PhD project description The use of TBM in future Norwegian infrastructure projects

Transcription

1 NTNU - The Norwegian University of Science and Technology PhD project description The use of TBM in future Norwegian infrastructure projects PhD candidate: Øyvind Dammyr Main supervisor: Professor Bjørn Nilsen (NTNU) Co- supervisor: Professor Kurosch Thuro (TUM) Photos from the Hallandsås TBM tunnel project in southwestern Sweden Signature PhD candidate Signature main supervisor Contents of this document: 1 Background Objectives Scope Research Method Expected results Work plan References... 9

2 1 Background Tunnel Boring Machines (TBMs) were extensively used in Norway from the 1970s to the 1990s. The technique was mostly utilized on hydropower projects for the excavation of long transfer and pressure tunnels. At the time of introduction few tunnels through hard rocks, which are predominant in Norway, had been excavated with TBMs. During the 20 years of tunnel boring, manufacturers, clients, contractors, consultants and research institutions took part in the development of TBMs for boring through harder and tougher rocks. At the start of the 1990s Norway was considered to be in the forefront regarding this type of TBM technology. NFF (1998) reports on the Norwegian TBM history. Especially for long tunnels with few access points the TBM technique often proved to be both faster and more cost effective than the traditional D&B (drill and blast) excavation method. For hydropower tunnels the smooth circular contour also contributed to a lower head loss in the waterway and the tunnel diameter could be reduced compared to a traditional D&B tunnel. Other TBM projects included sewer tunnels, tunnels for the transport of drinking water and three road tunnels. The three road tunnel projects were not optimal for the TBM technique due to their relatively short lengths. However, a great deal of experience was gained from boring of larger cross sections. Many of the positive benefits of these TBM drives where unfortunately overlooked due to not optimal planning and due to the less suitable circular profile compared to the traditional horseshoe shaped road tunnel. After the large hydropower development in Norway came to an end at the beginning of the 1990s so did the use of Tunnel Boring Machines. Today, twenty years later, few persons in the Norwegian tunneling industry have experience with TBM technology, and whilst most of the world s countries are using both techniques (TBM and D&B), with increasing use of TBMs (Lemmerer 2011), Norway is often uncritically (authors opinion) only considering the D&B technique. It is no doubt that the Norwegian D&B method is highly efficient and that it has evolved largely the last twenty years. The use of this flexible technique also results in tunnels of very good quality. However, the absence of TBM knowledge in many cases leads to the fact that TBM is not even considered or not properly examined as a possible excavation option. Especially today, where evaluations of high- speed railways are being undertaken (JBV 2012a) and where long rail (JBV 2012b) and road (SVV 2012a) tunnels are being planned in several parts of Norway, evaluations for possible TBM drives and their benefits are highly relevant. In recent years, especially after the rock collapse in the Hanekleiv road tunnel in 2006 (Nilsen et al. 2007), a debate to whether high traffic tunnels in Norway should be constructed differently has picked up. One important question is whether Norwegian high traffic tunnels should be built equal to what is regarded as standard in many European countries, with a full concrete lining as the final water and rock support (e.g. ÖVBB 2006 and ÖVBB 2011). In Europe a final lining with rock contact (no gap between lining and rock) is generally regarded as necessary to ensure the long- term stability, low maintenance costs, long service life, and required fire protection of tunnels. In Norway the standard, as 2

3 described in for example Handbook 021 (SVV 2010) by the Norwegian Public Roads Administration (NPRA), is to implement the final rock support and the water/frost support as separate layers, where the water support generally consists of a vault made of light weight concrete or relatively thin free standing constructions of polyethylene plates covered with shotcrete as fire protection (fig. 1). These systems have their weaknesses in that they are not as durable as a concrete lining and that there exist a gap between the rock and water support, which has to be inspected regularly. Ultimately, a decision to go for a standard waterproof final lining would lead to a higher construction cost for Norwegian high traffic tunnels, but it is also likely to give the public a more reliable service due to reduced maintenance needs, and to lower the total project lifetime costs. Both the Norwegian National Railway Administration (NNRA) and the NPRA have shown increased interest in these aspects the recent years, and the NPRA has started its own research program into the matter (SVV 2012b). Each method of tunneling, conventional and mechanical (boring) has its particular advantages and also disadvantages. The task of the designer and the tunnel engineer is to evaluate and compare these and then select and implement one method (Lemmerer 2011). Better knowledge about the advantages and limitations for both the D&B and especially the TBM method is in the eyes of the author in this respect necessary. Fig. 1: Illustration of the Norwegian rock and water support philosophy (by Arild W Solerød, NPRA). The primary scientific objectives of this PhD project will be on three research topics, which are listed below. These topics are believed to be of crucial importance for the successful implementation of the TBM technique in future 3

4 Norwegian infrastructure projects. The overall aim of the PhD project is to highlight possible future challenges and benefits of tunnel boring with focus on identifying good technical solutions and by addressing possible challenges with tunnel boring under typical Norwegian engineering geological conditions. 1: TBM stability and water support solutions for optimal project lifetime cost and service life. 2: Tunnel boring through weakness zones and required rock support measures. 3: Tunnel boring in high in situ rock stress environments with the occurrence of brittle failure. The importance of research point 1 has somewhat been covered in the above text, and the main focus will be on typical solutions for TBM excavations. The state of the art and most common in infrastructure TBM tunnels is to line as the TBM advances with a segmental lining, a concrete ring made out of segments that fits together and form a complete ring just behind the TBM (see e.g. Maidl et al. 2008). However, at projects with special engineering geological conditions there might be necessary to install the lining at a later stage, and hence the lining is normally constructed as a cast concrete lining behind the TBM. In this PhD project it will be important to analyze the durability of different kinds of stability and water support solutions, and to see how the traditional Norwegian solutions compare to the European standards. New tunnels shall be compared to older ones with the same or similar type of construction to identify problems. If a tunnel, which is constructed for 100 years of service life, should start to leak after a short operating time this may have huge effects for the users and the maintenance costs. New innovations are also welcomed, such as the construction of segments reinforced with steel or plastic fibers alone or in combination with the traditional rebar reinforcement (see Hansel & Guirguis 2011 and Fuente et al. 2012). This can have several advantages such as reduction in costs compared to traditional reinforcement and to better disperse forces acting in the segments, preventing/reducing concrete cracking and spalling typical resulting from the installation of the segments or from the TBM thrusting of the segments. Research point 2 involves analysis into the use of TBMs in geology of changing quality. The TBM technique is less flexible than a D&B excavation and after construction has begun it is harder to react and adapt to changing and unforeseen ground conditions. Major weakness zones or faults containing heavily crushed and altered rock mixed with gouge material represent the most difficult conditions in Norwegian hard rock tunnels (Mao et al. 2011). It is of paramount importance for future TBM tunnels that analysis into the crossing of these zones is undertaken. There are many recent experiences from tunneling through changing ground conditions in Europe (e.g. Sturk et al. 2011, Ehrbar 2008) and it will be important to look into how these relate to Norwegian geological conditions and to learn from them. It will also be important to analyze field data from ongoing projects in geology relevant to future Norwegian projects. Observations on how TBMs and the rock support perform under these conditions will be in focus. 4

5 ting equipment on each side of the main body. The first 1,700 m was bored virtually without stability problems. After the break-in period the net penetra- PhD project description Øyvind Dammyr tion was approx. 1.3 m/h and the weekly progress m. The rock material had good boreability (DRI at Research point 3 involves analysis of brittle failure theory and practice. Brittle failure is a phenomenon, which can occur where the rock mass compressive strength 65-75), is overcome but the by rock the in mass situ stress had around little underground jointing. excavations As boring (fig. 2). All the aspects of the phenomenon is not fully understood and attempts to model with brittle high failure cutterloads with traditional in the rock massive strength criterions rock such resulted as the Mohr in Coulomb heavy or vibrations the empirical of generalized the relatively Hoek- Brown light criterion body has not of succeeded. this Several researchers have looked into the phenomenon of brittle failure the recent TBM, years the (e.g. rock Martin bolting et al. 1997, equipment Ortlepp 2001, required Diederichs et extensive al. 2004, Noferesti & Rao 2010). Some have suggested a methodology for the estimation of maintenance and was eventually removed. the probability for spalling and the depth of spalling (Martin & Christiansson 2009) After and a similar about approach 1,700 has m been of advance, tested in a larger increasingly infrastructure intense project (Rojat et al. 2009). Others have tried to modify current rock strength criterions to spalling give more occurred. accurate numerical Some modelling spalling results had under been such high anticipated, rock stress conditions but the (Hajiabdolmajid intensity was et al. unexpected. 2002) and some have On used some an approach sections with uncertainty analysis to estimate spalling potential (Harrison & Hudson 2010). From the rock many experiences at the contour in Norway was we know more that or spalling less and crushed, rock bursts and resulting from brittle failure is a common occurrence in Norwegian underground excavations. the progress For future of tunnelling TBM drives further was analysis slowed into this down phenomena, due to: in the light of the newest available research, is necessary. It will be an advantage to see the installation of rock support how the theory relates to Norwegian geological conditions. As in point 2 it is important gripping to observe problems how TBMs due and rock to overbreak support perform in under the walls these conditions. Gathering of field data and observations will here be undertaken and correlated hand clearing of debris and rock fragments to the newest research in the field. 2: Overbreak due to crushing and spalling (from NFF 1998). Fig. 2 Overbreak due to crushing and spalling During the first critical phase, rock bolting was performed by jack-leg drilling. 5 Later, working platforms were added making it possible to install rock bolts du- Fig. 3 Ro diameter The sp fragment pened wh bolting a had time front-end TBM bo material into the t The norm with two needed t Furthe creased, thus cou ses. Still develop above th rock sup hind the tions bec

6 2 Objectives The overall aim of the PhD project is to highlight possible future challenges and benefits of tunnel boring at future Norwegian infrastructure projects with focus on identifying good technical solutions and by addressing possible challenges with tunnel boring under typical Norwegian engineering geological conditions. Analysis into how relevant theory and state of the art experiences applies to Norwegian conditions is here important. See also chapter 1 for a more detailed explanation of points 1 through 3. Scientific objectives: 1: TBM stability and water support solutions for optimal project lifetime cost and service life. Find the optimal stability and water support solutions. 2: Tunnel boring through weakness zones and required rock support measures. Identify challenges and propose solutions. Define the necessary rock support measures. 3: Tunnel boring in high in situ rock stress environments with the occurrence of brittle failure. Identify challenges and propose solutions. Define the necessary rock support measures. 3 Scope The focus will generally be on geological conditions typical for Norway (hard rock) and engineering geological challenges that can be expected in Norway. Soil tunnels will not be included in the work. Soft/weak rock conditions will only be evaluated in relation to weakness zones. Detailed TBM tool wear and advance rate estimations are not in the scope of this PhD project. A lot of work has already been done on the topic and several research groups are currently working on new methods and optimization of existing methods. 4 Research Method Generally: Analysis will be undertaken based on extensive literature studies of theory and practice, experiences from earlier Norwegian projects, recent European projects, and collected field data and observations from site visits. The aim is to correlate practical experiences, numerical modelling and analytical calculations, with new published research in the fields, and to relate the results to typical Norwegian engineering geological situations. The points below describe the research method in more detail. Extensive literature studies of relevant theory. It is important to review the state of the art in all the research fields stated in the scientific objectives 1 through 3 in chapter 2. Analysis of earlier experiences from TBM projects in Norway. Knowledge transfer from Norwegian TBM experts and literature studies (e.g. NFF 6

7 1998). It is important to identify typical challenges and benefits made at earlier Norwegian TBM projects. Analysis of newer experiences from TBM infrastructure projects in similar geology internationally. Knowledge transfer and literature studies. Recent European experiences in similar geology/conditions and hence challenges that are expected in future Norwegian projects are crucial. The PhD project is undertaken in a close cooperation with the Technische Universität München (TUM), Germany. This cooperation enables extensive knowledge transfer and access to relevant European TBM projects. This involves both finished projects and projects under construction. This point and the point above are relevant for all the scientific objectives listed in chapter 2. Observations and gathering of field data from possible future Norwegian and built/current international TBM projects relevant for Norwegian conditions. For research point 1 it is relevant to gather data about the type of tunnel lining and type/nature of leakage problems through the tunnel lining in the operating phase. Here also data from Norwegian tunnels with the traditional Norwegian water proofing systems will be included. The data will be evaluated with respect to the type of lining used, the geological conditions and occurrence of water during construction. Data from new tunnels will be correlated to data from older tunnels to evaluate the quality and durability of the construction and what sort of problems that are commonly seen. For research points 2 and 3 deformation data and observations of brittle failure (possible measurement of the depth of failure) are to be collected systematically from a tunnel(s) under construction. Where possible should also classification of the rock mass (with the use of more than one classification system for correlation) be performed, and in situ rock samples for lab testing be taken (e.g. for testing of the UCS (Uniaxial Compressive Strength)). The collected data will be correlated to the observed challenges with the TBM drives and compared with the published literature. It will also be used in numerical modelling and analytical calculations (see below points). It will be important to relate the data to engineering geological conditions typical for Norway when interpreting the results. The data will also be compared to earlier experiences from Norwegian projects. Laboratory experiments. For numerical modelling and analytical calculations different kinds of laboratory tests might have to be undertaken (UCS with more) unless this has already been done and provided by others. Numerical modelling of deformations, stability and rock support. 2D and possibly 3D modelling will be undertaken and correlated with in situ observations. Analytical calculations of deformations and stability will be done and correlated with in situ observations. Correlations between numerical modelling and analytical results. This point is important to assure that both numerical and analytical results can be regarded as reasonable and to identify differences between numerical and analytical approaches. 7

8 5 Expected results Generally: A better understanding of how state of the art practice and theory relates to Norwegian engineering geological conditions will help to improve the decision basis for tunnel boring in Norway in the future. Below are some expected results listed together with how the outcome of the research can be applied in an industrial context or be useful to public administration. Highlight the possibilities and challenges (limitations) and hence better the decision basis for the choice of TBM in future Norwegian infrastructure projects. This is very relevant for contractors, consultants and project owners (e.g. the NPRA and the NNRA) and will benefit the society as a whole as typical projects will be both road and railway tunnels. Detailed analysis into three specific research topics will contribute to concrete recommendations on how to approach these different problems. The choice of the right support solutions to enable a longer project life and to reduce maintenance costs are very important for new projects and the direction the Norwegian tunnel philosophy will take in the future. Detailed knowledge about crossing of weakness zones and operation under high in situ stress concentrations are important to ensure the choice of the right technical solutions and to ensure the successful completion of future projects. Correlations of field data and in situ observations with numerical modelling, analytical calculations and published research may contribute to confirm or/and to optimize existing theory and practice. Hence, this will contribute to the research in the respective fields. 6 Work plan Shown below is a plan for the scheduled work. Planned papers are listed with numbers 1-5. Paper one is already sent in and accepted. It will be published at the EUROCK 2012 rock mechanics conference in Stockholm, Sweden at the end of May Paper 2 is in the works and the plan is that it will be published within the end of PhDAtimeplan Courses GB8310 GB8306 IFEL8000 GB8406 IndividualAreadingAcourse WorkAatANTNU TeachingArelatedA(25%) Research LitteratureAstudies FieldAworkA(andAlab.) Analysis PublicationAwork PaperA1 PaperA2 PaperA3 PaperA4 PaperA5A(maybe) CompletionAofAPhDAthesis PhDAdefence Spring Autumn Spring Autumn Spring Autumn Spring Autumn Spring 8

9 7 References Diederichs, M., Kaiser, P., & Eberhardt, E Damage initiation and propagation in hard rock during tunnelling and the influence of near- face stress rotation. International Journal of Rock Mechanics & Mining Sciences, 41, Ehrbar, H Gotthard base tunnel, Switzerland. Experiences with different tunneling methods. In: Proceedings of the 2nd Congresso Brasileiro de Túneis e Estruturas Subterrâneas. Seminário Internacional South American Tunnelling, São Paulo, Brazil, Fuente A., Pujadas, P., Blanco, A. & Aguado, A Experiences in Barcelona with the use of fibres in segmental linings. Tunnelling and Underground Space Technology 27 (2012) Hajiabdolmajid, V., Kaiser, P., & Martin, C Modelling brittle failure of r ock. International Journal of Rock Mechanics & Mining Sciences, 39, Hansel, D. & Guirguis, P Steel- fibre- reinforced segmental linings: State- of- the- art and completed projects. Tunnel 1/2011. Harrison, J. P. & Hudson, J. A Incorporating Parameter Variability in Rock Mechanics Analyses: Fuzzy Mathematics Applied to Underground Rock Spalling. Rock Mechanics and Rock Engineering, 43, JBV, 2012a. The Norwegian National Rail Administration (JBV) high- speed rail feasibility study. Online presentations of the evaluation. URL: n/ Accessed: JBV, 2012b. The Follobanen project. Online information. URL: S- - - Ski/Dette- er- Oslo- Ski/ Accessed: Lemmerer, J Selection of tunneling method (Editorial). Geomechanics and Tunneling 4 (4): 278. Maidl, B., Schmid, L., Ritz, W. & Herrenknecht, M Hardrock Tunnel Boring Machines. Berlin: Ernst & Sohn. Mao, D., Nilsen, B. & Lu, M Analysis of loading effects on reinforced shotcrete ribs caused by weakness zone containing swelling clay. Tunnelling and Underground Space Technology 26 (2011) Martin, C., & Christiansson, R Estimating the potential for spalling around a deep nuclear waste repository in crystalline rock. International Journal of Rock Mechanics & Mining Sciences, 46, Martin, C., Read, R., & Martino, J Observations of Brittle Failure Around a Circular Test Tunnel. International Journal of Rock Mechanics and Mining Sciences, 34 (7), NFF, Publication No. 11: Norwegian TBM tunneling. Oslo: Norwegian Tunneling Society, NFF. Available online, URL: Nilsen, B., Bollingmo, P. & Nordgulen, Ø Raset i Hanekleivtunnelen 25. desember Rapport fra undersøkelsesgruppen. URL: Accessed: Noferesti, H., & Rao, K. S New Observations on the Brittle Failure Process of Simulated Crystalline Rocks. Rock Mechanics and Rock Engineering, 43,

10 Ortlepp, W The behaviour of tunnels at great depth under large static and dynamic pressures. Tunnelling and Underground Space Technology, 16, Rojat, F., Labiouse, V., Kaiser, P., & Descoeudres, F Brittle Rock Failure in the Steg Lateral Adit of the Lötschberg Base Tunnel. Rock Mechanics and Rock Engineering, 42, Sturk, R., Dudouit, F., Aurell, 0. & Eriksson, S Summary of the first TBM drive at the Hallandsas project. Rapid Excavation and Tunneling Conference (RETC) proceedings. Society for Mining, Metallurgy, and Exploration, Inc. SVV, 2012a. The Norwegian Public Roads Administration (SVV). E39 Rogfast sub- sea road- tunnel. Available online, URL: Accessed: SVV, 2012b. Modern road tunnels research and development program. Online information. URL: Moderne+vegtunneler Accessed: SVV, Håndbok 021 Vegtunneler. Available online, URL: ÖVBB, Österreichische Vereinigung für Beton und Bautechnik Guideline "Concrete Segmental Lining Systems" ÖVBB, Österreichische Vereinigung für Beton und Bautechnik Guideline "Inner Shell Concrete" 10