2. 外语
  3. 轨道的作用 轨道有三种主要作用：支承列车重量，为顺利运行提供平滑表面和引导列车车轮前进。 铁路线路应尽可能地平直，因为坡度和曲线会增加机车的负荷和加速对轨道的磨损。牵引一列(装载客货的)列车爬上1％的坡度所需要的牵引力是平直的轨道上的(牵引力)

轨道的作用 轨道有三种主要作用：支承列车重量，为顺利运行提供平滑表面和引导列车车轮前进。 铁路线路应尽可能地平直，因为坡度和曲线会增加机车的负荷和加速对轨道的磨损。牵引一列(装载客货的)列车爬上1％的坡度所需要的牵引力是平直的轨道上的(牵引力)

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问题    轨道的作用
   轨道有三种主要作用：支承列车重量，为顺利运行提供平滑表面和引导列车车轮前进。
   铁路线路应尽可能地平直，因为坡度和曲线会增加机车的负荷和加速对轨道的磨损。牵引一列(装载客货的)列车爬上1％的坡度所需要的牵引力是平直的轨道上的(牵引力)的五倍，而一度弯曲线需要增加牵引力12．5％一25％。
   路基是上面铺着道碴、轨枕和钢轨的底基。路基有两种类型：路堑和路堤。路基应坚固，排水性好并具有足够的面积和厚度。
   钢轨承受着机车，车厢加在轨道上的荷载，轨枕支承着钢轨，而道碴又支承着轨枕。今天，在运输繁忙的线路上使用着每米重达60公斤或更重的钢轨，所谓T形轨(由其形状命名)一直持续使用，因为经验证明这种钢轨是最实用，最经济的。
   轨枕使钢轨之间保持适当的距离，轨枕支承着钢轨并把荷重传递到下面的道碴垫层上。经过现代化的化学方法处理后，枕木的使用寿命几乎增加了两倍，即由平均使用不到10年延长到20多年。为了节省木材和其他原因，混凝土轨枕发展得非常迅速，以至现在可以认为混凝土是制造轨枕的理想材料。
   为了减少由钢轨传递的载荷冲击力可造成的(对轨枕的)机械磨损，在轨枕与钢轨之间插人金属垫板，这些垫板把钢轨所承受的负担传递到宽阔的轨枕面积上，从而有助于保护轨枕不受轨底切割和磨损作用的影响。车轮摩擦造成钢轨纵向爬行的趋势，特别是在多轨线路上，因此使用防爬器来防止这种移动。把防爬器安装到钢轨上，紧靠着轨枕的边缘。
   道碴，一般是由碎石、煤渣、砾石或矿渣组成。道碴支承并衬垫着轨枕，使轨枕保持在适当的位置上，并帮助把轨道承受的载荷分散到路基上。道碴还有利于排水，从而就增加了轨道的稳固性和平稳的运行质量。
   当列车进入弯道时，它的自然趋势是一直前进。列车之所以转弯是因为曲线外轨道迫使它这样做。为了使列车安全地、更平衡地通过弯道，外轨要超高，也就是升高到高于内轨的高度，这样做是为了平衡列车由于弯道的缘故离开直线运动而产生的离心力。一定曲线弯道的正确超高度要取决于列车运行的速度。
选项
答案 Functions of the Track Track has three main functions. It must support the load, provide a smooth surface for easy movement and guide the wheels of the train. The railroad line should be as level and straight as can be achieved because grades and curves increase the burden on the locomotive and the wear on the track. The tractive effort required to pull a load up a 1% grade is about five times what is required on straight level track and a curvature of 1 degree requires an increase of from 12. 5% to 25% in tractive effort. Road-bed is the subgrade on which are laid the ballast, ties and rails. There are two types of it: cut and fill. It should be firm, well drained and of adequate dimensions. Steel rails support the load which locomotives and cars impose on the track. Ties support the rails and ballast supports the ties. Today, rail weighing as many as 60 kilogrammes or more to the metre is in use on lines handling heavy traffic. The use of the so-called T-rail (from its shape) has persisted because experience has shown it is the most practical and economical form of rail. The ties keep the rails the proper distance apart, support them and transmit the load to the ballast cushion beneath. With modern methods of chemical treatment, the service life of ties has been approximately trebled, from less than 10 years to more than 20 years, on the average. For the saving of timber and other reasons, concrete ties have developed so rapidly that concrete is now considered to be the ideal material for railway ties. To reduce mechanical wear from impact of loads transmitted through the rail, metal tie plates are inserted between the rail and the tie. These plates spread the rail burden over a wide tie area, and thus help to protect the tie from the cutting and wearing effect of the rail base. Wheel friction causes a tendency for rails "to creep" longitudinally, especially on multiple tracks where the trains generally run in the same direction on each track. Small anchors, or anticreepers, applied to the rail and bearing against the edge of the tie are used to check this movement. Ballast, usually of crushed rock, cinder, gravel or mine waste, supports and cushions the ties and helps to keep them in proper positions as well as to distribute the track load over the road-bed. It also facilitates drainage, thereby promoting firmness and smooth riding qualities of the track. As a train enters a curve, its natural tendency is to continue going straight ahead. It turns only because the outside rail forces it to do so. To permit trains to traverse curves with safety and greater smoothness, the outer rail is super-elevated, or raised above the height of the inner rail so as to balance the forces set up when the movement of the train is diverted from a straight line by the rails of a curve. The right amount of super-elevation for a given curve depends on the train speeds.
解析
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