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A gravity-type stone retaining wall

A retaining wall is a structure that holds back soil or rock from a building, structure or area. Retaining walls prevent downslope movement or erosion and provide support for vertical or near-vertical grade changes. Cofferdams and bulkheads, structures that hold back water, are sometimes also considered retaining walls. Retaining walls are generally made of masonry, stone, brick, concrete, vinyl, steel or timber. Once popular as an inexpensive retaining material, railroad ties have fallen out of favor due to environmental concerns. They also decompose over time. Image File history File links Broom_icon. ... Image File history File linksMetadata Size of this preview: 450 × 600 pixels Full resolution (1536 × 2048 pixel, file size: 786 KB, MIME type: image/jpeg) Stone retaining wall. ... Image File history File linksMetadata Size of this preview: 450 × 600 pixels Full resolution (1536 × 2048 pixel, file size: 786 KB, MIME type: image/jpeg) Stone retaining wall. ... Loess field in Germany Surface-water-gley developed in glacial till, Northern Ireland For the American hard rock band, see SOiL. For the System of a Down song, see Soil (song). ... This article is about the geological substance. ... For morphological image processing operations, see Erosion (morphology). ... dam stands for dekametre. ... This article refers to the building structure component; for the fraternal organization, see Freemasonry. ... This article is about the geological substance. ... For other uses, see Brick (disambiguation). ... This article is about the construction material. ... Chemical structure of the vinyl functional group. ... For other uses, see Steel (disambiguation). ... Ferroconcrete sleepers A variant fastening of rails to wooden sleepers A railroad tie, cross tie, or sleeper is a rectangular object used as a base for railroad tracks. ...

Segmental retaining walls have gained favor over poured-in-place concrete walls or treated-timber walls. They are more economical, easier to install and more environmentally sound.

The most important consideration in proper design and installation of retaining walls is that the retained material is attempting to move forward and downslope due to gravity. This creates a lateral earth pressure behind the wall which depends on the angle of internal friction (phi) and the cohesive strength (c) of the retained material, as well as the direction and magnitude of movement the retaining structure undergoes. Lateral earth pressures are typically smallest at the top of the wall and increase toward the bottom. Earth pressures will push the wall forward or overturn it if not properly addressed. Also, any groundwater behind the wall that is not dissipated by a drainage system causes an additional horizontal hydraulic pressure on the wall.^[1] An example of lateral earth pressure overturning a retaining wall. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of lithologic formations. ... Hydrostatic pressure is the pressure exerted by a fluid due to its weight. ...

Types of retaining walls

Various types of retaining walls

Gravity

Gravity walls depend on the weight of their mass (stone, concrete or other heavy material) to resist pressures from behind and will often have a slight 'batter' setback, to improve stability by leaning back into the retained soil. For short landscaping walls, they are often made from mortarless stone or segmental concrete units (masonry units)^[2]. Dry-stacked gravity walls are somewhat flexible and do not require a rigid footing in frost areas. Setbacks on the Pyramid of Djoser. ... Mortar holding weathered bricks. ... Frost on black pipes Frost is a solid deposition of water vapor from saturated air. ...

Earlier in the 20th century, taller retaining walls were often gravity walls made from large masses of concrete or stone. Today, taller retaining walls are increasingly built as composite gravity walls such as: geosynthetic or with precast facing; gabions (stacked steel wire baskets filled with rocks), crib walls (cells built up log cabin style from precast concrete or timber and filled with soil) or soil-nailed walls (soil reinforced in place with steel and concrete rods).^[3] Historically, Gabions were round cages with open tops and bottoms, made from wicker and filled with earth for use as fortifications. ...

Sheet piling

Sheet pile walls are often used in soft soils and tight spaces. Sheet pile walls are made out of steel, vinyl, fiberglass or plastic sheet piles or wood planks driven into the ground. Structural design methods for this type of wall exist but these methods are more complex than for a gravity wall. As a rule of thumb; 1/3 third above ground, 2/3 below ground. Taller sheet pile walls usually require a tie-back anchor "dead-man" placed in the soil some distance behind the wall face, that is tied to the wall face, usually by a cable or a rod. Anchors must be placed behind the potential failure plane in the soil. Bundle of fiberglass Fiberglass (also called fibreglass and glass fibre) is material made from extremely fine fibers of glass. ... A deep foundation installation for a bridge in Napa, California. ... I NEED TO FUCK SOMEONE! I AM TIRED OF PORN! SOMEONE HELP ME! ...

Proper drainage behind the wall is critical to the performance of retaining walls. Drainage materials will reduce or eliminate the hydrostatic pressure and increase the stability of the fill material behind the wall, assuming that this is not a retaining wall for water. Drainage is the natural or artificial removal of surface and sub-surface water from a given area. ... Hydrostatic pressure is the pressure exerted by a fluid due to its weight. ...

Cantilevered

Prior to the introduction of modern reinforced-soil gravity walls, cantilevered walls were the most common type of taller retaining wall. Cantilevered walls are made from a relatively thin stem of steel-reinforced, cast-in-place concrete or mortared masonry (often in the shape of an inverted T). These walls cantilever loads (like a beam) to a large, structural footing; converting horizontal pressures from behind the wall to vertical pressures on the ground below. Sometimes cantilevered walls are butressed on the front, or include a counterfort on the back, to improve their stability against high loads. Buttresses are short wing walls at right angles to the main trend of the wall. These walls require rigid concrete footings below seasonal frost depth. This type of wall uses much less material than a traditional gravity wall. A schematic image of two cantilevers. ... A statically determinate beam, bending under an evenly distributed load. ...

Anchored

See also: Tieback (geotechnical)

This version of wall uses cables or other stays anchored in the rock or soil behind it. Usually driven into the material with boring, anchors are then expanded at the end of the cable, either by mechanical means or often by injecting pressurized concrete, which expands to form a bulb in the soil. Technically complex, this method is very useful where high loads are expected, or where the wall itself has to be slender and would otherwise be too weak. A tieback is a horizontal wire used to reinforce retaining walls for stability. ...

Soil nailing

Main article: Soil nailing

Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements - normally steel reinforcing bars. The bars are usually installed into a pre-drilled hole and then grouted into place or drilled and grouted simultaneously. They are usually installed untensioned at a slight downward inclination. A rigid or flexible facing (often sprayed concrete) or isolated soil nail heads may be used at the surface. Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements - normally steel reinforcing bars. ... In civil engineering, earthworks are engineering works created through the moving of massive quantities of soil or unformed stone. ... Grout is a construction material used to embed rebars in masonry walls, connect sections of pre-cast concrete, fill voids, and seal joints (like those between tiles). ...

Soil-strengthened

A number of systems exist that do not simply consist of the wall itself, but reduce the earth pressure acting on the wall itself. These are usually used in combination with one of the other wall types, though some may only use it as facing (i.e. for visual purposes).

Gabion meshes

Main article: Gabion

This type of soil strengthening, often also used without an outside wall, consists of wire mesh 'boxes' into which roughly cut stone or other material is filled. The mesh cages reduce some internal movement/forces, and also reduce erosive forces. Historically, Gabions were round cages with open tops and bottoms, made from wicker and filled with earth for use as fortifications. ... A wire is a single, usually cylindrical, elongated strand of drawn metal. ... For other uses, see Mesh (disambiguation). ...

Mechanical stabilization

Main article: Mechanically stabilized earth

Mechanically stabilized earth, also called MSE, is soil constructed with artificial reinforcing via layered horizontal mats (geosynthetics) fixed at their ends. These mats provide added internal shear resistance beyond that of simple gravity wall structures. Other options include steel straps, also layered. This type of soil strengthening usually needs outer facing walls to affix the layers to and vice versa. A diagram of a mechanically stabilized earth wall as it would be modeled in a finite element analysis. ... Geosynthetics in use Geosynthetics is the catch all term used to describe a range of generally synthetic products used to solve geotechnical problems. ...

The wall face is often of precast concrete units^[2] that can tolerate some differential movement. The reinforced soil's mass, along with the facing, then acts as an improved gravity wall. The reinforced mass must be built large enough to retain the pressures from the soil behind it. Gravity walls usually must be a minimum of 50 to 60 percent as deep or thick as the height of the wall, and may have to be larger if there is a slope or surcharge on the wall.

See also

A mud box retaining wall built to keep out flood waters. Note the buildings on the right-hand side are half-submerged in this May 1973 Mississippi River, USA photo.

• Civil engineering
• Foundation
• Trench shoring
• Trench shield
• Geotechnical engineering
• Structural engineering

ARC Identifier: 552831 IN THE SPRING OF 1973 THE MISSISSIPPI RIVER REACHED ITS HIGHEST LEVEL IN MORE THAN 150 YEARS. UNPRECEDENTED FLOODING OCCURRED THROUGHOUT THE RIVER BASIN. PARTICULARLY AFFECTED WERE THE MARSH AREA BELOW NEW ORLEANS AND THE ENTIRE ATCHAFALAYA RIVER BASIN MORGAN CITY WATERFRONT ON THE ATCHAFALAYA. STRUCTURE IN... ARC Identifier: 552831 IN THE SPRING OF 1973 THE MISSISSIPPI RIVER REACHED ITS HIGHEST LEVEL IN MORE THAN 150 YEARS. UNPRECEDENTED FLOODING OCCURRED THROUGHOUT THE RIVER BASIN. PARTICULARLY AFFECTED WERE THE MARSH AREA BELOW NEW ORLEANS AND THE ENTIRE ATCHAFALAYA RIVER BASIN MORGAN CITY WATERFRONT ON THE ATCHAFALAYA. STRUCTURE IN... For the river in Canada, see Mississippi River (Ontario). ... Motto: (traditional) In God We Trust (official, 1956–present) Anthem: The Star-Spangled Banner Capital Washington, D.C. Largest city New York City Official language(s) None at the federal level; English de facto Government Federal Republic  - President George W. Bush (R)  - Vice President Dick Cheney (R) Independence - Declared - Recognized... The Falkirk Wheel in Scotland. ... A foundation is a structure that transmits loads from a building or road to the underlying ground. ... Bostons Big Dig presented geotechnical challenges in an urban environment. ... Structural engineering is a field of engineering that deals with the design of structural systems with the purpose of supporting and resisting various loads. ...

References

1. ^ Terzaghi, K. (1934), Large Retaining Wall Tests, Engineering News Record Feb. 1, March 8, April 19
2. ^ ^{a b} Segmental Retaining Walls. National Concrete Masonry Association. Retrieved on 2008-03-24.
3. ^ Terzaghi, K. (1943), Theoretical Soil Mechanics, New York: John Wiley and Sons

• 2002, Design Manual for Segmental Retaining Walls, National Concrete Masonry Association, Herndon, VA
• Joseph E. Bowles, 1968, Foundation Analysis and Design, McGraw-Hill Book Company, New York

Karl von Terzaghi (Prague, October 2, 1883 – Winchester, Massachusetts, October 25, 1963) was an Austrian civil engineer and geologist, called the father of soil mechanics. ... 2008 (MMVIII) is the current year, a leap year that started on Tuesday of the Anno Domini (or common era), in accordance to the Gregorian calendar. ... is the 83rd day of the year (84th in leap years) in the Gregorian calendar. ... Karl von Terzaghi (Prague, October 2, 1883 – Winchester, Massachusetts, October 25, 1963) was an Austrian civil engineer and geologist, called the father of soil mechanics. ...

External links

• Pictures of Gravity Walls
• Information on the design of retaining walls