公路别业设计外文文献.doc

毕业设计/论文 外 文 文 献 翻 译 院 系 城市建设学院 专 业 班 级 土木工程0803 姓　 名 胡 求 实 原 文 出 处 English for Civil Engineering 评 分 指 导 教 师 华中科技大学武昌分校 20 年 月 日 Road Engineering When we speed along a modern highway, we rarely stop to think what it is we are riding on. In order that economic activity can take place, people, goods and materials must move from place to place. The necessary movement has to some extent always been possible, but the growth in economic activity placed demands on the transport system. This system developed to meet the new needs much more rapidly than it had previously, the economy expanded further, generating more traffic, and in this interactive way were produced canals and turnpike roads, then railways and most latterly a network of modern roads. Almost all roads are built in two or more layers, or courses, of rocks or stone. The bottom layer is 10 or 20 centimeters thick and usually made up of larger stones. The upper course has smaller stones and is about 8cm thick. The surface layer of road must withstand the weight of heavy vehicles. It must also prevent water from seeping into the roadbed and destroying it. How Is a Modern Road Built The first step in building a road is to plan the route, and sometimes the route has been decided by the nature of the land. Then the details are planned :the width of the highway, the number of driving lanes, the number and location of entrances and exits, and the essential strength of the road. All these depend on the amount of traffic that is expected. Modern roads are usually planned for the next 20 yearstraffic. The next step is the testing of the earth foundation on which the road is to rest. Engineers carefully study the soil to learn how solid it is, how much moisture it contains, and how well it drains. Then they decide how the soil should be prepared and packed to provide a good, sturdy foundati