1 Statistics on Tunnels under Construction 2007/08
As in previous years, the STUVA also undertook a survey of current tunnelling projects in Germany at the turn-of-the-year 2007/08. The outcome is compiled in tabular form for the month December 2007 and subsequently assessed. The table follows up its predecessors published for the years 1978  till 2007 . Only such tunnels and sewer structures, which possess an accessible excavated cross-section, i.e. a clear minimum diameter of 1,000 mm or including the pipe wall, a minimum cross-section of roughly 1 m³, are listed. On the other hand, trenchless small headings, which in recent years, have frequently been executed in conjunction with collector construction, the relevant domestic connections or also for pipe-jacking beneath rail and road facilities, are not considered.
The tunnel projects under construction at the turn-of-the-year 2007/08 are not listed in detail; however, data can be obtained from STUVA’s Internet pages (http://www.stuva.de). In these tables, the numbering of the tunnel projects indicates the relationship with the data material stemming from previous years. In detail, it constitutes single or double identification letters, a two-digit continuous registration as well as a two-digit annual identification number. The identification letters serve to provide a brief assessment of the planned tunnel use:
US Underground, urban and rapid transit rail tunnels
B Main-line tunnels
S Urban and trunk road tunnels
V Water and other supply tunnels
A Sewage tunnels
So Miscellaneous tunnels
GS Basic redevelopment of tunnels
Accordingly the identification number US 0105 indicates that it refers to a tunnel project with the ongoing number 1 from the field of Underground, urban and rapid transit tunnels, which was included for the first time in the statistics in 2005. The above-mentioned method of identification was selected against the background that the majority of construction sites, especially those from the transportation tunnel sector, run for two or three years or even more. This kind of registration has proved itself in order to avoid projects being counted twice and to identify the new construction volume that had to be included. Relevant pointers relating to the calculation of the construction lengths as well as the excavated volumes are contained in Table 1. Apart from the details for the turn-of-the-year 2007/08, the figures from the two previous years are to be found there for comparison.
By and large, the tunnel lists on the STUVA home page provide information on the location and subsequent use of the tunnels that are included, their length and cross-sections as well as the ground conditions mainly encountered. The applied construction method is explained in brief and the scheduled construction time given. As far as possible, the clients, designers and contractors are named, in alphabetical order. Furthermore, constructional or technical aspects of a special nature are provided for many projects.
When comparing transportation tunnels with supply and disposal tunnels, information on the excavated volumes of the individual measures makes it possible to estimate the actual extent of the pertinent measures in a better manner than simply details of the lengths on their own. However, the following should be observed when comparing the excavated volume: whereas the excavated volumes for trenchless construction measures can be determined without any doubt, the comparative value for cut-and-cover methods can first be obtained through reducing the entire soil that was extracted by the amount required for refilling.
Table 1 provides a picture of the overall tunnelling length under construction at the end of the year in question and the related construction volume. For the turn-of-the-year 2007/ 2008, Fig. 1 also contains the driven length and the excavation volume in accordance with the type of tunnel use shown in graphic form.
A general comparison of the figures in Table 1 reveals that the driven length of transportation tunnels again increased at the turn-of-the-year 2007/08 with altogether some 111 km compared with just under 90 km the previous year. Build-ing activities on the Under-ground, urban and rapid transit sector significantly increased and there was also a clear increase registered in conjunction with main-line railway building compared with the previous year. As far as road building was concerned this continued to drop.
If one considers the data relating to excavated volume, there is a length-related ratio of approx. 30:1 as against a volume-related one of almost 271:1 when comparing transportation tunnels on the one hand with supply and disposal facilities on the other (please also see Fig. 1).
The question pertaining to the completeness of the data obtained from the survey carried out among construction companies and consultants is difficult to assess. In order to arrive at greater reliability in this respect, the cities engaged in Underground, urban and rapid transit construction activities, the Deutsche Bahn AG were requested to supply data within the scope of the 2007/08 survey as was the case in previous years. The Federal Ministry of Transport, Building and Urban Affairs provided data for the federal trunk road tunnels . In a large number of cases, the replies from these authorities as well as from the Deutsche Bahn AG resulted in important additions and corrections. At this point, a special word of thanks to the Federal Ministry of Transport, Building and Urban Affairs, the Deutsche Bahn AG, the other authorities and clients mentioned and the architects and construction firms involved for their assistance in compiling the statistics for current tunnelling projects.
In the following, the results of the survey as of December 2007 are evaluated more thoroughly in various ways in order to obtain an up-to-date overview of tunnelling in Germany. In order to substantiate this, the comprehensive explanations relating to the structures to be found in “Underground Con-struction in Germany 2005”, containing a large number of examples presented in both illustrated and written form are referred to :
M This time around the main activities relating to inner-urban rail tunnelling (Table section US) took place in Hamburg, where a total of almost 6.7 km of Underground tunnels was being built at the turn-of-the-year 2007/08. Currently around 6.3 km of Underground tunnels is being produced. Hamburg accounts for 4.2 km. Further tunnel projects are being built in Berlin (3.6 km), Düsseldorf (3.2 km), Munich (3.2 km) and Nuremberg (1.4 km). M The length-related share of trenchless construction methods with regard to inner-urban rail tunnel construction amounted to some 17.2 km at the end of 2007 – accounting for around almost 70 % (approx. 83 % the previous year) of the national construction volume overall for Underground, urban and rapid transit systems. Of this total, some 4 % was accounted for by shotcreting methods (0 % the previous year) and roughly 66 % (83 % the previous year) by shield driving. Fig. 2a provides a survey of the proportions accounted for by the various tunnelling methods. In this connection, the upper diagram in Fig. 3a shows the length-related proportion of trenchless construction methods in Under-ground, urban and rapid transit railway construction during the last 20 years. In this diagram, the division of trenchless construction methods according to shotcreting applications and shield drives is specially marked.
M The main-line railway tunnels contained in Part B largely relate to measures in conjunction with the new or upgrading construction programme for the high-speed lines of the Deutsche Bahn AG. Among the few current tunnelling measures taking place (Fig. 1) the major projects Bleßberg (8.3 km) and the Silberberg Tunnel (7.4 km), which has been newly embarked on – as part of the new and upgraded Nuremberg – Erfurt line – are especially worthy of mention. These tunnels – like the majority of the tunnels for the dB high-speed routes – are mainly built by trenchless means (Fig. 3b). The Finne Tunnel (6.9 km) part of the new Erfurt–Halle/Leipzig route, whose 2 tubes were excavated by shield drivage, forms an exception.
M Road tunnel construction (Part S of table) just like the 2 other transportation sectors, has constantly been subjected to pronounced fluctuations in recent years. This becomes clearly evident from the award curve in Fig. 4 and above all, from the curve pertaining to the award and length-related proportions in Fig. 5. Road tunnels are generally driven by mining means unless inner-urban tunnels are concerned (Photo 2). In this connection, shotcreting together with drill + blast predominate in the majority of cases (Fig. 3c).
In the parts of the table V and A relating to supply and disposal tunnels, only those with major diameters – as initially explained – are listed. The smallest cross-sections are roughly 1.0 m in diameter, the largest about 3–4 m. All of the supply and disposal tunnels assessed at the turn-of-the-year are driven by trenchless means. In the case of waste disposal tunnels, pipe-jacking continues to prevail as it has done in previous years. Furthermore, in compiling sewer statistics, it should be pointed out that only main collectors are dealt with here. The considerably greater part accounted for by collectors with smaller cross-sections mostly driven close to the surface by means of cut-and-cover, is not listed here, as generally speaking, this is not classified as tunnelling.
As far as tunnels under construction at the end of 2007 are concerned, their distribution according to federal states is also of interest. Table 3 and Fig. 6 provide more details in this respect.
If one compares the newly obtained driven lengths and excavated volumes for the turn-of-the-year for transportation tunnels based on the statistics of recent years, then a revealing picture of just how contracts are awarded is obtained. In this connection, Fig. 4 clearly shows the important influence of the DB’s new lines and displays the fickleness on the part of public authorities in awarding new tunnelling contracts, something which constantly gives rise to complaints by the construction industry. After a steep rise in awards during the years 1996 till 1999 (resulting from activities in conjunction with the new Cologne–Rhine/Main route) an equally steep down-turn was registered over the next 2 to 3 years (please also see Fig. 5). As a consequence, as far as providing work for the available capacities in the tunnelling industry (design and execution) is concerned, expectations are still concentrated on construction measures in conjunction with further new and upgraded lines for the Deutsche Bahn AG as well as on the national trunk roads sector.
2 Planned Tunnelling Projects
The results of the survey relating to concretely planned tunnels and those to be commissioned in the near future are naturally of special interest to the construction industry and consultants. Table 2 presents the award period as from 2008.
When appraising the data in Table 2, a good proportion of the relatively high volume of Underground, urban and rapid transit rail tunnels, has been commissioned. In this connection, the cities of Munich with almost 21 km, Stuttgart with around 9 km, and Dortmund with almost 4 km along with Karlsruhe, Berlin and Duisburg with some 3 km each of the planned tunnel sections account for the remaining projects.
Regarding the particularly high proportion of main-line tunnels, it can be ascertained that this relates principally to the numerous tunnels for the projects involving the upgrading and new development of the route between Stuttgart and Augsburg – amounting to some 70 km, the Stuttgart 21 main line project involving roughly 53 km as well as the New Erfurt–Leipzig/Halle line involving almost 31 km.
The unaltered high volume of projected road tunnels continues to stand out. More than two thirds of the listed projects concern the old (western) federal states (please see Table 4). The measures that are being planned in the new (eastern) federal states are mainly at the preliminary planning stage and, consequently, not yet sufficiently advanced to be included in the statistics. The planning on this sector is primarily being carried out in conjunction with the “German Unity Projects – Road”.
The 156 km of planned road tunnels listed in Table 2 has at least reached the planning approval stage. Furthermore, further road tunnels totalling almost 100 km in length are additionally planned. They have to be added to the figures contained in Table 2. For a part of these projects, the environmental compatibility test (UVP) has already been concluded or the route alignment has been determined. However, their realisation has not been absolutely secured, neither in terms of scheduling nor financing. Further planning data for projects in the new federal states are to be expected in the years ahead. All in all, the still high number, with a downward trend – of planned tunnelling measures in Germany explicitly reveals the problem of an ongoing investment gridlock in this country. It is to be hoped that the toll revenues from heavy goods traffic that have now become an established feature will gradually lead to the situation improving.
Technical details relating to the planned tunnels included in Table 2 are available in the relevant tables (available under http://www.stuva.de) Essential-ly they are divided up in the same manner as the statistics pertaining to tunnel projects that are in the process of being undertaken as presented in Chapter 1. The same approach was selected to identify and differentiate the individual tunnel projects. However, the letter “Z” has been added to make quite clear that the tunnel construction measure in question is a “future” one. As a consequence, no details are provided about the responsible construction company or consortium as are to be found in the statistics pertaining to current tunnel projects.
Generally speaking, as far as assessing the detailed data relating to future tunnel projects is concerned, it must be observed that alterations can occur during the planning approval or the award stages, above all, on account of special proposals, relating primarily to the tunnelling method. Various clients expressly pointed this out. Alternations can of course, also result with respect to the probable starting and completion dates for construction.
Is it also of interest for the construction industry and the consultants involved to be aware of the regions, in which the planned tunnel projects are primarily scheduled to be undertaken. Table 4 and Fig. 7 contain the relevant details split up in accordance with the federal states concerned.
3 Planned Tunnel Redevelopments
To an increasing extent, partial and complete redevelopments are scheduled for old railway tunnels. Generally speaking, such measures call for rather special organisational and logistical considerations, above all, if they have to be undertaken without disrupting train services. Recent examples of this are provided by 2 tunnels – namely the Jährodt and the Mausen-mühlen tunnels on the line along the River Nahe between Bingen and Saarbrücken . This route started operating in 1860. Fig. 2 displays details of the basic redevelopment in the Ennerich Tunnel (Lahn Valley). In the near future altogether the thorough development or profile enlargement of no less than 24 km of tunnel is scheduled. Table Section “ZGS” contains the relevant details. The identification and description of the new projects correspond with the future new construction projects to be found in Table 2.
Bibliography: see German original
1 Statistics on Tunnels under Construction 2007/08