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1、西 南 交 通 大 学本科毕业设计外文翻译年 级: 学 号: 姓 名: 专 业: 指导老师: 2012 年 6月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 average progress rates and p
2、ractical 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 remarks on rock TBM tunnelling in relation to the selection and dimensioning of the machine, the attention is
3、posed on the limiting geological conditions which may be envisaged with respect to the use of TBM tunnelling and 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 i
4、s centered upon the relatively 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 project experience, the point of view is illustrated by
5、 case examples, which give the opportunity to underline specific difficulties encountered and recommendations.INTRODUCTION TBM excavation represent a big investment in an unflexible but potentially very fast method of excavating and supporting a rock tunnel (Barton, 1996). When unfavorable condition
6、s are encountered without warning, time schedule and practical consequences are often far greater 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 qu
7、ality (i.e. 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 performance has not an absolute value: the influence is in fact to be refe
8、rred 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 was to overcome the limits imposed by local geology, the economic challenges and schedule competitions of the drill and blast method and other so-c
9、alled traditional excavation methods. A prominent example is given by the recent (from 1995 to 2000) construction of the one tube 24.5 km long Laerdal Tunnel in Norway, the worlds longest road tunnel. The 100m*m cross section tunnel is being excavation in a Precambrian gneiss, a very good and stable
10、 rock mass: the supports are on average only 7-8 rock bolts plus a 7cm thick shotcrete lining per meter of tunnel. The excavation is carried out by the drill and blast method, which been evaluated to be less expensive and more reliable than the ;use of alarge diameter TBM. The average progress rate
11、is 4.8 5.0 km per year with two faces, against the 2.3-4.8 km per year, estimated for a large diameter TBM (Kovari et al., 1993) With this background in mind, this paper is intended to address the problem of TBM tunnelling in difficult ground conditions. Based on a few selected case examples, the di
12、scussion is centered upon the relatively more important or difficult ground conditions which can be listed as follows: borability limits; instability of excavation walls; instability of excavation face; faut zones; squeezing. ROCK TBM TUNNELLING The practically infinity number of combinations rock,
13、soil and environmental conditions which may be encountered during tunnel excavation has determined a great difference in the types and characteristics of the available TBMs . There are many different schemes for the classification of tunnelling machines. For the example the AITES/ITA Working Group N
14、o.14 (Mechnisation of Excavation ) is currently working on the definition of an internationally acceptable classification of TBMs with the purpose of establishing terminology and “terminology” for the optimum choice of the machine (Table 1). Rock tunnelling machine can be grouped in to three main ca
15、tegories (Table2): Unshielded TBM (i.e. Open TBM), Single Shielded TBM which is the way of creating new types of TBMs that are suitable for application over a wider range of geological conditions, even though the distinction between TBM for rock and TBM for soft ground remains. From the point of vie
16、w of rock TBM dimensioning, it is necessary to point out that, although TBMs 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 therefore that of the TBM.As easily perceived, the reasons for limiting the tunnel di
17、ameter are: n the potential of a TBM in hard rock decreases with in increasing diameter (Kovari et al., 1993; Bruland. 1998); n There are technological limits for the maximum dimensions of some major TBM components, for example, the bearing and the head; n The intensities of both the instability phe
18、nomena and the induced convergence also increase with increasing 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 TBMs in rocks of different qualities and strengths for excavation diameters up to 1
19、2-12.5 m. Beyond 13.5-14 m excavation diameter, the present technology is probably not up to the level of guaranteeing a good performance of TBMs in hard rook. Designers should take into account these limits during the tunnel design phase, making use whenever possible of the advantages offered by th
20、e 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 t
21、hree lanes. In the case of railway tunnels, 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 TBMs could possibly be achieved through the standardization of the section types for road, motorway, and railway tunnels.
22、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 TBM, in terms of direct project costs, is rekatively insignificant. Failure to achieve the desired results and maintain the t
23、ime 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 machin
24、es 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 abo
25、ve 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 TBMs have a wider range of application than the open TBMs; - this difference in the range of application increases with in creasing diamet
26、er of excavation; - open TBMs 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 t
27、he 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 the tunnel to be constr
28、ucted. - It should be recalled that in a tunnelling project there are other problems which need to be solved in addition to the technical ones, i.e.: - one should be reminded that today there are TBMs which can reduce significantly the number of geological situations which cause important problems t
29、o face advance assuming that these that these TBMs are correctly designed and utilized; - there still exist some limiting situations which can only be overcome by special interventions with unavoidable consequences on the construction time and cost of the project;- the use of mixed shields is not a
30、solution for overcoming the limits of TBM application in rock, except for some very special cases; in the design of TBMs for rock and in the definition of special interventions for application to a given situation; - the importance of the contractors expertise and, above all, the personnel director
31、and technical staff on set, is often not given the right attention, while in reality it plays a primary role in the functioning of a TBM, particularly under limiting condition; - the time and cost for overcoming limiting conditions, in a tunnelling project acquired through a competitive bidding, sho
32、uld be supported by the client. He is to account for adequate margins in programming and budgeting whenever a tunnel is to be excavated in difficult ground conditions, according to a risk a assessement evaluation; this point is valid also for tunnelling projects to be construct by the drill and blas
33、t method.Given that a TBM capable of advancing under whatever geological condition does not the type of the TBM used, and the design and special construction characteristics the TBM adopted.In fact, it is not sufficient to just order from a qualified manufacturer a particular type of TBM; instead, a
34、 continuous collaboration and control of all design and construction details are essential by its intended user, the contractor. The is particularly true as far as there are still no “Accepted Standards” for the design and construction of a type TBM, and each TBM to be constructed is to be considere
35、d as a prototype, one different from another one , given that:- the design and manufacturing of TBMs is a continuous, technologically innovative process, TBM - each tunnelling project has its own characteristics and each specialistic contractor has own traditions and opinions. 在不良地质条件下的隧道掘进摘要本篇论文所探讨
36、的内容是：在遇到严重减小掘进速度的不良地质条件下的隧道开挖，并提出采用，钻爆法和其他所谓的传统开挖方法进行隧道掘进时所能遇到的问题。下面是由进行掘进的有关机器选型和尺寸的说明，关注于使用进行掘进的地质条件的限制及地质和地质观测的重要性，所以，要恰当理解隧道沿线的围岩状况。讨论集中于相对重要或不良地质状况的围岩，其中包括可挖性限制，开挖洞壁的不稳定性，开挖掌子面的不稳定性，断层和挤压岩况。利用其他作者之言并基于工程经验，通过实例阐述观点，借此机会强调面临的特殊困难并给出建议。引言TBM开挖不仅意味着巨额投资，而且可以进行快速开挖和支护 (Barton, 1996)在无预警的情况下遇到不良地质条件
37、，从时间和实际产生的结果来讲采用TBM 方法进行隧道掘进远远比采用钻爆法快得多。在不良地质条件下往往产生大量的弱质岩石，这样会使隧道处于不稳定状态，或者产生大量的硬岩，会降低掘进速度。然而，据观测，采取全断面机械开挖方法，岩石状况不会影响机械运行的绝对值：实际的影响因素参考TBM类型和隧道直径。仅从该方法使用之初，全断面机械开挖方法就要克服了地质条件的限制，钻爆法和其他传统的开挖方法在经济方面的挑战和施工时间上的竞争。典型的例子就是最近（）在挪威施工的长为24.5 kmLaerdal隧道，该隧道为目前为止世界上最长的公路隧道。开挖横断面100m*m，地质年代为前寒武纪，片麻岩，岩石稳定：每米隧
38、道平均打个锚杆进行支护，外加7cm厚的喷混衬砌。使用钻爆法比使用大直径的方法进行开挖花费少，而且更可靠。从两面同时进行每年的平均速度是 4.8 5.0 km而大直径的估计每年速度为 2.3-4.8 km (Kovari et al., 1993)。了解此情况后，该论文试图解释在不良地质条件下使用TBM进行隧道掘进所遇到的问题。基于所选的几例情况，该讨论聚焦于相对重要和困难的地质情况：可挖性的限制，开挖洞壁的不稳定性，开挖掌子面的不稳定性，断层，挤压状态。硬岩隧道掘进在隧道进行开挖过程中，所面对的岩石，土壤和环境条件等一系列实际问题决定了所使用的类型和特征的不同。隧道掘进机有很多不同类别。如AI
39、TES/ITA No.14 （开挖机械）目前被认定为国际上可接受的TBM类别，该名称用于确定术语，该术语是适合选择的机器的意思（表1）。硬岩掘进机主要分为三类（表）：无护盾TBM（例如：敞开式TBM），单护盾式TBM，该种为创新型的TBM，即便存在硬岩式和软岩式TBM，该钟却适用于多种类型地质条件。就TBM的尺寸来说，有必要指出一点，虽然已经采用TBM开挖过10米以上洞径的隧道，但限定洞径及TBM的直径仍是明智之举。显而易见，洞径受限的原因如下：n 随着洞径增大，TBM在硬岩掘进方面的潜力减弱；n 大尺寸的TBM主要部件受技术条件的限制，例如，轴承和刀盘；n 随着开挖直径的扩大，不稳定现象的强
40、烈程度也会随之增强。在开挖直径达到12-12.5 m的情况下，在不同质量和强度的岩石条件下，还是有纯熟经验运用TBM进行开挖。然而对于超过13.5-14 m的开挖直径，就目前的技术而言，可能还达不到完满实现运用TBM进行硬岩开挖的水平。在隧道进行设计的阶段，设计者应该考虑到这些限制条件，利用各种有利条件，减小隧道断面，甚至还要考虑与其他隧道开挖平行进行。特别是对于高速公路隧道而言，在某些情况下，为分流交通，最好采用三条隧道，每条隧道有两条车道，而不是采用两条隧道，每条隧道有三条车道。对于铁路隧道，最好采用相对小的两条单轨隧道，而不是采用大的双轨隧道。通过公路，高速公路和铁路的标准化改造，可充分
41、发挥使用TBM的优势。使用TBM进行施工不仅机械可以再次应用于其他相同性质的施工条件，而且在施工时间和成本上也有巨大优势。众所周知，的价格，直接施工的成本相对来说都比较大。如果达不到预期的目的，没有按照原计划时间完成，就会极大地影响施工。所以，一开始尽可能使用与有关各方面最好的设备及服务很重要。总的来说，最可靠的机器就是能被分解成尽可能少的部件的简单机器(Foster, 1997). 事实上，基于经验设计的TBM在维护和生产运行过程中会频繁发生很多如下预期的事件。基于以上考虑，及最近和以前的经验，关于TBM的选型提供如下观点：更广泛地使用护盾式TBM而不是敞开式。随着开挖直径的增加，使用范围更
42、加不同带有两个支撑系统的敞开式比带有一个支撑系统的护盾式对于不稳定围岩更敏感是使用单护盾还是使用双护盾的TBM，由设计情况和的尺寸及面临的限定条件决定，而不是的类型决定单双护盾式的选择由隧道断面的设计和在隧道整个施工沿线是否进行超前衬砌决定。应该想到在隧道施工中除了技术方面，还有其他问题需要解决。人们应该知道想到,如今的可以通过合理设计和使用，规避不良地质状况所带来的重大风险。还存在一些限制的情况下，才能克服特殊干预不可避免的后果的施工时间和成本的项目；除特殊情况外，使用混合护盾式并不是克服TBM进行隧道掘进局限性的方法；应用于特定状况，设计并确定特殊需要解决的困难。承包商专业知识的重要性，首
43、先，没有给予指导和技术人员以适当的关注，事实上，正是这些人在发挥功效方面，特别是在限定条件下，发挥着首要的作用通过竞标，隧道工程中所要求的克服限定条件所花费的时间和成本应该得到客户的认可。根据评估，隧道开挖在不良围岩状况下进行，在设计和预算方面要充分地考虑到差额；此方法对采用钻爆法进行施工的隧道同样适用。假定在任何地质条件下都能步进，但这种类型的不能在实际应用中出现，采取的设计和特殊的制造性能事实上，仅仅从有资质的制造商那里订购一台特别的还远远不够；而基本的还要由使用者，承包商不断地合作并监控机器的设计制造细节。实际上，只要一种类型的还没有设计和制造的“验收标准”，制造的每一台只能视作雏形，不同于其它的，原因如下：的设计和制造在不断发展，的技术革新也在进行中。每个隧道工程都有本身的特征并且每个专家级的承包商都有自己的传统和观点。