Soil compaction

In geotechnical engineering, soil compaction is the process in which a stress applied to a soil causes densification as air is displaced from the pores between the soil grains. When stress is applied that causes densification due to water (or other liquid) being displaced from between the soil grains, then consolidation, not compaction, has occurred. Normally, compaction is the result of heavy machinery compressing the soil, but it can also occur due to the passage of (e.g.) animal feet.

In soil science and agronomy, soil compaction is usually a combination of both engineering compaction and consolidation, so may occur due to a lack of water in the soil, the applied stress being internal suction due to water evaporation[1] as well as due to passage of animal feet. Affected soils become less able to absorb rainfall, thus increasing runoff and erosion. Plants have difficulty in compacted soil because the mineral grains are pressed together, leaving little space for air and water, which are essential for root growth. Burrowing animals also find it a hostile environment, because the denser soil is more difficult to penetrate. The ability of a soil to recover from this type of compaction depends on climate, mineralogy and fauna. Soils with high shrink-swell capacity, such as vertisols, recover quickly from compaction where moisture conditions are variable (dry spells shrink the soil, causing it to crack). But clays which do not crack as they dry cannot recover from compaction on their own unless they host ground-dwelling animals such as earthworms — the Cecil soil series is an example.

CaseCrawlerWithTamper3658
A crawler-backhoe is here equipped with a narrow sheepsfoot roller to compact the fill over newly placed sewer pipe, forming a stable support for a new road surface.
Seabees compactor roller
A compactor/roller fitted with a sheepsfoot drum, operated by U.S. Navy Seabees.
Hamm 3307
A Hamm vibrating roller with plain drum as used for compacting asphalt and granular soils.
Wacker Neuson Stampfer BS 60-2i
Wacker Neuson vibratory rammer BS 60-2i in action.

In construction

Soil compaction is a vital part of the construction process. It is used for support of structural entities such as building foundations, roadways, walkways, and earth retaining structures to name a few. For a given soil type certain properties may deem it more or less desirable to perform adequately for a particular circumstance. In general, the preselected soil should have adequate strength, be relatively incompressible so that future settlement is not significant, be stable against volume change as water content or other factors vary, be durable and safe against deterioration, and possess proper permeability.[2]

When an area is to be filled or backfilled the soil is placed in layers called lifts. The ability of the first fill layers to be properly compacted will depend on the condition of the natural material being covered. If unsuitable material is left in place and backfilled, it may compress over a long period under the weight of the earth fill, causing settlement cracks in the fill or in any structure supported by the fill.[3] In order to determine if the natural soil will support the first fill layers, an area can be proofrolled. Proofrolling consists of utilizing a piece heavy construction equipment (typically, heavy compaction equipment or hauling equipment) to roll across the fill site and watching for deflections to be revealed. These areas will be indicated by the development of rutting, pumping, or ground weaving.[4]

To ensure adequate soil compaction is achieved, project specifications will indicate the required soil density or degree of compaction that must be achieved. These specifications are generally recommended by a geotechnical engineer in a geotechnical engineering report.

The soil type - that is, grain-size distributions, shape of the soil grains, specific gravity of soil solids, and amount and type of clay minerals, present - has a great influence on the maximum dry unit weight and optimum moisture content.[5] It also has a great influence on how the materials should be compacted in given situations. Compaction is accomplished by use of heavy equipment. In sands and gravels, the equipment usually vibrates, to cause re-orientation of the soil particles into a denser configuration. In silts and clays, a sheepsfoot roller is frequently used, to create small zones of intense shearing, which drives air out of the soil.

Determination of adequate compaction is done by determining the in-situ density of the soil and comparing it to the maximum density determined by a laboratory test. The most commonly used laboratory test is called the Proctor compaction test and there are two different methods in obtaining the maximum density. They are the standard Proctor and modified Proctor tests; the modified Proctor is more commonly used. For small dams, the standard Proctor may still be the reference.[4]

While soil under structures and pavements needs to be compacted, it is important after construction to decompact areas to be landscaped so that vegetation can grow.

Compaction methods

There are several means of achieving compaction of a material. Some are more appropriate for soil compaction than others, while some techniques are only suitable for particular soils or soils in particular conditions. Some are more suited to compaction of non-soil materials such as asphalt. Generally, those that can apply significant amounts of shear as well as compressive stress, are most effective.

The available techniques can be classified as:

  1. Static - a large stress is slowly applied to the soil and then released.
  2. Impact - the stress is applied by dropping a large mass onto the surface of the soil.
  3. Vibrating - a stress is applied repeatedly and rapidly via a mechanically driven plate or hammer. Often combined with rolling compaction (see below).
  4. Gyrating - a static stress is applied and maintained in one direction while the soil is a subjected to a gyratory motion about the axis of static loading. Limited to laboratory applications.
  5. Rolling - a heavy cylinder is rolled over the surface of the soil. Commonly used on sports pitches. Roller-compactors are often fitted with vibratory devices to enhance their effectiveness.
  6. Kneading - shear is applied by alternating movement in adjacent positions. An example, combined with rolling compaction, is the 'sheepsfoot' roller used in waste compaction at landfills.

The construction plant available to achieve compaction is extremely varied and is described elsewhere.

Test methods in laboratory

Soil compactors are used to perform test methods which cover laboratory compaction methods used to determine the relationship between molding water content and dry unit weight of soils. Soil placed as engineering fill is compacted to a dense state to obtain satisfactory engineering properties such as, shear strength, compressibility, or permeability. In addition, foundation soils are often compacted to improve their engineering properties. Laboratory compaction tests provide the basis for determining the percent compaction and molding water content needed to achieve the required engineering properties, and for controlling construction to assure that the required compaction and water contents are achieved. Test methods such as EN 13286-2, EN 13286-47, ASTM D698, ASTM D1557, AASHTO T99, AASHTO T180, AASHTO T193, BS 1377:4 provide soil compaction testing procedures.[6]

See also

References

  1. ^ Soil compaction due to lack of water in soil
  2. ^ McCarthy, David F. (2007). Essentials of Soil Mechanics and Foundations. Upper Saddle River, NJ: Pearson Prentice Hall. p. 595. ISBN 0-13-114560-6.
  3. ^ McCarthy, David F. (2007). Essentials of Soil Mechanics and Foundations. Upper Saddle River, NJ: Pearson Prentice Hall. pp. 601–602. ISBN 0-13-114560-6.
  4. ^ a b McCarthy, David F. (2007). Essentials of Soil Mechanics and Foundations. Upper Saddle River, NJ: Pearson Prentice Hall. p. 602. ISBN 0-13-114560-6.
  5. ^ Das, Braja M. (2002). Principles of Geotechnical Engineering. Pacific Grove, CA: Brooks/Cole. p. 105. ISBN 0-534-38742-X.
  6. ^ "Automatic Soil Compactor". http://cooper.co.uk. Cooper Research Technology. Retrieved 8 September 2014. External link in |website= (help)
Carabus problematicus

Carabus problematicus is a species of beetle endemic to Europe, where it is observed in Andorra, Austria, Belgium, Great Britain, the Czech Republic, mainland Denmark, the Faroe Islands, Finland, mainland France, Germany, Hungary, Iceland, Ireland, mainland Italy, Latvia (doubtful), Liechtenstein, Luxembourg, mainland Norway, Poland, Romania, northern and northwestern Russia, Slovakia, Slovenia, mainland Spain, Sweden, Switzerland, and the Netherlands.

A study of the effects of grazing management on arthropod distribution observed high number clusters of C. problematicus associated with the sheep rather than sheep and cattle grazed plots – suggesting that there are detrimental effects of cattle to the species; possibly as a result of soil compaction.

Cecil (soil)

Originally mapped in Cecil County, Maryland in 1899, more than 10 million acres (40,000 km²) of the Cecil soil series (Fine, kaolinitic, thermic Typic Kanhapludults) are now mapped in the Piedmont region of the southeastern United States. It extends from Virginia through North Carolina (where it is the state soil), South Carolina, Georgia and Alabama, with the typic Cecil pedon actually located in Franklin County, NC. A map showing the actual extent of the Cecil series is available at the Center for Environmental Informatics

The Cecil series developed over igneous rock such as granite, and metamorphic rock which is chemically similar to granite. Virgin Cecil soils support forests dominated by pine, oak and hickory, and have a topsoil of brown sandy loam. The subsoil is a red clay which is dominated by kaolinite and has considerable mica. Few Cecil soils are in their virgin state, for most have been cultivated at one time or another. Indifferent land management has allowed many areas of Cecil soils to lose their topsoils through soil erosion, exposing the red clay subsoil. This clay is amenable to cultivation, responds well to careful management, and supports good growth of pine where allowed to revert to forest. Like other well-drained Ultisols, it is ideal for urban development; however, in common with other kaolinite-dominated clays, it has little ability to recover from soil compaction. Total potassium in the Cecil is higher than typical for Ultisols due to the presence of mica.

Colloid-facilitated transport

Colloid-facilitated transport designates a transport process by which colloidal particles serve as transport vector

of diverse contaminants in the surface water (sea water, lakes, rivers, fresh water bodies) and in underground water circulating in fissured rocks

(limestone, sandstone, granite, ...). The transport of colloidal particles in surface soils and in the ground can also occur, depending on the soil structure, soil compaction, and the particles size, but the importance of colloidal transport was only given sufficient attention during the 1980 years.

Radionuclides, heavy metals, and organic pollutants, easily sorb onto colloids suspended in water and that can easily act as contaminant carrier.

Various types of colloids are recognised: inorganic colloids (clay particles, silicates, iron oxy-hydroxides, ...), organic colloids (humic and fulvic substances). When heavy metals or radionuclides form their own pure colloids, the term "Eigencolloid" is used to designate pure phases, e.g., Tc(OH)4, Th(OH)4, U(OH)4, Am(OH)3. Colloids have been suspected for the long range transport of plutonium on the Nevada Nuclear Test Site. They have been the subject of detailed studies for many years. However, the mobility of inorganic colloids is very low in compacted bentonites and in deep clay formations

because of the process of ultrafiltration occurring in dense clay membrane.

The question is less clear for small organic colloids often mixed in porewater with truly dissolved organic molecules.

Compaction

Compaction may refer to:

Soil compaction, for mechanically induced compaction near the ground surface

Compaction (geology), part of the process of lithification involving mechanical dewatering of a sediment by progressive loading under several km of geomaterial

Waste compaction, related to garbage

Cold compaction, powder compaction at low temperatures

Data compaction, related to computers

Curve-fitting compaction

Compactor, a device that performs compaction

Compaction, a cellular differentiation process during early embryogenesis, which occurs during the cleavage stage of human embryogenesis

Consolidation (soil)

In. soil mechanics, consolidation refers to the process by which soil changes volume gradually in response to a change in pressure. This happens because soil is a two-phase material, comprising soil grains and pore fluid, usually groundwater. When soil saturated with water is subject to an increase in pressure, the high volumetric stiffness of water compared to the soil matrix means that the water initially absorbs all the change in pressure without changing volume, creating excess pore water pressure. As water diffuses away from regions of high pressure due to seepage, the soil matrix gradually takes up the pressure change and shrinks in volume. The theoretical framework of consolidation is therefore closely related to the diffusion equation, the concept of effective stress, and hydraulic conductivity.

In the narrow sense, "consolidation" refers strictly to this delayed volumetric response to pressure change due to gradual movement of water. Some publications also use "consolidation" in the broad sense, to refer to any process by which soil changes volume due to a change in applied pressure. This broader definition encompasses the overall concept of soil compaction, subsidence, and heave. Some types of soil, mainly those rich in organic matter, show significant creep, whereby the soil changes volume slowly at constant effective stress over a longer time-scale than consolidation due to the diffusion of water. To distinguish between the two mechanisms, "primary consolidation" refers to consolidation due to dissipation of excess water pressure, while "secondary consolidation" refers to the creep process.

The effects of consolidation are most conspicuous where a building sits over a layer of soil with low stiffness and low permeability, such as marine clay, leading to large settlement over many years. Types of construction project where consolidation often poses technical risk include land reclamation, the construction of embankments, and tunnel and basement excavation in clay.

Geotechnical engineers use oedometers to quantify the effects of consolidation. In an oedometer test, a series of known pressures are applied to a thin disc of soil sample, and the change of sample thickness with time is recorded. This allows the consolidation characteristics of the soil to be quantified in terms of the coefficient of consolidation () and hydraulic conductivity ().

Controlled traffic farming

Controlled traffic farming (CTF) is a management tool which is used to reduce the damage to soils caused by heavy or repeated agricultural machinery passes on the land. This damage and its negative consequences have been well documented and include increased fuel use, poor seedbeds, reduced crop yields and poor soil function in terms of water infiltration, drainage and greenhouse gas mitigation due to soil compaction.Controlled traffic farming is a system which confines all machinery loads to the least possible area of permanent traffic lanes. Current farming systems allow machines to run at random over the land, compacting around 75% of the area within one season and at least the whole area by the second season. Soils don’t recover quickly, taking as much as a few years (e.g., >5 years, particularly in soils without swelling-shrinking properties). A proper CTF system on the other hand can reduce tracking to just 15% and this is always in the same place. CTF is a tool; it does not include a prescription for tillage although most growers adopting CTF use little or none because soil structure does not need to be repaired. The permanent traffic lanes are normally parallel to each other and this is the most efficient way of achieving CTF, but the definition does not preclude tracking at an angle. The permanent traffic lanes may be cropped or non-cropped depending on a wide range of variables and local constraints.

Cultipacker

A cultipacker is a piece of agricultural equipment that crushes dirt clods, removes air pockets, and presses down small stones, forming a smooth, firm seedbed. Where seed has been broadcast, the roller gently firms the soil around the seeds, ensuring shallow seed placement and excellent seed-to-soil contact.

The term cultipacker is almost exclusively applied to ridged rollers, while the terms field roller or land roller may refer to either a smooth or a ridged roller. Some farmers treat the terms as mutually exclusive, but many others treat the ridged tools as a class of field rollers. For example, C.H. Wendel's Encyclopedia of American Farm Implements and Antiques covers the whole category as land rollers. The term cultipacker appeared in English around 1914 and probably originated as a brand name of the C.G. Dunham Company of Berea, Ohio, which advertised "Culti-Packer" models starting around that time. That company did not have the ridged-roller subcategory to itself by any stretch, as Wendel's book demonstrates, but for whatever reason, its name for its version stuck well in many minds. By the 1920s and ever since, it has been widely used in a genericized sense, at least in some regions of the U.S. if not nationwide. In Britain, an equivalent tool is usually called a Cambridge roller or Cambridge roll; D.J. Smith's Discovering Horse-drawn Farm Machinery says, "The Cambridge roll, named after its makers, was a ring roller made up of numerous equally spaced rings or ridges."Despite the suggestion of soil compaction in the "packer" part of the name, cultipackers and other land rollers exert high pressure only on the high spots (such as clods); the baseline pressure at the rest of the footprint is not especially high, which is to say, not higher than a person's footprint pressure. A person intentionally stomping hard on a particular spot can pack the dirt tighter than a cultipacker packs it. This is appropriate because seedbeds need only be firm, not excessively compacted.

Ecoforestry

Ecoforestry has been defined as selection forestry or restoration forestry. The main idea of Ecoforestry is to maintain or restore the forest to standards where the forest may still be harvested for products on a sustainable basis. Ecoforestry is forestry that emphasizes holistic practices which strive to protect and restore ecosystems rather than maximize economic productivity. Sustainability of the forest also comes with uncertainties. There are other factors that may affect the forest furthermore than that of the harvesting. There are internal conditions such as effects of soil compaction, tree damage, disease, fire, and blow down that also directly affect the ecosystem. These factors have to be taken into account when determining the sustainability of a forest. If these factors are added to the harvesting and production that comes out of the forest, then the forest will become less likely to survive, and will then become less sustainable.

Since the forest is considered an ecosystem, it is dependent on all of the living and non-living factors within itself. This is a major part of why the forest needs to be sustainable before it is harvested. For example, a tree, by way of photosynthesis, converts sunlight to sugars for respiration to keep the tree alive. The remains of the converted sugars is left in roots for consumption by the organisms surrounding the tree in the habitat. This shows the productivity of an ecosystem with its inhabitants. Productivity within the ecosystem cannot come to fruition unless the forest is sustainable enough to be harvested. If most individual organisms of the ecosystem vanish, the ecosystem itself is at risk. Once that happens, there is no longer any forest to harvest from. The overall productivity of a system can be found in an equation where the Net Primary Production, or NPP, is equal to the Gross Primary Production, or GPP, minus the Respiration, or R. The formula is the NPP = GPP - R. The NPP is the overall efficiency of the plants in the ecosystem. Through having a constant efficiency in NPP, the ecosystem is then more sustainable. The GPP refers to the rate of energy stored by photosynthesis in plants. The R refers to the maintenance and reproduction of plants from the energy expended.

Ecoforestry has many principles within the existence of itself. It covers sustainable development and the fair harvesting of the organisms living within the forest ecosystem. There have been many proposals of principles outlined for ecoforestry. They are covered over books, articles, and environmental agencies. All of the principles relate to the idea that in ecoforestry, less should be harvested, and diversity must be managed. Through harvesting less, there is enough biomass left in the forest, so that the forest may stay healthy and still stay maintained. It will grow at a sustainable level annually, and thus it will be able to still be harvested the following year. Through management of the diversity, species may cohabitate in an ecosystem where the forest may feed off of other species in its growth and production. The Principles of Ecoforestry may be found below.

Heidemann Bay

Heidemann Bay (68°35′S 77°58′E) is a bay, 1 nautical mile (2 km) long, indenting the seaward end of Breidnes Peninsula in the Vestfold Hills of Antarctica, just south of Davis Station. It was mapped by Norwegian cartographers from air photos taken by the Lars Christensen Expedition, 1936–37. The bay was first visited by an Australian National Antarctic Research Expeditions party from the Kista Dan on January 11, 1957, and was named for Frank Heidemann, second mate of the Kista Dan.

Heidemann Bay which was gouged by glaciers is flanked by two small peninsulas which rise approximately 20 metres above sea level.

Heidemann Bay is an extension of Heidemann Valley which runs in the same compass direction for a further two kilometres. Heidemann Valley is of uniform elevation and relatively flat but covered in a large number of moraine rocks and boulders.

A few hundred metres from Heidemann Bay in Heidemann Valley was the site of the first soil compaction tests in the early 1980s, to determine if it was feasible to construct a dirt runway in that environment.

Suter Island is a small island lying 0.5 miles (0.8 km) southwest of the south entrance point to Heidemann Bay.

Knightwood Oak

The Knightwood Oak is a pedunculate oak and the largest, and perhaps most famous, oak tree in the New Forest, in southern England. It is also known as the Queen of the Forest. It is over 500 years old and has a girth of 7.38 metres (24.2 ft). The tree is still growing. It was pollarded when about 200 years old and is thought to have been last pollarded about 150 years ago.The tree is located about 2.4 miles (3.9 km) WSW of Lyndhurst and just north of the A35 road at grid reference SU265065. There is a car park nearby and a gravel path, suitable for wheelchairs, leads to and around the tree. An interpretative panel explains the tree's history. A fence encircles the tree to protect its roots from soil compaction due to foot traffic. The tree has been popular with visitors for a long time and at the height of its fame, in Victorian times, people would come from far and wide to see it. It is even reputed to have been visited by Henry VIII during a hunting expedition in the forest.

In February 2006, the Forestry Commission harvested twigs from the tree to produce new ‘Knightwood’ oaks with identical genes. Some will be planted near the original tree, while others will go to New Park, near Brockenhurst.

Land development

Land development is altering the landscape in any number of ways such as:

Changing landforms from a natural or semi-natural state for a purpose such as agriculture or housing

Subdividing real estate into lots, typically for the purpose of building homes

Real estate development or changing its purpose, for example by converting an unused factory complex into condominia.

Lawn aerator

A lawn aerator is a garden tool designed to create holes in the soil in order to help lawn grasses grow. In compacted lawns, aeration improves soil drainage and encourages worms, microfauna and microflora which require oxygen.

Lite-Trac

Lite-Trac is a trading name of Holme Farm Supplies Ltd, a manufacturer of agricultural machinery registered in England and based in Peterborough. The Lite-Trac name comes from "lite tractor", due to the patented chassis design enabling the inherently very heavy machines manufactured by the company to have a light footprint for minimum soil compaction.

Holme Farm Supplies Ltd agricultural products, sold under the Lite-Trac name, include tool carriers, self-propelled lime and fertiliser spreaders, sprayers, granular applicators and tank masters. Lite-Trac is currently the manufacturer of Europe's largest four-wheeled self-propelled crop sprayers. The company's products are identifiable by the combination of unpainted stainless steel tanks and booms with bright yellow cabs and detailing.

Midland Cogeneration Venture

The Midland Cogeneration Venture (MCV) is a natural gas-fired electrical and steam co-generation plant in Midland, Michigan owned by Midland Cogeneration Venture Limited Partnership. When it began operation in 1991, it was the largest gas-fired steam recovery power plant in the world.Originally designed as the Midland Nuclear Power Plant, the initial design called for two Babcock & Wilcox pressurized water reactors. Reactor one was designed with a 460 MWe rating, and reactor two with an 808 MWe rating. The design called for once-through steam generators (OTSGs) similar to those at Oconee. Consumers Power abandoned the project, which was 85% complete, in 1984 citing numerous construction problems, most notably a sinking foundation. These problems included sinking and cracking of some buildings on the site due to poor soil compaction prior to construction, as well as shifting regulatory requirements following the 1979 accident at Three Mile Island. Construction was also opposed by environmentalists, led by Midland resident, Mary P. Sinclair.By then, 17 years and US$4.3 billion had been invested in the project. Consumers Power, nearly bankrupted by the project, formed a holding company, CMS Energy for it to be a subsidiary of and eventually changed its name to Consumers Energy.

Conversion of the plant began in 1986 and was completed at a cost of $500 million, almost twice the original estimate of the nuclear facility. First electrical production occurred in 1990. The plant produces 1,560 Megawatts of electricity for Consumers and 1.35 million pounds per hour of industrial steam for Dow Chemical. The electrical capacity is approximately 10% of the power consumption for the lower peninsula of Michigan. Over time the plant capacity was further up-rated to 1,633 Megawatts and 1.5 million pounds per hour steam.

On July 17, 2002, one of the unused 84-ton nuclear reactor vessel heads was removed from its containment building for transportation to Davis-Besse Nuclear Power Station near Toledo, Ohio, where it replaced a damaged vessel head on a reactor built by the same contractor as the Midland units, B&W.

Consumers owned a 49 percent share in MCV until 2006. Eight other companies owned the remaining 51 percent. In mid-December 2012 Midland Cogeneration Venture was purchased by Borealis Infrastructure. In 2013 the Global Strategic Investment Alliance (GSIA) became a 33% investor. In 2017, Borealis Infrastructure was renamed OMERS Infrastructure Management Inc. Peter (Pete) Milojevic, MCV President and CEO since August 2013, has indicated the company is ready to further expand the electricity capacity of the facility by approximately 800 Megawatts to help replace permanent shutdowns of other generating facilities in the state of Michigan. This would increase MCV's total electricity capacity to about 2,400 Megawatts.

Plastic mulch

Plastic mulch is a product used, in a similar fashion to mulch, to suppress weeds and conserve water in crop production and landscaping. Certain plastic mulches also act as a barrier to keep methyl bromide, both a powerful fumigant and ozone depleter, in the soil. Crops grow through slits or holes in thin plastic sheeting. Plastic mulch is often used in conjunction with drip irrigation. Some research has been done using different colors of mulch to affect crop growth. This method is predominant in large-scale vegetable growing, with millions of acres cultivated under plastic mulch worldwide each year. Disposal of plastic mulch is cited as an environmental problem; however, technologies exist to provide for the recycling of used/disposed plastic mulch into viable plastic resins for re-use in the plastics manufacturing industry.

Proctor compaction test

The Proctor compaction test is a laboratory method of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density. The test is named in honor of Ralph R. Proctor, who in 1933 showed that the dry density of a soil for a given compactive effort depends on the amount of water the soil contains during soil compaction. His original test is most commonly referred to as the standard Proctor compaction test; his test was later updated to create the modified Proctor compaction test.

These laboratory tests generally consist of compacting soil at known moisture content into a cylindrical mold of standard dimensions using a compactive effort of controlled magnitude. The soil is usually compacted into the mold to a certain amount of equal layers, each receiving a number of blows from a standard weighted hammer at a specified height. This process is then repeated for various moisture contents and the dry densities are determined for each. The graphical relationship of the dry density to moisture content is then plotted to establish the compaction curve. The maximum dry density is finally obtained from the peak point of the compaction curve and its corresponding moisture content, also known as the optimal moisture content.

The testing described is generally consistent with the American Society for Testing and Materials (ASTM) standards, and are similar to the American Association of State Highway and Transportation Officials (AASHTO) standards. Currently, the procedures and equipment details for the standard Proctor compaction test is designated by ASTM D698 and AASHTO T99. Also, the modified Proctor compaction test is designated by ASTM D1557 and AASHTO T180-D.

Soil compaction (agriculture)

Soil compaction, also known as soil structure degradation, is the increase of bulk density or decrease in porosity of soil due to externally or internally applied loads. Compaction can adversely affect nearly all physical, chemical and biological properties and functions of soil. Together with soil erosion, it is regarded as the "costliest and most serious environmental problem caused by conventional agriculture."In agriculture, soil compaction is a complex problem in which soil, crops, weather and machinery interact. External pressure due to the use of heavy machinery and inappropriate soil management can lead to the compaction of subsoil, creating impermeable layers within the soil that restrict water and nutrient cycles. This process can cause on-site effects such as reduced crop growth, yield and quality as well as off-site effects such as increased surface water run-off, soil erosion, greenhouse gas emissions, eutrophication, reduced groundwater recharge and a loss of biodiversity.Unlike salinization or erosion, soil compaction is principally a sub-surface problem and therefore an invisible phenomenon. Special identification methods are necessary to locate, monitor and manage the problem appropriately.

Top soil compaction is considered partly reversible and its occurrence controllable. Subsoil compaction, however, is regarded as the major problem because it can be permanent, meaning the pore functions can potentially not be restored after deterioration. Since farmers in modern intensive agriculture depend on heavy machinery and therefore cannot completely avoid compaction, soil compaction management approaches focus on mitigation. Attempts to mitigate soil compaction include biological, chemical and technical approaches. Long-term public policies can tackle the underlying reasons for soil compaction. For instance, subsidies for low-tech agriculture may decrease heavy machinery use on the field, and educational programs aiming at slowing population growth can lower the pressure on agriculture caused by population size.

Soil conditioner

A soil conditioner is a product which is added to soil to improve the soil’s physical qualities, usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics. In general usage, the term "soil conditioner" is often thought of as a subset of the category soil amendments (or soil improvement, soil condition), which more often is understood to include a wide range of fertilizers and non-organic materials.Soil conditioners can be used to improve poor soils, or to rebuild soils which have been damaged by improper soil management. They can make poor soils more usable, and can be used to maintain soils in peak condition.

Tree care

Tree care is the application of arboricultural methods like pruning, trimming, and felling/thinning in built environments. Road verge, greenways, backyard and park woody vegetation are at the center of attention for the tree care industry. Landscape architecture and urban forestry also set high demands on professional tree care. High safety standards against the dangers of tree care have helped the industry evolve. Especially felling in space-limited environments poses significant risks: the vicinity of power or telephone lines, insufficient protective gear (against falling dead wood, chainsaw wounds, etc.) and narrow felling zones with endangered nearby buildings, parking cars, etc.. The required equipment and experience usually transcends private means and is often considered too costly as a permanent part of the public infrastructure. In singular cases, traditional tools like handsaws may suffice, but large-scale tree care usually calls for heavy machinery like cranes, bucket trucks,harvesters, and woodchippers.

Road side trees are especially prone to biotic stress by exhaust fumes, toxic road debris, soil compaction, and drought which makes them susceptible to fungal infections and various plant pests. When tree removal is not an option, because of road ecology considerations, the main challenge is to achieve road safety (visibility of road signs, blockage-free lanes, etc.) while maintaining tree health.

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