Английская Википедия:Gravel
Шаблон:Short description Шаблон:Other uses Шаблон:Use dmy dates
Gravel (Шаблон:IPAc-en) is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentary and erosive geological processes; it is also produced in large quantities commercially as crushed stone.
Gravel is classified by particle size range and includes size classes from granule- to boulder-sized fragments. In the Udden-Wentworth scale gravel is categorized into granular gravel (Шаблон:Cvt) and pebble gravel (Шаблон:Cvt). ISO 14688 grades gravels as fine, medium, and coarse, with ranges Шаблон:Cvt for fine and Шаблон:Cvt for coarse. One cubic metre of gravel typically weighs about Шаблон:Cvt, or one cubic yard weighs about Шаблон:Cvt.
Gravel is an important commercial product, with a number of applications. Almost half of all gravel production is used as aggregate for concrete. Much of the rest is used for road construction, either in the road base or as the road surface (with or without asphalt or other binders.) Naturally occurring porous gravel deposits have a high hydraulic conductivity, making them important aquifers.
Definition and properties
Colloquially, the term gravel is often used to describe a mixture of different size pieces of stone mixed with sand and possibly some clay.[1] The American construction industry distinguishes between gravel (a natural material) and crushed stone (produced artificially by mechanical crushing of rock.)[2][3][4]
The technical definition of gravel varies by region and by area of application. Many geologists define gravel simply as loose rounded rock particles over Шаблон:Cvt in diameter, without specifying an upper size limit.[5][6][7][8] Gravel is sometimes distinguished from rubble, which is loose rock particles in the same size range but angular in shape.[9] The Udden-Wentworth scale, widely used by geologists in the US, defines granular gravel as particles with a size from Шаблон:Cvt and pebble gravel as particles with a size from Шаблон:Cvt. This corresponds to all particles with sizes between coarse sand and cobbles.[10]
The U.S. Department of Agriculture and the Soil Science Society of America define gravel as particles from Шаблон:Cvt in size, while the German scale (Atterburg) defines gravel as particles from Шаблон:Cvt in size.[11] The U.S. Army Corps of Engineers defines gravel as particles under Шаблон:Cvt in size that are retained by a number 4 mesh, which has a mesh spacing of Шаблон:Cvt.[12][5] ISO 14688 for soil engineering grades gravels as fine, medium, and coarse with ranges 2 mm to 6.3 mm to 20 mm to 63 mm.[13]
The bulk density of gravel varies from Шаблон:Cvt.[14] Natural gravel has a high hydraulic conductivity, sometimes reaching above 1 cm/s.[15]
Origin
Most gravel is derived from disintegration of bedrock as it weathers. Quartz is the most common mineral found in gravel, as it is hard, chemically inert, and lacks cleavage planes along which the rock easily splits. Most gravel particles consist of multiple mineral grains, since few rocks have mineral grains coarser than about Шаблон:Convert in size. Exceptions include quartz veins, pegmatites, deep intrusions, and high-grade metamorphic rock. The rock fragments are rapidly rounded as they are transported by rivers, often within a few tens of kilometers of their source outcrops.Шаблон:Sfn
Gravel is deposited as gravel blankets or bars in stream channels;Шаблон:Sfn in alluvial fans;[16] in near-shore marine settings, where the gravel is supplied by streams or erosion along the coast;[17][18]Шаблон:Sfn and in the deltas of swift-flowing streams.[19] The upper Mississippi embayment contains extensive chert gravels thought to have their origin less than Шаблон:Convert from the periphery of the embayment.[20]
It has been suggested that wind-formed (aeolian) gravel "megaripples" in Argentina have counterparts on the planet Mars.[21]
Production and uses
Gravel is a major basic raw material ·in construction.[22] Sand is not usually distinguished from gravel in official statistics, but crushed stone is treated as a separate category. In 2020, sand and gravel together made up 23% of all industrial mineral production in the U.S., with a total value of about $12.6 billion. Some 960 million tons of construction sand and gravel were produced. This greatly exceeds production of industrial sand and gravel (68 million tons), which is mostly sand rather than gravel.[23]
It is estimated that almost half of construction sand and gravel is used as aggregate for concrete. Other important uses include in road construction, as road base or in blacktop; as construction fill; and in myriad minor uses.[22]
Gravel is widely and plentifully distributed, mostly as river deposits, river flood plains, and glacial deposits, so that environmental considerations and quality dictate whether alternatives, such as crushed stone, are more economical. Crushed stone is already displacing natural gravel in the eastern United States, and recycled gravel is also becoming increasingly important.[23]
Etymology
The word gravel comes from the Old French gravele[24] or gravelle.[25]
Types
Different varieties of gravel are distinguished by their composition, origin, and use cases. Types of gravel include:
- Bank gravel
- naturally deposited gravel intermixed with sand or clay found in and next to rivers and streams. Also known as "bank run" or "river run".Шаблон:Sfn
- Bench gravel
- a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level. The term is most commonly used in Alaska and the Yukon Territory.Шаблон:Sfn
- Crushed stone
- rock crushed and graded by screens and then mixed to a blend of stones and fines. It is widely used as a surfacing for roads and driveways, sometimes with tar applied over it. Crushed stone may be made from granite, limestone, dolomite, and other rocks. Also known as "crusher run", DGA (dense grade aggregate) QP (quarry process), and shoulder stone.[26] Crushed stone is distinguished from gravel by the U.S. Geological Survey.[23]
- Fine gravel
- gravel consisting of particles with a diameter of Шаблон:Convert[13]
- Lag gravel
- a surface accumulation of coarse gravel produced by the removal of finer particles.
- Pay gravel
- also known as "pay dirt"; a nickname for gravel with a high concentration of gold and other precious metals. The metals are recovered through gold panning.
- Pea gravel
- also known as "pea shingle" is clean gravel similar in size to garden peas.Шаблон:Sfn Used for concrete surfaces, walkways, driveways and as a substrate in home aquariums.
- Piedmont gravel
- a coarse gravel carried down from high places by mountain streams and deposited on relatively flat ground, where the water runs more slowly.Шаблон:Sfn
- Plateau gravel
- a layer of gravel on a plateau or other region above the height at which stream-terrace gravel is usually found.Шаблон:Sfn
- Shingle
- Coarse, loose, well-rounded, waterworn, specifically alluvial and beach, sediment that is largely composed of smooth and spheroidal or flattened pebbles, cobbles, and sometimes small boulders, generally measuring Шаблон:Convert in diameter.Шаблон:Sfn
Relationship to plant life
In locales where gravelly soil is predominant, plant life is generally more sparse.[27] This is due to the inferior ability of gravels to retain moisture, as well as the corresponding paucity of mineral nutrients, since finer soils that contain such minerals are present in smaller amounts.
In the geologic record
Sediments containing over 30% gravel that become lithified into solid rock are termed conglomerate.[6] Conglomerates are widely distributed in sedimentary rock of all ages, but usually as a minor component, making up less than 1% of all sedimentary rock.[7] Alluvial fans likely contain the largest accumulations of gravel in the geologic record.[16] These include conglomerates of the Triassic basins of eastern North America and the New Red Sandstone of south Devon.[12]
See also
References
External links
Шаблон:Commons category-inline
- Шаблон:Cite EB1911
- British Geological Survey UKGravelBarriers: Understanding coastal protection by gravel barriers in a changing climate
Шаблон:Geotechnical engineering Шаблон:Authority control
- ↑ Шаблон:Cite OED
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite web
- ↑ Шаблон:Cite web
- ↑ 5,0 5,1 Шаблон:Cite book
- ↑ 6,0 6,1 Шаблон:Cite book
- ↑ 7,0 7,1 Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite book
- ↑ 12,0 12,1 Шаблон:Cite book
- ↑ 13,0 13,1 Шаблон:Cite web
- ↑ Шаблон:Cite book
- ↑ Шаблон:Cite book
- ↑ 16,0 16,1 Шаблон:Cite book
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ Шаблон:Cite journal
- ↑ 22,0 22,1 Шаблон:Cite journal
- ↑ 23,0 23,1 23,2 Шаблон:Cite report
- ↑ Collins English Dictionary – Complete & Unabridged 11th Edition. Retrieved 30 August 2012 from CollinsDictionary.com website:http://www.collinsdictionary.com/dictionary/english/gravel
- ↑ Gravel, n., Oxford English Dictionary Second Edition on CD-ROM (v. 4.0) © Oxford University Press 2009
- ↑ Шаблон:Cite web
- ↑ C.Michael Hogan. 2010. Abiotic factor. Encyclopedia of Earth. eds Emily Monosson and C. Cleveland. National Council for Science and the Environment Шаблон:Webarchive. Washington DC
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