Tunnelling in Germany: Statistics (2014/2015), Analysis and Outlook

For more than 35 years the STUVA has carried out a survey of tunnelling in Germany prompted by a corresponding request by the International Tunnelling and Underground Space Association [1].

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 2014/2015. The outcome is compiled in tabular form for the month of December 2014 and subsequently assessed. The table follows up its predecessors published for the years 1978 [2] to 2014 [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 1000 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 2014/2015 are not listed in detail on account of their extent; however data can be obtained from STUVA’s Internet pages [4]. 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 0114 therefore refers to a tunnel project with the sequential number 1 from the Underground, urban and rapid transit tunnels sector which was included for the first time in the statistics in 2014. 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 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. As a result, Table 1 contains the total construction volume as well as the construction volume collated during the year of the report set in brackets. In addition to the details for the turn of the year 2014/2015, the figures from the two 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 utilization 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. 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 schemes 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 2014/2015, 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 reveals a slight tailing off in the driven length of transportation tunnels as at the turn of the year 2014/2015, with a total of some 169 km compared with almost 176 km the previous year. Whereas building activities in the sectors Underground, urban and rapid transport and road revived, operations in main-line construction diminished.

If one considers the data relating to excavated volume, there is a length-related ratio of almost 2:1 as against a volume-related one of around 37:1 when comparing transportation tunnels on the one hand with supply and disposal tunnels on the other (please also see Fig. 1).

The question of the completeness of the data obtained from the STUVA survey from 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 2014/2015 survey, as was the case in previous years. The Federal Ministry of Transport and Digital Infrastructure (BMVI) provided data for federal trunk road tunnels [5]. 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 and Digital Infrastructure, Deutsche Bahn AG, the other authorities and clients mentioned and the planning agencies 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 2014 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, please refer to 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 [6].

This year, the main activities relating to inner-urban rail tunnelling (Table section US) took place in Stuttgart, Düsseldorf and Karlsruhe, where in each case some 3.5 km of urban and rapid transit tunnels were under construction at the turn of the year 2014/2015. Roughly 2.6 km of Underground tunnels were driven in Berlin, around 2.2 km in Nuremberg. Further tunnel projects amounting to less than 2 km are underway in Dortmund and Hamburg.
The length-related proportion of trenchless construction methods with regard to inner-urban rail tunnel construction amounted to 10.4 km at the end of 2014, accounting for about 64 % of the total national construction volume for Underground, urban and rapid transit rail systems (62 % the previous year). Of this total, almost 25 % was accounted for by shotcreting methods (22 % the previous year) and roughly 39 % (40 % 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 the various construction methods in Underground, urban and rapid transit rail construction during the last 20 years.

The main-line rail tunnels listed in Part B largely relate to works in conjunction with tunnelling projects in the Greater Stuttgart 21 area (Fig. 2). Of the tunnelling projects currently being implemented (a total of 105 km), almost 46 km are accounted for by the major project “Stuttgart 21 rail hub” and some 41 km by the new Wendlingen–Ulm rail route. In each case, some 8 km of tunnel are being produced in conjunction with the upgraded Hanau–Nantebach line and the upgraded/new Karlsruhe–Basle section. The tunnels on the new Ebensfeld–Erfurt line have for the most part been completed in their carcass state so that they drop out of these statistics, although the route itself is yet to become operational. These main-line rail tunnel projects predominantly employ the shotcreting method (60 %) with TBMs used for a further 35 % of the excavated volume (Fig. 4b).

Road tunnel construction (Part S of the table), like the two other transportation tunnel sectors, has been subject to pronounced contracting fluctuations in recent years. This becomes clearly evident from the award curve in Fig. 5 and above all, from the graphics pertaining to the length-related percentages of the awarded projects in Fig. 6. The ratio of road tunnels built by mining techniques and by cut-and-cover stands at roughly 3:1 (please see Fig. 4c). In this connection, shotcreting predominates in the majority of cases as far as mined tunnels are concerned.

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 m in diameter, the largest around 3–4 m. All the supply and disposal tunnels processed 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 collectors 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.

Table 2 and Fig. 7 provide details of the regional distribution of ongoing tunnelling projects. Around 90 % of the volume of tunnels being built is accounted for by the three federal states of Baden-Württemberg, Bavaria and Hesse.

If one compares the newly obtained driven lengths and excavated volumes at the turn of the year for transportation tunnels based on the statistics of recent years, this provides a revealing picture of how contracts are awarded. Fig. 5 clearly shows the important influence of the DB’s upgraded/new lines and displays the continuing fickleness on the part of public authorities in awarding new contracts. With regard to main-line tunnels, following a steep increase in awarding contracts (mainly on account of the commissioning of “blocks” for the DB high-speed routes) the resultant years experienced an equally pronounced dip (please see 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 the new Wendlingen–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 Planned Tunnelling Projects (Future Requirements)

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 2015.

Examination of the data in Table 3 clearly indicates that the planning volume for transportation tunnels has shown a further slight decrease. There has been a considerable increase in the number of Underground, urban and rapid transit tunnels without the state actually commissioning a substantial number of projects (please also see Table 1). This can mainly be attributed to the dearth of public funds.

In this context, the remaining planned volume for the city of Munich, comprising just about 30 km, is conspicuous among the projects still planned. Around 6.5 km of tunnel are planned for urban transportation projects in Frankfurt am Main. Further tunnel construction schemes, albeit accounting for less than 3 km in each case, are scheduled for the cities of Stuttgart, Nuremberg, Hamburg, Berlin, Düsseldorf and Dortmund.

Regarding the planned volume of main-line rail tunnels, it should be noted that the bulk is accounted for by the tunnels approved for the new Wendlingen-Ulm rail line (driven length: 18 km). Some 8 km of tunnel are planned in conjunction with the new Rhine/Main – Rhine/Neckar route and the upgraded Nuremberg–Ebensfelde section. A further 5 km of main-line tunnel are still to be awarded for the Stuttgart 21 rail hub project.

The planned volume of projected road tunnels has again decreased slightly, which can mainly be attributed to the lack of commissions (see Table 1). On account of the German state’s planning requirements, the scheduled volume fell considerably in recent years.

The almost 118 km of planned road tunnels listed in Table 3 have 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. 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 online in the relevant detailed tables [4]. 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 scheme in question is a “future” one. As a consequence, no details are provided concerning the responsible construction companies, 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 Modernization Plans

To an increasing extent, partial and complete refurbishing schemes are now being scheduled for old rail tunnels in the years ahead. Generally speaking, such measures call for special organizational and logistical provisions, particularly if these projects are to be implemented without causing disruption to rail traffic [7]. 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 originally opened in 1860 and 1862 respectively. In the near future, comprehensive modernisation and/or cross-sectional enlargement of some 9 km of tunnel is scheduled in addition to the around 6 km already accomplished.

Refurbishing and retrofitting is increasingly becoming more essential for road tunnels as well. Often the aim is to improve safety in technical terms, by subsequently adding an evacuation or rescue tunnel parallel to the existing bore [8]. At the time of the survey roughly 3 km of road tunnel were in the process of being redeveloped or retrofitted. Modernization or retrofitting of a further 5 km or so of road tunnel has been definitely planned. Details on ongoing renovation schemes are compiled in the table section “GS” – or “ZGS” for future renovations – of STUVA’s online tables.

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