道路畢業(yè)設(shè)計外文翻譯---交通系統(tǒng)-交通線路-展示頁
2025-01-31 01:37本頁面
【正文】 abilized by mixing some other material with it. This may be bitumen or a grout of concrete or some other substance. The base course, which is made of either crushed stone or a layer of thinlymixed concrete, es next, the wearing surface, which may be a layer of asphalt or a series of reinforced concrete slabs, is then laid. A concrete surface be laid in segments separated by joints to allow for expansion and contraction under difffering weather 7 conditions. One method of laying a reinforced concrete wearing surface is to put down the steel rods, usually in the form of a grill or mesh, after a certain proportion of the concrete has been poured. The top level must be poured within twenty minutes of the pouring of the bottom level to assure proper bonding. Anther method is to pour the entire thickness of concrete and then force the steel mesh down i nto it to a predetermined level. A group of machines collectively callled a concrete train usually perform these operations at a rate of about threefourths of a meter per minute. A single new machine called a slipform pawer can perform all the different jobs of a concrete train excep laying the reinforcing mesh. However, a technique has been worked out in which the mesh is held in place before the machine passes over it and pours concrete aroung it . The slipform paver can operate at a rate of about two meters per minute. The construction of airport runways follows similar procedures, except that the slabs in a runway are much wider then those in a highway. Airport runways must also be designed to carry the heavy load of the big modern jumbo jets, as well as to withstanf enormous blastes of heat from the engines of heat form the engines of the impact fatcor is also greater with airplanes than with automobiles. Highways differ form airport runways, however, insize and strength rather than design and construction methods. If huge concrete freeways are the transportation phenomenon of hort this cen
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