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Cave-in
A cave-in is a collapse of a geologic formation, mine or structure which may occur during mining, tunneling, or steep-walled excavation such as trenching. Geologic structures prone to spontaneous cave-ins include alvar, tsingy and other limestone formations, but can also include lava tubes and a variety of other subsurface rock formations. Glacier caves and other ice formations are very prone to collapse from exposure to warm temperatures or running water. In mining, the term roof fall is used to refer to many types of collapses, ranging from the fall of a single flake of shale to collapses that form sink holes that reach to the surface. However, roof falls in mining are not all accidental. In longwall mining and retreat mining, miners systematically remove all support from under large areas of the mine roof, allowing it to settle just beyond the work area. The goal in such mining methods is not to prevent roof fall and the ensuing surface subsidence, but rather to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trench
A trench is a type of digging, excavation or depression in the ground that is generally deeper than it is wide (as opposed to a swale (landform), swale or a bar ditch), and narrow compared with its length (as opposed to a simple hole or trapping pit, pit). In geology, trenches result from erosion by rivers or by geological movement of tectonic plates. In civil engineering, trenches are often created to install underground utilities such as Pipeline transport, gas, Water distribution system, water, Underground power lines, power and Undergrounding, communication lines. In construction, trenches are dug for foundations of buildings, retaining walls and dams, and for Tunnel construction#Cut-and-cover, cut-and-cover construction of tunnels. In archaeology, the "trench method" is used for searching and Excavation (archaeology), excavating ancient ruins or to dig into stratum, strata of sedimented material. In geotechnical engineering, trench investigations locate faults and investigat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cave-in (indust)
A cave-in is a collapse of a geologic formation, mine or structure which may occur during mining, tunneling, or steep-walled excavation such as trenching. Geologic structures prone to spontaneous cave-ins include alvar, tsingy and other limestone formations, but can also include lava tubes and a variety of other subsurface rock formations. Glacier caves and other ice formations are very prone to collapse from exposure to warm temperatures or running water. In mining, the term roof fall is used to refer to many types of collapses, ranging from the fall of a single flake of shale to collapses that form sink holes that reach to the surface. However, roof falls in mining are not all accidental. In longwall mining and retreat mining, miners systematically remove all support from under large areas of the mine roof, allowing it to settle just beyond the work area. The goal in such mining methods is not to prevent roof fall and the ensuing surface subsidence, but rather to contro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digging
Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surface, usually soil, sand or rock on the surface of Earth. Digging is actually the combination of two processes, the first being the breaking or cutting of the surface, and the second being the removal and relocation of the material found there.Carl Dreher,The Right Way to Dig, ''Popular Science'' (March 1957), p. 179. In a simple digging situation, this may be accomplished in a single motion, with the digging implement being used to break the surface and immediately fling the material away from the hole or other structure being dug. Many kinds of animals engage in digging, either as part of burrowing behavior or to search for food or water under the surface of the ground.Zen Faulkes,Morphological Adaptations for Digging and Burrowing (2013), p. 276-295. Historically, humans have engaged in digging for both of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Longwall Mining
Longwall mining is a form of underground coal mining where a long wall of coal is mined in a single slice (typically thick). The section of rock that is being mined, known as the longwall panel, is typically long, but can be up to long and wide. The longwall method compares with shortwall, room-and-pillar, and several others. History The basic idea of longwall mining was developed in England in the late 17th century, although it may have been anticipated in the pre-industrial era by a similar technique utilized by the Hopi of Northeastern Arizona in the 14th century. Miners undercut the coal along the width of the coal face, removing coal as it fell, and used wooden props to control the fall of the roof behind the face. This was known as the Shropshire method of mining. While the technology has changed considerably, the basic idea remains the same, to remove essentially all of the coal from a broad coal face and allow the roof and overlying rock to collapse into the void be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Madagascar Dry Deciduous Forests
The Madagascar dry deciduous forests represent a tropical and subtropical dry broadleaf forests, tropical dry forest ecoregion situated in the western and northern part of Madagascar. The area has high numbers of Endemism, endemic plant and animal species but has suffered large-scale clearance for agriculture. They are among the world's richest and most distinctive dry forests and included in the Global 200 ecoregions by the World Wide Fund for Nature, World Wide Fund. The area is also home to distinctive limestone karst formations known as Karst topography, tsingy, including the World Heritage Site of Tsingy de Bemaraha Strict Nature Reserve, Bemaraha. Geography There are two separate areas within the ecoregion: the western side of Madagascar from the Ampasindava peninsula in the north to Belo-sur-Tsiribihina and Maromandia in the south (this is most of Mahajanga Province); and the northern tip of the island (apart from the high areas of Amber Mountain National Park, Amber Mount ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sweden
Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic country by both area and population, and is the List of European countries by area, fifth-largest country in Europe. Its capital and largest city is Stockholm. Sweden has a population of 10.6 million, and a low population density of ; 88% of Swedes reside in urban areas. They are mostly in the central and southern half of the country. Sweden's urban areas together cover 1.5% of its land area. Sweden has a diverse Climate of Sweden, climate owing to the length of the country, which ranges from 55th parallel north, 55°N to 69th parallel north, 69°N. Sweden has been inhabited since Prehistoric Sweden, prehistoric times around 12,000 BC. The inhabitants emerged as the Geats () and Swedes (tribe), Swedes (), who formed part of the sea-faring peopl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Öland
Öland (, ; ; sometimes written ''Oland'' internationally) is the second-largest Swedish island and the smallest of the traditional provinces of Sweden. Öland has an area of and is located in the Baltic Sea just off the coast of Småland. The island has over 26,000 inhabitants. It is separated from the mainland by the Kalmar Strait and connected to it by the Öland Bridge, which opened on 30 September 1972. The county seat Kalmar is on the mainland at the other end of the bridge and is an important commercial centre related to the Öland economy. The island's two municipalities are Borgholm and Mörbylånga named after their municipal seats. Much of the island is farmland, with fertile plains aided by the mild and sunny weather during summer. Öland does not have separate political representation at the national level, and is fully integrated into Sweden as part of Kalmar County. Administration The traditional provinces of Sweden no longer serve administrative or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stora Alvaret
Stora Alvaret (; "the Great Alvar") is an alvar, a barren limestone terrace, in the southern half of the island of Öland, Sweden. Stora Alvaret is a dagger shaped expanse almost long and about at the widest north end. The area of this formation exceeds , making it the largest such expanse in Europe and comprising over one fourth of the land area of the island. Because of the thin soil mantle and high pH levels, a great assortment of vegetation is found including numerous rare species. Stora Alvaret is not devoid of trees, contrary to a common misconception; in fact, it holds a variety of sparse stunted trees akin to a pygmy forest. Stora Alvaret falls within UNESCO's Agricultural Landscape of Southern Öland, , which was designated World Heritage Site due to its extraordinary prehistory. Geological origins The limestone plain was created by glacial action from earlier ice age advances. The limestone formation itself was created about 500 million years ago in more southerl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alvar
An alvar is a biological environment based on a limestone plain with thin or no soil and, as a result, sparse grassland vegetation. Often flooded in the spring, and affected by drought in midsummer, alvars support a distinctive group of prairie-like plants. Most alvars occur either in northern Europe or around the Great Lakes in North America. This stressed habitat supports a community of rare plants and animals, including species more commonly found on prairie grasslands. Lichen and mosses are common species. Trees and bushes are absent or severely stunted. The primary cause of alvars is the shallow exposed bedrock. Flooding and drought, as noted, add to the stress of the site and prevent many species from growing. Disturbance may also play a role. In Europe, grazing is frequent, while in North America, there is some evidence that fire may also prevent encroachment by forest. The habitat also has strong competition gradients, with better competitors occupying the deeper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope movement. Processes that lead to subsidence include dissolution of underlying carbonate rock by groundwater; gradual compaction of sediments; withdrawal of fluid lava from beneath a solidified crust of rock; mining; pumping of subsurface fluids, such as groundwater or petroleum; or warping of the Earth's crust by tectonic forces. Subsidence resulting from tectonic deformation of the crust is known as tectonic subsidence and can create accommodation for sediments to accumulate and eventually lithify into sedimentary rock. Ground subsidence is of global concern to geologists, geotechnical engineers, surveyors, engineers, urban planners, landowners, and the public in general.National Research Council, 1991. ''Mitigating losses from land ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retreat Mining
Retreat mining is the removal of pillars in the underground mining Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ... technique known as room and pillar mining. In the first phase of room and pillar mining, tunnels are advanced into the coal or ore body in a rectangular pattern resembling city streets. Pillars are left between tunnels to support the weight of the overburden. The first phase is known as "mining on the advance," from the entrance toward the further reaches of the reserve. In the second phase, once advance mining has been completed, pillars are removed "on the retreat." Removing or "pulling" pillars begins far from the entrance and proceeds toward the entrance. As the pillars are removed, the mine collapses because nothing remains to support the roof and overb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shale
Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.Blatt, Harvey and Robert J. Tracy (1996) ''Petrology: Igneous, Sedimentary and Metamorphic'', 2nd ed., Freeman, pp. 281–292 Shale is characterized by its tendency to split into thin layers (Lamination (geology), laminae) less than one centimeter in thickness. This property is called ''Fissility (geology), fissility''. Shale is the most common sedimentary rock. The term ''shale'' is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the narrower sense of clay-rich fissile mudrock. Texture Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
