Tunnelling in Germany: Statistics (2012/2013), Analysis and Outlook

1 Tunnels under ­Construction

As in previous years, the STUVA also undertook a survey of current tunnelling projects in Germany at the turn of the year 2012/2013. The outcome is compiled in tabular form for the month of December 2012 and subsequently assessed. The table follows up its predecessors published for the years 1978 [2] to 2012 [3]. Only tunnels and drain/sewer structures which possess an accessible (walk-in or crawl-in) 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 m², are listed. On the other hand, small trenchless headings which, in recent years, have frequently been executed in conjunction with main drain construction, the relevant domestic connections, and also pipe-jacking operations beneath rail and road facilities, are not included.

The tables for the tunnel projects under construction at the turn of the year 2012/2013 are not listed in detail on account of their extent; however data can be obtained from STUVA’s Internet pages (//www.stuva.de" target="_blank" >www.stuva.de:http://www.stuva.de). In these tables, the numbering of the tunnel projects indicates the relationship to the data material originating from previous years. Essentially it takes the form of single or double identification letters, a two-digit sequential registration number and a two-digit annual identification number. The identification letters serve to provide a brief assessment of the planned tunnel utilisation, namely:

US Underground, urban and rapid transit rail tunnels

B Main-line rail tunnels

S Urban and trunk road tunnels

V Water and other supply tunnels

A Drain/sewer tunnels

So Miscellaneous tunnels

GS Tunnel modernisation

The identification number US 0112 therefore refers to a tunnel project with the sequential number 1 from the underground, urban and rapid transit rail tunnels sector which was included for the first time in the statistics in 2012. 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 2 or 3 years, or even more. This method of registration has proved itself in order to avoid projects being counted twice and to identify the new construction volume that was to be included. Relevant indicators relating to calculation of construction lengths and excavated volumes are accordingly contained in Table 1. In addition to the details for the turn of the year 2012/2013, the figures from the 2 previous years can also be found there for comparison.

By and large, the tunnel lists on the STUVA Internet pages provide information on the location and ultimate utilisation of the tunnels that are included, their length and cross-sections, and also the soil conditions mainly encountered. The construction method used is explained in brief and the scheduled construction time stated. As far as possible, the clients, designers and contractors are named, the last-mentioned in amendatory alphabetical order. Details of constructional or technical aspects of a special nature are also provided for many projects.

When comparing transportation tunnels with supply and disposal tunnels, information on the excavated volumes of the individual works makes it possible to estimate the actual extent of the relevant measures in a better manner than mere details relating to lengths. However, the following should be observed when comparing the excavated volume: whereas the excavated volumes for trenchless construction measures can be determined with certainty, the comparative value for cut-and-cover methods can only be obtained by subtracting the amount of soil required for refilling from the total excavated.

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 2012/2013, Fig. 1 also contains the driven length and the excavation volume in accordance with the type of tunnel utilisation shown in graphic form.

A general comparison of the figures in Table 1 again reveals a clear increase in the driven length of transportation tunnels as at the turn of the year 2012/2013, with a total of some 172 km compared with almost 139 km the previous year. Building activities tailed off slightly in the sectors underground, urban and rapid rail transport and road whereas operations in main-line construction rose considerably. Contracts awarded in conjunction with the major projects Stuttgart 21 and the new/upgraded Stuttgart–Ulm rail route made an impact here (Fig. 2).

If one considers the data relating to excavated volume, there is a length-related ratio of almost 3 : 1 as against a volume-related one of around 45 : 1 when comparing transportation tunnels on the one hand with supply and disposal facilities on the other (Fig. 1).

The question of the completeness of the data obtained from the STUVA survey from construction contractors 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, and also Deutsche Bahn AG, were requested to supply data within the scope of the 2012/2013 survey, as was the case in previous years. The Federal Ministry of Transport, Building and Urban Affairs (BMVBS) provided data for federal trunk road tunnels [4]. In a large number of cases, the responses from these authorities and from Deutsche Bahn AG resulted in important additions and corrections. At this point, a special word of thanks goes to the Federal Ministry of Transport, Building and Urban Affairs, Deutsche Bahn AG, the other authorities and clients mentioned and the architects and contractors involved, for their assistance in compiling the statistics for current tunnelling projects.

In the following, the results of the survey as of December 2012 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 explanatory notes relating to the structures to be found in ”Underground Construction in Germany 2010”, containing a large number of examples presented in both illustrated and written form are referred to [5].

This year, the main activities relating to inner-urban rail tunnelling (Table section US) took place in Cologne, where some 5.9 km of underground tunnels was under construction at the turn of the year 2012/2013. Currently some 3.7 km of urban transit tunnels are being driven in Karlsruhe. Further tunnel projects are underway in Düsseldorf (3.3 km), Berlin (2.6 km) and Stuttgart (1.7 km), Nuremberg (1.5 km), Dortmund (0.6 km) and Augsburg (0.3 km).

The length-related proportion of trenchless construction methods with regard to inner-urban rail tunnel construction amounted to 14.1 km at the end of 2012, accounting for almost 72 % of the total national construction volume for underground, urban and rapid transit rail systems (76 % the previous year). Of this total, some 12 % was accounted for by shotcreting methods (2 % the previous year) and roughly 60 % (74 % the previous year) by shield driving. Fig. 3a provides a survey of the percentages accounted for by the various tunnelling methods. In this context, the diagram in Fig. 4a shows the length-related proportion of trenchless construction methods in underground, urban and rapid transit rail construction during the last 20 years. In this diagram, the division of trenchless construction methods into shotcreting and shield driving is featured separately.

The main-line rail tunnels listed in Part B largely relate to works in conjunction with the Stuttgart 21 rail hub as well as the new-line and upgrading programme for Deutsche Bahn AG‘s high-speed routes. Of the tunnelling projects currently being implemented (a total of 110 km), almost 42 km is accounted for by the major project “Stuttgart 21 rail hub” and some 28 km by the new/upgraded Stuttgart–Ulm rail route. Furthermore, some 36 km of tunnel is being constructed on the new Ebensfeld–Erfurt line. These main-line rail tunnel projects predominantly employ underground („trenchless“) tunnelling (Fig. 4b) – 78 % using the shotcreting method (Fig. 2) and 22 % mechanised driving.

Road tunnel construction (Part S of the table), like the two other transportation tunnel sectors, has been subject to pronounced fluctuations in contracting in recent years. This becomes clearly evident from the award curve in Fig. 5 and above all, from the ­graphics pertaining to the award and length-related percentages in Fig. 6. The ratio of road tunnels built by mining means and by cut-and-cover stands at roughly 2 : 1 (Fig. 4c). As far as trenchless construction methods are concerned shotcreting in conjunction with drill+blast dominates in the majority of cases.

In the V and A sections of the table, relating to supply and disposal tunnels, only those of larger diameter – as initially explained – are listed. The smallest cross-sections dealt with are roughly 1.0 m in diameter, the largest around 3 to 4 m. All 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 in previous years. Furthermore, in compiling drain/sewer statistics, it should be pointed out that only main drains are included here. The considerably greater part accounted for by drains of smaller cross-section, mostly driven close to the surface by means of cut-and-cover, is not listed here, as this is generally not classified as tunnelling.

The distribution by federal states (Länder) of the tunnels under construction at the end of 2012 is also of interest. Table 2 and Fig. 7 provide more details of this.

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. 5 clearly shows the important influence of the DB’s new lines and displays the continuing fickleness on the part of public authorities in awarding new tunnelling contracts. With regard to main-line tunnels following a step increase in awarding contracts (mainly on account of the commission of “blocks” for the DB high-speed routes) the resultant years experienced an equally pronounced dip (Fig. 6). Currently awards are reaching a new high with regard to the activities in conjunction with the major projects “Stuttgart 21 rail hub” and new/upgraded Stuttgart-Ulm rail line. Fig. 5 also displays the average annual “completion rate”, which amounts to around 30 km for all transportation tunnels over a period of 20 years.

2 Projected Tunnels (future Requirement)

The results of the survey relating to confirmed tunnel projects and those due to be awarded in the near future are naturally of special interest to the construction industry and consultants. Table 3 shows the award period starting in 2013.

Examination of the data in Table 3 clearly indicates that the planning volume for underground, urban and rapid transit rail tunnels has further shown a slight decrease without the state awarding a substantial number of projects (Table 1). This can mainly be attributed to plans changing owing a dearth of public funds. In this context, the remaining planned volume for the city of Munich, comprising just on 22 km, is conspicuous among the projects still planned. A good 6 km of tunnel for the rapid transit system is planned for Stuttgart, in conjunction with the Stuttgart 21 project. Further tunnel construction for underground, urban and rapid transit systems, up to roughly 3 km in each case, is scheduled for Dortmund, Düsseldorf, Nuremberg and Frankfurt/Main. Regarding the planned volume of main-line rail tunnels, it should be noted that the bulk is accounted for by the approved tunnels as part of the new/upgraded Stuttgart–Ulm rail line (driven length: 30 km). A large proportion of the planning volume registered last year has now been awarded and is thus under construction (Table 1), although it should be mentioned that the actual tunnelling work for these projects has by and large still not been started.

The planned volume of projected road tunnels amounts roughly to that of the previous year. On account of the state’s requirements, the planning volume was slashed considerably last year. Around 95 % of the projects listed are in the old (western) federal states of Germany (Table 4). The measures that are being planned in the new (eastern) federal states are mainly at the preliminary planning stage and are consequently not yet sufficiently advanced to be included in the statistics. The planning in this sector is primarily being carried out in conjunction with „German Unity Projects – Road”.

The 142 km of planned road tunnels listed in Table 3 has at least generally reached the planning approval stage. This applies principally to the tunnels on federal trunk roads, i. e. those for whose construction the federal government is responsible. Further road tunnels totalling almost 80 km in length are also under consideration, and these must be added to the figures shown in Table 3. For a number of these projects, the environmental impact assessment (EIA) has already been concluded or the route alignment has been finalised. Their implementation is not yet totally certain, however, either in terms of scheduling or financing.

Technical details relating to the planned tunnels included in Table 3 can be found in the relevant tables (available from //www.stuva.de" target="_blank" >www.stuva.de:www.stuva.de). Essentially, these are structured in the same manner as the statistics on tunnel projects which are in the process of implementation, as presented in Section 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 concerning the responsible construction companies or consortium, whereas these can be found in the statistics on 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 and award stages, above all, due to special proposals, relating primarily to the tunnelling method. Various clients expressly pointed this out. Alterations can of course, also result with respect to the probable starting and completion dates for projects.

It is also of interest for the construction industry and the consultants involved to be aware of the regions for which implementation of the planned tunnel projects is mainly scheduled. Table 4 and Fig. 8 show the relevant details, categorised by federal state.

3 Tunnel Modernisation Plans

To an increasing extent, partial and complete refurbishing schemes are now being scheduled for existing rail tunnels. Generally speaking, such measures call for special organisational and logistical provisions, particularly if these projects are to be implemented without causing disruption to rail traffic [6]. Recent examples of this are provided by the complete renovation of the Frauenberg and Kupferheck tunnels on the Nahe valley line between Bingen and Saarbrücken as well as the Langenau and Hollerich tunnels on the Lahn valley line between Wetzlar and Niederlahnstein at Nassau. These lines were opened back in 1860 and 1862 respectively. In the near future, comprehensive modernisation and/or –cross-sectional enlargement of no less than 13 km of tunnel is scheduled in addition to the 4 km already accomplished. Table Section “ZGS” contains the relevant details. The identification and description of the individual projects correspond to the future new construction projects found in Table 3.