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Sand Box (civil Engineering)
A sand box or sand jack is a device used for removing the centering of an arch. Each prop A prop, formally known as (theatrical) property, is an object used on stage or screen by actors during a performance or screen production. In practical terms, a prop is considered to be anything movable or portable on a stage or a set, distinc ... is mounted on a sand box. After the plug is removed, the sand pours from the box, causing the centering to move downwards, diminishing the pressure from the arch, and enabling to ultimately remove it.Ashok Kumar Jain, B.C. Punmia, ''Building Construction'', Firewall Media, 2005, p. 435. References {{Reflist Arches and vaults Sand Tools ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centring
Centring, centre, centering"Centering 2, Centring 2" def. 1. Whitney, William Dwight, and Benjamin E. Smith. ''The Century dictionary and cyclopedia''. vol. 2. New York: Century Co., 1901. p. 885., or center is a type of formwork: the temporary structure upon which the stones of an arch or vault are laid during construction. Until the keystone is inserted an arch has no strength and needs the centring to keep the voussoirs in their correct relative positions. A simple centring without a truss is called a common centring. A cross piece connecting centring frames is called a lag or bolst.Ching, Frank (1995). ''A visual dictionary of architecture''. New York: Van Nostrand Reinhold. p. 3. . Centring is normally made of wood timbers, a relatively straightforward structure in a simple arch or vault; but with more complex shapes involving double curvature, such as a dome or the bottle-shaped flue in a Norman-period kitchen, clay or sand bound by a weak lime mortar would be used. Shaping ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pit Prop
A pit prop or mine prop (British and American usage, respectively) is a length of lumber used to prop up the roofs of tunnels in coal mines. Canada traditionally supplied pit props to the British market. As coal mining declined in importance and metal supports were used, the term became infrequently used. Though it was merely a log cut to a particular length, it was classified as a finished product and so got around the extra Canadian tariffs on the export of raw lumber. Because of the large quantities exported, it is probable many ended up in British pulp mills. Most pit props were made from the wood of spruce A spruce is a tree of the genus ''Picea'' (), a genus of about 35 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Earth. ''Picea'' is the sole genus in the subfami ... trees. References Coal mining {{mining-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arches And Vaults
An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it. Arches may be synonymous with vaults, but a vault may be distinguished as a continuous arch forming a roof. Arches appeared as early as the 2nd millennium BC in Mesopotamian brick architecture, and their systematic use started with the ancient Romans, who were the first to apply the technique to a wide range of structures. Basic concepts An arch is a pure compression form. It can span a large area by resolving forces into compressive stresses, and thereby eliminating tensile stresses. This is sometimes denominated "arch action". As the forces in the arch are transferred to its base, the arch pushes outward at its base, denominated "thrust". As the rise, i. e. height, of the arch decreases the outward thrust increases. In order to preserve arch action and prevent collapse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sand
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass. The composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. Calcium carbonate is the second most common type of sand, for example, aragonite, which has mostly been created, over the past 500million years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Somewhat more rarely, sand may be composed of calciu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
