隧道外文翻譯

1、TBM TUNNELLING IN DIFFICULT GROUND CONDITIONGiovanni Barla and Sebastiano PelizzaABSTRACTThis paper is to discuss TBM tunneling in difficult ground conditions, when problems are met which may reduce dramatically the

2、 average progress rates and practical consequences may be such as to pose serious questions on the use of mechanized TBM tunnelling versus drill blast and other so-called traditional excavation methods. Following a few r

3、emarks on rock TBM tunnelling in relation to the selection and dimensioning of the machine, the attention is posed on the limiting geological conditions which may be envisaged with respect to the use of TBM tunnelling an

4、d on the importance of geological and geotechnical investigations, in order to derive an appropriate understanding of the rock mass conditions along the line of the tunnel. The discussion is centered upon the relatively

5、more important or difficult ground conditions including borability limits, instability of excavation walls, instability of excavation face, fault zones and squeezing. Whenever available to the authors and based on projec

6、t experience, the point of view is illustrated by case examples, which give the opportunity to underline specific difficulties encountered and recommendations.INTRODUCTIONTBM excavation represent a big investment in an u

7、nflexible but potentially very fast method of excavating and supporting a rock tunnel (Barton, 1996). When unfavorable conditions are encountered without warning, time schedule and practical consequences are often far gr

8、eater in a TBM driven tunnel than in a drill and blast tunnel. The unfavorable conditions can be produced by either a rock mass of very poor quality causing instability of the tunnel or a rock mass of very quality (i.e.

9、strong and massive rock mass) determining very low penetration rates. However, it is to be observed that when using the full face mechanized excavation method, the influence of the rock mass quality on the machine perfor

10、mance has not an absolute value: the influence is in fact to be referred to both the TBM type used and the tunnel diameter.Right from the beginning of its earliest applications, the use of full face mechanized excavation

11、 was to overcome the limits imposed by local geology, the that, although TBM’s of more than 10 m in excavation diameter have been constructed, it is always advisable to try to limit the maximum size of the tunnel and the

12、refore that of the TBM.As easily perceived, the reasons for limiting the tunnel diameter are: ? the potential of a TBM in hard rock decreases with in increasing diameter (Kovari et al., 1993; Bruland. 1998); ? There are

13、technological limits for the maximum dimensions of some major TBM components, for example, the bearing and the head;? The intensities of both the instability phenomena and the induced convergence also increase with incre

14、asing diameter of the excavation (Tseng et al., 1998; Barla G. and Barla M., 1998). There already exists a positive and consolidated experience in the use of TBM’s in rocks of different qualities and strengths for excava

15、tion diameters up to 12-12.5 m.. Beyond 13.5-14 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 t

16、hese 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.

17、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 t

18、unnels, it is better to have two relatively small, single-track tunnels, rather than a large, double-track tunnel. A great help in the use of TBM’s could possibly be achieved through the standardization of the section ty

19、pes for road, motorway, and railway tunnels. The could favour the re-use of homogeneous construction works, in addition to gaining considerable advantages in construction times and costs. As well known, the value of the

20、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 impor