土木工程外文翻译---在不良地质条件下的隧道掘进-建筑结构(编辑修改稿)

土木工程外文翻译---在不良地质条件下的隧道掘进-建筑结构(编辑修改稿)内容摘要：

rocks of different qualities and strengths for excavation diameters up to m.. Beyond m excavation diameter, the present technology is probably not up to the level of guaranteeing a good performance of TBM’s in hard rook. Designers should take into account these limits during the tunnel design phase, making use whenever possible of the advantages offered by the reduced sections of the tunnel or even by considering the possibility of having other tunnel running in parallel. This is particularly true for motorway tunnel where, in some cases, it is preferable to make tripe tunnels each with two lanes for the traffic flow rathen than twin tunnels each with three lanes. In the case of railway tunnels, it is better to have two relatively small, singletrack tunnels, rather than a large, doubletrack tunnel. 西南交通大学本科 毕业设计 第 4 页 A great help in the use of TBM’s could possibly be achieved through the standardization of the section types for road, motorway, and railway tunnels. The could favour the reuse of homogeneous construction works, in addition to gaining considerable advantages in construction times and costs. As well known, the value of the TBM, in terms of direct project costs, is rekatively insignificant. Failure to achieve the desired results and maintain the time schedule, however, significantly affects the project. From the outset it is therefore important to adopt the approach of utilizing the best possible equipment, as far as all the aspects pertaining to the TBM, and the supporting services are concerned. Generally speaking, the most reliable machines are the simple ones as they have the least amount of equipment that can break down (Foster, 1997). In fact, the TBM that is designed to cover all eventualities has too frequently in the past, tended to be problematic in service and produced performances below expectations. On the basis of the above considerations and recent and past experience, it is possible to establish the following points regarding the selection of the type of TBM: TBM the shielded TBM’s have a wider range of application than the open TBM’s。 this difference in the range of application increases with in creasing diameter of excavation。 open TBM’s with a double system of grippers are more sensitive to unstable ground than shield s with only system of grippers。 the wider or narrower range of application of a single shielded TBM, with respect to the double shielded one, depends on the design and dimensioning of the TBM and on the type of limiting situations to be faced, rather than the TBM type。 the choice between a single shielded and a double shielded TBM depends on the design of the tunnel section and whether it is necessary to install a precast lining along the entire length of t。