橋梁畢業(yè)設(shè)計文獻綜述開題報告外文翻譯-橋梁設(shè)計-在線瀏覽
2025-03-24 05:47本頁面
【正文】 簽字： 年 月 日 院 （系） 意見： 簽字： 年 月 日 嘉興學(xué)院外文文獻翻譯譯文 題 目： 專業(yè)班級： 學(xué)生姓名： 學(xué)號 一、 外文原文 Traffic Tunnel Construction Whenever the proposed path of a road or railway is obstructed by a hillside, a waterway or some from of construction, the engineer designing the project has to decide 11 whether or not it is practice to construct a tunnel through or under the obstacle. In making his decision, he has not only to consider the economic aspect , but also weight up all the constructional advantages and disadvantages of the both tunneling and the alternative method of either passing around or over the obstruction. In practice, it is often found that tunneling, although costly, proves to be less expensive in the long run than any alternative system. There are instances, however, where the engineer has no choice but to pass around or over the obstacle. For example, intensely hard rock might well make tunneling extremely difficult and far too costly to even contemplate. The inability of existing road systems of many large towns to copy modern traffic requirements has made tunnel construction a proposition well worth serious consideration. Up to a point, flyover and underpasses, being the first really decisive steps to speed up and divert traffic , have eased the situation, but a considerable contribution toward a satisfactory solution can be made by underground railway work. Many of the larger cities of the world have been successfully served by underground railways for years, and most of them are still extending their works. In the meantime, 12 other cities have introduced them for the first time in an effort to reduce traffic congestion. In the broadest sense, there are two fundamentally different types of construction employed for underground systems, they are subpavement tunnels and “ tubes” , the latter being situated at a far greater depth. The technique in both forms has improved dramatically over the years. The decision of city planning authorities as to whether a subpavement or “ tube” system should be adopted, depends a great deal on what type of public transport system already exists. If a perfectly efficient surface tramway system is functioning at the time, it is often found advantageous to extend it as a subpavement system. Normally, it is relatively straightforward to provide a ramped connection between the existing street level system and the underground extension. On the other hand, it may prove more satisfactory to reanize the public transport system and provide an entirely separate tube system, working independently form the service at steel level. Modern equipment and ingenuity have enabled the construction of tunnels to be far less laborious than hitherto. In applying the method known as the “ Berlin Building System” , firstly, the open excavation is taken down to a depth of between 13 12 and 25 meters. The sides of the excavation are supported by lines of driven steel, piles, as used during the excavation for
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