FACTOID # 7: The top five best educated states are all in the Northeast.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Geotechnical engineering
Boston's Big Dig presented geotechnical challenges in an urban environment.
Boston's Big Dig presented geotechnical challenges in an urban environment.

Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. Geotechnical engineering includes investigating existing subsurface conditions and materials; assessing risks posed by site conditions; designing earthworks and structure foundations; and monitoring site conditions, earthwork and foundation construction. View of Bostons Big Dig from the air. ... View of Bostons Big Dig from the air. ... Nickname: City on the Hill, Beantown, The Hub (of the Universe)1, Athens of America, The Cradle of Revolution, Puritan City, Americas Walking City Location in Massachusetts, USA Counties Suffolk County Mayor Thomas M. Menino(D) Area    - City 232. ... Metropolitan Highway System Big Dig is the unofficial name of the Central Artery/Tunnel Project (CA/T), a megaproject to reroute the Central Artery (Interstate 93), the chief controlled-access highway through the heart of Boston, Massachusetts, into a 3. ... The Falkirk Wheel in Scotland. ...


A typical geotechnical engineering project begins with a site investigation of soil and bedrock on and below an area of interest to determine their engineering properties including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include the assessment of the risk to humans, property and the environment from natural hazards such as earthquakes, landslides, sinkholes, soil liquefaction, debris flows and rock falls. SOiL is a five-piece hard rock music group from Chicago, Illinois. ... Bedrock is the native consolidated rock underlying the Earths surface. ... In large construction projects, such as skyscrapers, cranes are essential. ... Global earthquake epicenters, 1963–1998. ... This entry refers to the geological term landslide. ... Sinkholes are formed by the collapse of cave roofs and are a feature of landscapes that are based on limestone bedrock. ... Soil Liquefaction is the process by which saturated, unconsolidated soil or sand is converted into a suspension. ...


A geotechnical engineer then determines and designs the type of foundations, earthworks, and/or pavement subgrades required for the intended man-made structures to be built. Foundations are designed and constructed for structures of various sizes such as high-rise buildings, bridges, medium to large commercial buildings, and smaller structures where the soil conditions do not allow code-based design. A log bridge in the French Alps near Vallorcine. ...


Foundations built for above-ground structures include shallow and deep foundations. Retaining structures include earth-filled dams and retaining walls. Earthworks include embankments, tunnels, levees, channels, reservoirs, deposition of hazardous waste and sanitary landfills. DAMS is a racing team from France, involved in many areas of motorsports. ... Embankment can be: An artificial slope which can be made out of earth, stones or bricks, or a combination of these. ... An underground pedestrian tunnel between buildings at MIT. Note the utility pipes running along the ceiling. ... This article is about the type of dam. ... For the geographical meanings of this word, see channel (geography). ... A reservoir (French: réservoir) is an artificial lake created by flooding land behind a dam. ... Hazardous waste is waste that poses substantial or potential threats to public health or the environment and generally exhibits one or more of these characteristics: ignitability corrosivity reactivity toxicity Generally, toxicity is quantified through the use of the Toxicity Characteristic Leaching Procedure or TCLP test, as required by EPA. Hazardous... Landfill can also refer to Land reclamation. ...


Geotechnical engineering is also related to coastal and ocean engineering. Coastal engineering can involve the design and construction of wharves, marinas, and jetties. Ocean engineering can involve foundation and anchor systems for offshore structures such as oil platforms. Ocean engineering is the branch of engineering concerned with the design, analysis and operation of systems that operate in an oceanic environment. ... A wharf (plural wharfs, or (especially in American English) wharves, collectively wharfing or wharfage) is a fixed platform, commonly on pilings, roughly parallel to and alongside navigable water, where ships are loaded and unloaded. ... For other uses of this word, see Marina (disambiguation). ... Coastal lagoons fronted by barrier spits typically have entrances that migrate through time. ... Offshore structure has two principal meanings: Financial, with reference to offshore vehicles formed in Offshore Financial Centres. ... An oil platform is a large structure used to house workers and machinery needed to drill and then produce oil and natural gas in the ocean. ...


The fields of geotechnical engineering and engineering geology are closely related, and intersect in some areas. However, the field of geotechnical engineering is a specialty of engineering, where the field of engineering geology is a specialty of geology. Engineering Geology is the application of the science of geology to the understanding of geologic phenomena and the engineering solution of geologic hazards and other geologic problems for society. ... Engineering is the design, analysis, and/or construction of works for practical purposes. ... Engineering Geology is the application of the science of geology to the understanding of geologic phenomena and the engineering solution of geologic hazards and other geologic problems for society. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ...

Contents

History

Karl Terzaghi (1883 - 1963) is generally recognized as the father of modern soil mechanics and geotechnical engineering. [1] Karl von Terzaghi (Prague, October 2, 1883 – Winchester, Massachusetts, October 25, 1963) was an Austrian civil engineer, called the father of soil mechanics. ...


Practicing engineers

Geotechnical engineers are typically graduates of a four-year civil engineering program and often hold a masters degree. Governments usually license and regulate practicing geotechnical engineers. In the United States, state governments will typically license engineers who have graduated from an ABET accredited school, completed several years of work experience, and passed the professional engineering examination.[2] California has an additional licensing program for geotechnical engineers who have already obtained licensure as civil engineers. A masters degree is an academic degree usually awarded for completion of a postgraduate course of one or two years in duration. ... The Accredition Board for Engineering and Technology (ABET) is a non-profit organization that serves the public by making accreditations of the universities and scientific institutions which live up to certain qualities defined by the organization. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Official language(s) English Capital Sacramento Largest city Los Angeles Area  Ranked 3rd  - Total 158,302 sq mi (410,000 km²)  - Width 250 miles (400 km)  - Length 770 miles (1,240 km)  - % water 4. ... This is a list of civil engineers, people who were trained in or practiced civil engineering. ...


Soil mechanics

Main articles: Soil mechanics and Rock mechanics

In geotechnical engineering, soils are considered a three-phase material composed of: rock or mineral particles, water and air. The voids of a soil, the spaces in between mineral particles, contain the water and air. Soil mechanics is a discipline that applies the principles of engineering mechanics to soil to predict the mechanical behavior of soil. ... Rock mechanics is the theoretical and applied science of the mechanical behaviour of rock and rock masses; it is that branch of mechanics concerned with the response of rock and rock masses to the force fields of their physical environment. ... Minerals are natural compounds formed through geological processes. ...


The engineering properties of soils are affected by four main factors: the predominant size of the mineral particles, the type of mineral particles, the grain size distribution, and the relative quantities of mineral, water and air present in the soil matrix. Fine particles (fines) are defined as particles less than 0.075 mm in diameter.


Basic soil properties

Bulk density 
Total unit weight: Cumulative weight of the solid particles, water and air in the material per unit volume. Note that the air phase is often assumed to be weightless.
Dry unit weight: Weight of the solid particles of the soil per unit volume.
Saturated unit weight: Weight of the soil when all voids are filled with water such that no air is present per unit volume. Note that this is typically assumed to occur below the water table.
Porosity 
Ratio of the volume of voids (containing air and/or water) in a soil to the total volume of the soil expressed as a percentage. A porosity of 0% implies that there is neither air nor water in the soil.
Permeability 
A measure of the ability of water to flow through the soil, expressed in units of velocity.
Consolidation 
As a noun, the state of the soil with regards to prior loading conditions; soils can be underconsolidated, normally consolidated or over-consolidated.
As a verb, the process by which water is forced out of a soil matrix due to loading, causing the soil to deform, or decrease in volume, with time.
Soil Settlement 
A decrease in total soil volume concurrent with a decrease in voids.
Shear strength 
Amount of shear force which a soil can resist without failing.
Atterberg Limits 
Liquid limit, plastic limit, and shrinkage limit used in defining other engineering properties of a soil and in soil classification.
Plasticity 
A defining characteristic of soils, most notably clays and silts.

Bulk density a property of particulate materials. ... Cross section showing the water table varying with surface topography as well as a perched water table The water table or phreatic surface is the surface where the water pressure is equal to atmospheric pressure. ... Used in geology, building science and hydrogeology, the porosity of a porous medium (such as rock or sediment) is the proportion of the non-solid volume to the total volume of material, and is defined by the ratio: where Vp is the non-solid volume (pores and liquid) and Vm... Permeability has several meanings: In electromagnetism, permeability is the degree of magnetisation of a material in response to a magnetic field. ... Consolidation is a process by which soils decrease in volume. ... (UTC)Shear strength in geology and geotechnical engineering is a term used to describe the strength of soils, to resist deformation due to shear stress. ... In physics and mechanics, shear refers to a deformation that causes parallel surfaces to slide past one another (as opposed to compression and tension, which cause parallel surfaces to move towards or away from one another). ... The Liquid Limit, also known as the upper plastic limit, and the Atterberg limit, is the water content at which a soil changes from the liquid state to a plastic state. ... The Liquid Limit, also known as the upper plastic limit, and the Atterberg limit, is the water content at which a soil changes from the liquid state to a plastic state. ... The tensile strength of a material is the maximum amount of tensile stress that it can be subjected to before it breaks. ... Soil classification deals with the systematic categorization of soils based on distinguishing characteristics as well as criteria that dictate choices in use. ... Look up plasticity in Wiktionary, the free dictionary. ...

Geotechnical investigation

Geotechnical engineers perform geotechnical investigations to obtain information on the physical properties of soil and rock underlying (and sometimes adjacent to) a site to design earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions. A geotechnical investigation will include surface exploration and subsurface exploration of a site. Sometimes, geophysical methods are used to obtain data about sites. Subsurface exploration usually involves soil sampling and laboratory testing of the soil samples retrieved. Geotechnical engineers perform geotechnical investigations to obtain information on the physical properties of soil and rock underlying (and sometimes adjacent to) a site to design earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions. ... Exploration geophysics is the applied branch of geophysics which uses deep and primarily near surface methods to probe or image the earth. ...


Surface exploration can include Geologic mapping, geophysical methods, and Photogrammetry, or it can be as simple as an engineer walking around on the site to observe the physical conditions at the site. A geologic map is a special-purpose map made for the purpose of showing subsurface geological features. ... Exploration geophysics is the applied branch of geophysics which uses deep and primarily near surface methods to probe or image the earth. ... Photogrammetry is a measurement technology in which the three-dimensional coordinates of points on an object are determined by measurements made in two or more photographic images taken from different positions (see stereoscopy). ...


To obtain information about the soil conditions below the surface, some form of subsurface exploration is required. Methods of observing the soils below the surface, obtaining samples, and determining physical properties of the soils and rock include test pits, trenching (particularly for locating faults and slide planes), borings, and cone penetration tests. Geologic faults, fault lines or simply faults are planar rock fractures, which show evidence of relative movement. ... Landslide of soil and regolith in Pakistan A landslide is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. ... The (Dutch) Cone Penetration Test (CPT) is a test to measure the strength or bearing capacity of (soft) soils. ...


Borings come in two main varieties, large-diameter and small-diameter. Large-diameter borings are rarely used due to safety concerns and expense, but are sometimes used to allow a geologist or engineer to visually and manually examine the soil and rock stratigraphy in-situ. Small-diameter borings are frequently used to allow a geologist or engineer examine soil or rock cuttings from the drilling operation, to retrieve soil samples at depth, and to perform in-place soil tests. A Cone Penetration Test (CPT) is typically performed using an instrumented probe with a conical tip, pushed into the soil hydraulically. A basic CPT instrument reports tip resistance and shear resistance along the cylindrical barrel. CPT data has been correlated to soil properties. Sometimes instruments other than the basic CPT probe are used. The (Dutch) Cone Penetration Test (CPT) is a test to measure the strength or bearing capacity of (soft) soils. ...


Geophysical exploration is also sometimes used; geophysical techniques used for subsurface exploration include measurement of seismic waves (pressure, shear, and Rayleigh waves), using surface-wave methods and/or downhole methods, and electromagnetic surveys (magnetometer, resistivity, and ground-penetrating radar). Exploration geophysics is the applied branch of geophysics which uses deep and primarily near surface methods to probe or image the earth. ... A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. ... Rayleigh waves are a type of surface wave associated on the Earth with earthquakes and subterranean movement of magma. ... A ground-penetrating radar data image, generated as part of the search for the head of Yagan within a grave site in Everton Cemetery in 1997. ...


Soil sampling

Soil samples are obtained in either "disturbed" or "undisturbed" condition; however, "undisturbed" samples are not truly undisturbed. A disturbed sample is one in which the structure of the soil has been changed sufficiently that tests of structural properties of the soil will not be representative of in-situ conditions, and only properties of the soil grains can be accurately determined. An undisturbed sample is one where the condition of the soil in the sample is close enough to the conditions of the soil in-situ to allow tests of structural properties of the soil to be used to approximate the properties of the soil in-situ.


Soil samples are taken using a variety of samplers; some provide only disturbed samples, while others can provide relatively undisturbed samples. Samples can be obtained by methods as simple as digging out soil from the site using a shovel. Samples taken this way are disturbed samples. More sophisticated sampling methods include split-spoon samplers, piston samplers, and pushed samplers. The Standard Penetration Test sampler is a split-spoon sampler, and there are similar samplers with larger sample-barrels. The SPT test returns a sample as well as providing in-situ soil data. SPT samples are disturbed samples, but samples from larger split-spoon samplers can be considered relatively undisturbed. Piston samplers are thin-walled metal tubes which contain a piston at the tip. The samplers are pushed into the bottom of a borehole, with the piston remaining at the surface of the soil while the tube slides past it. These samplers will return undisturbed samples in soft soils, but are difficult to advance in sands and stiff clays, and can be damaged (compromising the sample) if gravel is encountered. The Pitcher Barrel sampler is a direct-push sampler similar to piston samplers, except that there is no piston. There are pressure-relief holes near the top of the sampler to prevent pressure buildup of water or air above the soil sample. Shovel with wide blade - especially appropriate for lifting snow or coal A shovel is a tool for lifting and moving loose material such as coal, gravel, snow, soil, or sand. ... The Standard Penetration Test (SPT) is an in-situ dynamic penetration test designed to provide information on the geotechnical properties of soils. ... Water borehole in northern Uganda A borehole is a deep and narrow shaft in the ground used for abstraction of fluid or gas reserves below the earths surface. ...


Laboratory tests

A wide variety of laboratory tests can be performed on soils to measure a wide variety of soil properties. Some soil properties are intrinsic to the composition of the soil matrix and are not affected by sample disturbance, while other properties depend on the structure of the soil as well as its composition, and can only be effectively tested on relatively undisturbed samples. Some soil tests measure direct properties of the soil, while others measure "index properties" which provide useful information about the soil without directly measuring the property desired.

  • In-situ density. This test requires an undisturbed sample, and measures the bulk density of the soil.
  • Moisture content. This test provides the water content of the soil, normally expressed as a percentage of the weight of water to the dry weight of the soil.
  • Grain Size Analysis using sieves and Hydrometer Tests. These tests are performed on dried soils and do not require undisturbed samples, and determine the distribution of grain sizes within the soil sample.
  • Atterberg Limits (ASTM D4318). These tests determine the moisture contents at which the portion of the soil smaller than 2 mm grain size transitions from a brittle solid to a plastic solid, and from a plastic solid to a viscous liquid. The results are called the Plastic Limit and the Liquid Limit, respectively. The Plasticity Index is the difference between the Liquid Limit and Plastic Limit, and is the range of moisture contents over which the soil acts as a plastic solid. Atterberg Limits tests are used to determine whether the soil will act primarily as a silt or a clay, and whether it is considered "highly plastic".
  • Expansion Index Test. This test uses a remolded sample of the soil to estimate the amount of expansion which can be expected in expansive soils due to changes in moisture content.
  • Direct Shear Test (ASTM D3080)
  • Unconfined Compression (UC) (ASTM D2166)
  • Triaxial Shear Tests
    • CD - Consolidated drained
    • CU - Consolidated undrained (ASTM D4647)
    • UU - Unconsolidated undrained (ASTM D2850)
  • Oedometer Test - including consolidation (ASTM D2435) and swell tests (ASTM D4546)
  • Soil Suction Tests (ASTM D5298)
  • Compaction Tests - Standard Proctor (ASTM D698), Modified Proctor (ASTM D1557), and California Test 216. These tests are used to determine the maximum bulk density to which a soil can be compacted given a specified compaction energy. The soil sample is divided into parts, where each part is brought to a different moisture content through adding water or drying, and compacted into a mold using a specified number of blows of a hammer of standard size and weight falling through a specified distance. The density obtained varies with different moisture contents; the "maximum density" is the highest obtained at any moisture content, while the "optimum moisture" is the moisture content at which the maximum density is obtained. This test is used primarily for providing field control for earthwork, where typical specifications will require that soil be compacted to at least a certain percentage of the maximum density obtained in a compaction test.
  • California Bearing Ratio (ASTM D1883) Test. This test measures the response of a compacted sample of soil or aggregate to a bearing pressure, and is used primarily for the design of pavement sections. This test was developed by CalTrans, but is no longer used in the CalTrans pavement design method. It is still used by other agencies as a cheap method to estimate resilient modulus.
  • R-Value Test. (California Test 301) This test measures the lateral response of a compacted sample of soil or aggregate to a vertically applied pressure under specific conditions. This test is used by CalTrans for pavement design, replacing the California Bearing Ratio test.

A hydrometer is an instrument used for determining the specific gravity of liquids. ... The Liquid Limit, also known as the upper plastic limit, and the Atterberg limit, is the water content at which a soil changes from the liquid state to a plastic state. ... A direct shear test is a laboratory test used by Professional Engineer Mohamed Fazlin to find the shear strength parameters of soil. ... A triaxial shear test is a common method to measure the mechanical properties of many deformable solids, especially soil, sand, clay, and other granular materials or powders. ... Wikipedia does not yet have an article with this exact name. ... Caltrans logo The soaring ramps in the stack interchanges favored by Caltrans often provide stunning views. ... The R-Value test, California Test 301, measures the response of a compacted sample of soil or aggregate to a vertically applied pressure under specific conditions. ... Caltrans logo The soaring ramps in the stack interchanges favored by Caltrans often provide stunning views. ...

Foundations

A building's foundation transmits loads from buildings and other structures to the earth. Geotechnical engineers design foundations based on the load characteristics of the structure and the properties of the soils and/or bedrock at the site. A foundation is a structure that transmits loads from a building or road to the underlying ground. ...


The primary considerations for foundation support are bearing capacity, settlement, and ground movement beneath the foundations. Bearing capacity is the ability of the site soils to support the loads imposed by buildings or structures. Settlement occurs under all foundations in all soil conditions, though lightly loaded structures or rock sites may experience negligible settlements. For heavier structures or softer sites, both overall settlement relative to unbuilt areas or neighboring buildings, and differential settlement under a single structure, can be concerns. Of particular concern is settlement which occurs over time, as immediate settlement can usually be compensated for during construction. Ground movement beneath a structure's foundations can occur due to shrinkage or swell of expansive soils due to climactic changes, frost expansion of soil, melting of permafrost, slope instability, or other causes. All these factors must be considered during design of foundations. In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground. ...


Many building codes specify basic foundation design parameters for simple conditions, frequently varying by jurisdiction, but such design techniques are normally limited to certain types of construction and certain types of sites, and are frequently very conservative.


In areas of shallow bedrock, most foundations may bear directly on bedrock; in other areas, the soil may provide sufficient strength for the support of structures. In areas of deeper bedrock with soft overlying soils, deep foundations are used to support structures directly on the bedrock; in areas where bedrock is not economically available, stiff "bearing layers" are used to support deep foundations instead.


Shallow foundations

Example of a slab-on-grade foundation.
Example of a slab-on-grade foundation.

Image File history File linksMetadata Size of this preview: 800 × 600 pixel Image in higher resolution (1600 × 1200 pixel, file size: 458 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Geotechnical engineering Shallow... Image File history File linksMetadata Size of this preview: 800 × 600 pixel Image in higher resolution (1600 × 1200 pixel, file size: 458 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Geotechnical engineering Shallow...

Footings

Footings (often called "spread footings" because they spread the load) are structural elements which transfer structure loads to the ground by direct areal contact. Footings can be isolated footings for point or column loads, or strip footings for wall or other long (line) loads. Footings are normally constructed from reinforced concrete cast directly onto the soil, and are typically embedded into the ground to penetrate through the zone of frost movement and/or to obtain additional bearing capacity. Reinforced concrete at Sainte Jeanne dArc Church (Nice, France): architect Jacques Dror, 1926–1933 Reinforced concrete, also called ferroconcrete in some countries, is concrete in which reinforcement bars (rebars) or fibers have been incorporated to strengthen a material that would otherwise be brittle. ...


Slab foundations

A variant on spread footings is to have the entire structure bear on a single slab of concrete underlying the entire area of the structure. Slabs must be thick enough to provide sufficient rigidity to spread the bearing loads somewhat uniformly, and to minimize differential settlement across the foundation. In some cases, flexure is allowed and the building is constructed to tolerate small movements of the foundation instead. For small structures, like single-family houses, the slab may be less than 30cm thick; for larger structures, the foundation slab may be several meters thick.


Slab foundations can be either slab-on-grade foundations or embedded foundations, typically in buildings with basements. Slab-on-grade foundations must be designed to allow for potential ground movement due to changing soil conditions. Example of slab on grade foundation Slab-on-grade foundations are a building 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. ...


Deep foundations

Main article: Deep foundations

Deep foundations are used for structures or heavy loads when shallow foundations can not provide adequate capacity, due to size and structural limitations. They may also be used to circumvent weak or compressible soil layers. There are many types of deep foundations including piles, drilled shafts, caissons, piers, and earth stabilized columns. Image File history File linksMetadata Download high-resolution version (600x800, 82 KB) Piledriving at the Maxwell Bridge (Imola Avenue) in Napa, California. ... Image File history File linksMetadata Download high-resolution version (600x800, 82 KB) Piledriving at the Maxwell Bridge (Imola Avenue) in Napa, California. ... Pneumatic crane working as a pile driver The pile driver or piledriver is a term used to describe a mechanical device which converts potential energy into kinetic energy (both forms of mechanical energy). ... Napa is the county seat of Napa County, California. ... Deep foundations are foundations for structures and/or other heavy loads that circumvent weak or compressible soil layers to provide adequate support for the aforementioned structures or loads. ... Look up Pile in Wiktionary, the free dictionary. ...


Lateral earth support structures

Main article: Retaining wall

A retaining wall is a structure that holds back earth. Retaining walls stabilize soil and rock from downslope movement or erosion and provide support for vertical or near-vertical grade changes. Cofferdams and bulkheads, structures to hold back water, are sometimes also considered retaining walls. Structure in the foreground is called a mud box - a kind of retaining wall built to hold the flood waters in check. ...


The primary geotechnical concern in design and installation of retaining walls is that the retained material is attempting to move forward and downslope due to gravity. This creates soil pressure behind the wall, which can be analysed based on the angle of internal friction (φ) and the cohesive strength (c) of the material and the amount of allowable movement of the wall. This pressure is smallest at the top and increases toward the bottom in a manner similar to hydraulic pressure, and tends to push the wall forward and overturn it. Groundwater behind the wall that is not dissipated by a drainage system causes an additional horizontal hydraulic pressure on the wall. Lateral earth pressure theory is the theory predicting the amount of pressure soil can exert perpendicular to gravity. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of geologic formations. ...


Gravity Walls

Gravity walls depend on the size and weight of the wall mass to resist pressures from behind. Gravity walls will often have a slight setback, or batter, to improve wall stability. For short, landscaping walls, gravity walls made from dry-stacked (mortarless) stone or segmental concrete units (masonry units) are commonly used.


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 steel-reinforced backfill soil 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).


For reinforced-soil gravity walls, the soil reinforcement is placed in horizontal layers throughout the height of the wall. Commonly, the soil reinforcement is geogrid, a high-strength polymer mesh, that provide tensile strength to hold soil together. The wall face is often of precast, segmental concrete units that can tolerate some differential movement. The reinforced soil's mass, along with the facing, becomes the 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 (thick) as the height of the wall, and may have to be larger if there is a slope or surcharge on the wall.


Cantilever walls

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 buttressed 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.


Cantilever walls resist lateral pressures by friction at the base of the wall and/or passive earth pressure, the tendency of the soil to resist lateral movement.


Basements are a form of cantilever walls, but the forces on the basement walls are greater than on conventional walls because the basement wall is not free to move.


Excavation shoring

Shoring of temporary excavations frequently requires a wall design which does not extend laterally beyond the wall, so shoring extends below the planned base of the excavation. Common methods of shoring are the use of sheet piles or soldier beams and lagging. Sheet piles are a form of driven piling using thin interlocking sheets of steel to obtain a continuous barrier in the ground, and are driven prior to excavation. Soldier beams are constructed of wide flange steel H sections spaced about 2-3 m apart, driven prior to excavation. As the excavation proceeds, horizontal timber or steel sheeting (lagging) is inserted behind the H pile flanges.


In some cases, the lateral support which can be provided by the shoring wall alone is insufficient to resist the planned lateral loads; in this case additional support is provided by walers or tie-backs. Walers are strutural elements which connect across the excavation so that the loads from the soil on either side of the excavation are used to resist each other, or which transfer horizontal loads from the shoring wall to the base of the excavation. Tie-backs are steel tendons drilled into the face of the wall which extend beyond the soil which is applying pressure to the wall, to provide additional lateral resistance to the wall.


Earth structures

  • Pavements
  • Embankments
  • Reservoirs
  • Engineered Slopes

Slope stability

Simple slope slip section.
Simple slope slip section.
Main article: Slope stability

Slope stability is the analysis of soil covered slopes and its potential to undergo movement. Stability is determined by the balance of shear stress and shear strength. A previously stable slope may be initially affected by preparatory factors, making the slope conditionally unstable. Triggering factors of a slope failure can be climatic events can then make a slope actively unstable, leading to mass movements. Mass movements can be caused by increases in shear stress, such as loading, lateral pressure, and transient forces. Alternatively, shear strength may be decreased by weathering, changes in pore water pressure, and organic material. Image File history File links Download high-resolution version (1170x878, 41 KB) created with Art of Illusion File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high-resolution version (1170x878, 41 KB) created with Art of Illusion File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Figure 1: Simple slope slip section The field of slope stability encompasses the analysis of static and dynamic stability of slopes of earth and rock-fill dams, slopes of other types of embankments, excavated slopes, and natural slopes in soil and soft rock. ... Mass wasting, also known as mass movement or slope movement, is the geomorphic process by which soil, regolith, and rock move downslope under the force of gravity. ... Shear stress is a stress state where the stress is parallel to a face of the material, as opposed to normal stress when the stress is perpendicular to the face. ... (UTC)Shear strength in geology and geotechnical engineering is a term used to describe the strength of soils, to resist deformation due to shear stress. ... Rockslide redirects here. ...


Geosynthetics

A collage of geosynthetic products.
A collage of geosynthetic products.
Main article: Geosynthetics

Geosynthetics is the umbrella term used to describe a range of synthethic products used to aid in solving some geotechnical problems. The term is generally regarded to encompass four main products; geotextiles, geogrids, geomembranes, and geocomposites. The synthetic nature of the products make them suitable for use in the ground where high levels of durability are required, this is not to say that they are indestructible. Geosynthetics are available in a wide range of forms and materials, each to suit a slightly different end use. These products have a wide range of applications and are currently used in many civil and geotechnical engineering applications including roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, landfills, bank protection and coastal engineering Image File history File links Geocollage. ... Image File history File links Geocollage. ... Geosynthetics in use Geosynthetics is the umbrella term used to describe a range of generally synthetic products used to solve geotechnical problems. ... Geosynthetics in use Geosynthetics is the umbrella term used to describe a range of generally synthetic products used to solve geotechnical problems. ...


See also

Soil mechanics is a discipline that applies the principles of engineering mechanics to soil to predict the mechanical behavior of soil. ... The Falkirk Wheel in Scotland. ... In civil engineering, earthworks are engineering works created through the moving of massive quantities of soil or unformed stone. ... Effective stress (σ) is a value reflecting the strength of a soil. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... Engineering Geology is the application of the science of geology to the understanding of geologic phenomena and the engineering solution of geologic hazards and other geologic problems for society. ... // Foundations Principles of Geology Author: Charles Lyell Publication data: 1830–1833. ... In geotechnical engineering, the first major rock mass classification system was proposed about 60 years ago for tunnelling with steel support. ... Seismology (from the Greek seismos = earthquake and logos = word) is the scientific study of earthquakes and the propagation of elastic waves through the Earth. ... Geotechnical engineers perform geotechnical investigations to obtain information on the physical properties of soil and rock underlying (and sometimes adjacent to) a site to design earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions. ... Albury landfill, Surrey, England A landfill, also known as a dump (US) or a tip (UK), is a site for the disposal of waste materials by burial and is the oldest form of waste treatment. ... Land reclamation is either of two distinct practices. ... LIMS Laboratory Instruments Management Systems A set of software tools and hardware used to manage and progress laboratory tests Usually support the laboratory workflows and integration with analyitycal instrumentation for data capturing and acquisition This article is being considered for deletion in accordance with Wikipedias deletion policy. ... Soil physics deals with the physics of soil systems. ... Soil science deals with soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils per se; and these properties in relation to the use and management of soils. ... Look up Pile in Wiktionary, the free dictionary. ... Structure in the foreground is called a mud box - a kind of retaining wall built to hold the flood waters in check. ...

Notes and References

  1. ^ Soil Mechanics, Lambe,T.William and Whitman,Robert V., Massachusetts Institute of Technology, John Wiley & Sons., 1969.
  2. ^ Licensure for Engineers. Retrieved on 2006-12-11.
  • Holtz, R. and Kovacs, W. (1981), An Introduction to Geotechnical Engineering, Prentice-Hall, Inc. ISBN 0-13-484394-0
  • Bowles, J. (1988), Foundation Analysis and Design, McGraw-Hill Publishing Company. ISBN 0-07-006776-7
  • Cedergren, Harry R. (1977), Seepage, Drainage, and Flow Nets, Wiley. ISBN 0-471-14179-8
  • Kramer, Steven L. (1996), Geotechnical Earthquake Engineering, Prentice-Hall, Inc. ISBN 0-13-374943-6
  • Freeze, R.A. & Cherry, J.A., (1979), Groundwater, Prentice-Hall. ISBN 0-13-365312-9
  • Mitchell, James K. & Soga, K. (2005), Fundamentals of Soil Behavior 3rd ed., John Wiley & Sons, Inc.
  • Fang, H.-Y. and Daniels, J. (2005) Introductory Geotechnical Engineering : an environmental perspective, Taylor & Francis. ISBN 0-415-30402-4
  • NAVFAC (Naval Facilities Engineering Command) (1986) Design Manual 7.01, Soil Mechanics, US Government Printing Office
  • NAVFAC (Naval Facilities Engineering Command) (1986) Design Manual 7.02, Foundations and Earth Structures, US Government Printing Office
  • NAVFAC (Naval Facilities Engineering Command) (1983) Design Manual 7.03, Soil Dynamics, Deep Stabilization and Special Geotechnical Construction, US Government Printing Office
  • Terzaghi, K., Peck, R.B. and Mesri, G. (1996), Soil Mechanics in Engineering Practice 3rd Ed., John Wiley & Sons, Inc.

  Results from FactBites:
 
Geotechnical engineering - Wikipedia, the free encyclopedia (316 words)
Geotechnical engineers investigate the soil and bedrock below a site to confirm their engineering properties as they will relate to the proposed costruction.
Geotechnical engineers also assess the risk to humans, property and the environment from natural hazards such as earthquakes, landslides, sinkholes, debris flows, and rock falls (all involving natural materials).
Geotechnical Engineering is also applicable to coastal and ocean engineering applications, such as construction of wharves, marinas, jetties, as well as foundation/anchor systems for offshore structures such as oil platforms.
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m