREL researchers contributed to the understanding of polar ice caps, permafrost, and the engineering technology for developing natural resources in cold climates, such as Alaska. More recently, CRREL researchers have made contributions to science in climate change, the understanding of wave propagation for sensor systems, the control of snow on structures and ice in navigable waterways, and the environmental remediation of military installations.

Concrete

Concrete, usually Portland cement concrete, is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens over time—most frequently a lime-based cement binder, such as Portland cement, but sometimes with other hydraulic cements, such as a calcium aluminate cement. It is distinguished from other, non-cementitious types of concrete all binding some form of aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder.

When aggregate is mixed together with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts chemically with the water and other ingredients to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix or the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.

Famous concrete structures include the Hoover Dam, the Panama Canal and the Roman Pantheon. The earliest large-scale users of concrete technology were the ancient Romans, and concrete was widely used in the Roman Empire. The Colosseum in Rome was built largely of concrete, and the concrete dome of the Pantheon is the world's largest unreinforced concrete dome. Today, large concrete structures (for example, dams and multi-story car parks) are usually made with reinforced concrete.

After the Roman Empire collapsed, use of concrete became rare until the technology was redeveloped in the mid-18th century. Worldwide, concrete has overtaken steel in tonnage of material used.

Deep foundation

A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths.

A pile or piling is a vertical structural element of a deep foundation, driven or drilled deep into the ground at the building site.

There are many reasons that a geotechnical engineer would recommend a deep foundation over a shallow foundation, such as for a skyscraper. Some of the common reasons are very large design loads, a poor soil at shallow depth, or site constraints 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.

Eastern span replacement of the San Francisco–Oakland Bay Bridge

The eastern span replacement of the San Francisco–Oakland Bay Bridge was a construction project to replace a seismically unsound portion of the Bay Bridge with a new self-anchored suspension bridge (SAS) and a pair of viaducts. The bridge is in the U.S. state of California and crosses the San Francisco Bay between Yerba Buena Island and Oakland. It was built between 2002 and 2013 and does not have a name other than the unofficial name of the bridge as a whole ("San Francisco-Oakland Bay Bridge"). The eastern span replacement is the most expensive public works project in California history, with a final price tag of $6.5 billion, a 2,500% cost overrun from the original estimate of $250 million. Originally scheduled to open in 2007, several problems delayed the opening until September 2, 2013. With a width of 258.33 ft (78.74 m), comprising 10 general-purpose lanes, it is currently the world's widest bridge, according to Guinness World Records.The Bay Bridge has two major sections: the western suspension spans and their approach structures between San Francisco and Yerba Buena Island (YBI) and the structures between YBI and the eastern terminus in Oakland. The original eastern section was composed of a double balanced cantilever span, five through-truss spans, and a truss causeway.

The original spans of the bridge east of Yerba Buena Island became the subject of concern after a section collapsed during the Loma Prieta earthquake on October 17, 1989. The replacement span is engineered to withstand the largest earthquake expected over a 1500-year period, and it is expected to last at least 150 years with proper maintenance.

Foundation (engineering)

In engineering, a foundation is the element of a structure which connects it to the ground, and transfers loads from the structure to the ground. Foundations are generally considered either shallow or deep. Foundation engineering is the application of soil mechanics and rock mechanics (Geotechnical engineering) in the design of foundation elements of structures.

Gerald Ratner Athletics Center

The Gerald Ratner Athletics Center is a $51 million athletics facility within the University of Chicago campus in the Hyde Park community area on the South Side of Chicago, Illinois in the United States. The building was named after University of Chicago alumnus, Gerald Ratner. The architect of this suspension structure that is supported by masts, cables and counterweights was César Pelli, who is best known as the architect of the Petronas Towers.

The Ratner Athletics Center was approved for use in September 2003. The facility includes, among other things: a competition gymnasium, a multilevel fitness facility, an Olympic-sized swimming pool, a multipurpose dance studio, meeting room space, and athletic department offices. It serves as home to several of the university's athletic teams and has hosted numerous National Collegiate Athletic Association Division III regional and University Athletic Association conference championship events.

Located at the southwest corner of Ellis Avenue and 55th Street, the Ratner Center has an award-winning design that substitutes a complex external mast and counterweight system for interior support devices to allow for large open-space areas inside the building. Cesar Pelli & Associates Inc. was credited as the design architect and OWP/P was the architect of record.

Glossary of structural engineering

Most of the terms listed in Wikipedia glossaries are already defined and explained within Wikipedia itself. However, glossaries like this one are useful for looking up, comparing and reviewing large numbers of terms together. You can help enhance this page by adding new terms or writing definitions for existing ones.

This glossary of structural engineering terms pertains specifically to structural engineering and its sub-disciplines. Please see glossary of engineering for a broad overview of the major concepts of engineering.

Groundworker

A groundworker is a British term for a subcontractor who is employed to prepare a home construction site for the shallow foundation of a new home.

Typically, the groundworker clears the site, lays a foundation, installs drainage and other pipework, and may build roads if necessary.

The groundworkers are usually the first and last trades performed on site. They will start the job putting in levels, digging the ground, excavating and concreting the foundations, and building the foundations until the floor is on and the work is up to the damp proof course (dpc).

They are also the team responsible for the drainage; connecting to the existing pipes installing in the new pipes.

At the end of a home build, groundworkers return to put in driveways and footpaths.

Groundworkers usually work on a labour, plant and material basis.

House-building

House-building is the construction of houses.

May 1998 Afghanistan earthquake

An earthquake occurred in northern Afghanistan on 30 May 1998, at 06:22 UTC in the Takhar Province with a moment magnitude of 6.5 and a maximum Mercalli intensity of VII (Very strong). At the time, the Afghan Civil War was underway; the affected area was controlled by the United Islamic Front for the Salvation of Afghanistan (the "Northern Alliance").

Olton

Olton is an area/suburban village within the Metropolitan Borough of Solihull in the West Midlands, England. In the 13th century, the Lords of the Manor moved their seat and formed a new settlement, at the junction of two major roads. It was then that Ulverlei was being referred to as ‘Oulton’ (meaning ‘old town’) to distinguish itself from nearby Solihull. Historically within the county of Warwickshire, the village has gradually become contiguous with Solihull to the southeast, though it retains the character of a large independent village.

It is located on the A41 between Solihull town centre 4 miles (6.4 km), Acocks Green, 2 miles (3.2 km) and Birmingham 5.7 miles (9.2 km). Dating back over a 1,000 years, it is a now a residential suburb. Many of the large houses built in St. Bernard's Road, Grange Road and Kineton Green Road during the Victorian and Edwardian period form part of one of Solihull's conservation areas. Olton carries the motto ‘The Town in the Country’.

Princes Risborough

Princes Risborough () is a small town in Buckinghamshire, England, about 9 miles south of Aylesbury and 8 miles north west of High Wycombe. Bledlow lies to the west and Monks Risborough to the east. It lies at the foot of the Chiltern Hills, at the north end of a gap or pass through the Chilterns, the south end of which is at West Wycombe. The A4010 road follows this route from West Wycombe through the town and then on to Aylesbury.

Historically it was both a manor and an ecclesiastical parish, of the same extent as the manor, which comprised the present ecclesiastical parish of Princes Risborough (excluding Ilmer) and also the present ecclesiastical parish of Lacey Green, which became a separate parish in the 19th century. It was long and narrow (a "strip parish"), taking in land below the Chiltern scarp, the slope of the scarp itself and also land above the scarp extending into the Chiltern hills. The manor and the parish extended from Longwick in the north through Alscot, the town of Princes Risborough, Loosley Row and Lacey Green to Speen and Walters Ash in the south.

Since 1934 the civil parish of Princes Risborough (formerly the same as the ecclesiastical parish) has included the town of Princes Risborough, the village of Monks Risborough (but not the outlying parts) and part of Horsenden but has excluded Longwick. It is within the Wycombe district of Buckinghamshire and operates as a town council within Wycombe district.

The town is overlooked by the Whiteleaf Cross, carved in the chalk of the hillside, though the cross itself is in Monks Risborough.

Rock of Cashel

The Rock of Cashel (Irish: Carraig Phádraig [ˈcaɾˠəɟ ˈfˠaːd̪ˠɾˠəɟ]), also known as Cashel of the Kings and St. Patrick's Rock, is a historic site located at Cashel, County Tipperary, Ireland.

Strap footing

A strap footing is a component of a building’s foundation. It is a type of combined footing, consisting of two or more column footings connected by a concrete beam. This type of beam is called a strap beam. It is used to help distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings.A strap footing is often used in conjunction with columns that are located along a building’s property or lot line. Typically, columns are centered on column footings, but in conditions where columns are located directly adjacent to the property line, the column footings may be offset so that they do not encroach onto the adjacent property. This results in an eccentric load on a portion of the footing, causing it to tilt to one side. The strap beam restrains the tendency of the footing to overturn by connecting it to nearby footings.

Upper Zohar

Upper Zohar (Hebrew: זהר עילית‎), also Rogem Zohar, is an archaeological site on the outskirts of the Israeli town of Arad. It is believed to be the site of a Byzantine-era fort and part of a Roman line of defense against desert raiders. More recent research has suggested it was constructed for economic rather than military reasons.

Wall footing

A wall footing or strip footing is a continuous strip of concrete that serves to spread the weight of a load-bearing wall across an area of soil. It is the component of a shallow foundation.

Soil
Foundations
Retaining walls
Stability
Earthquakes
Geosynthetics
Numerical analysis

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