The Katzenberg Tunnel is a railway tunnel on the Karlsruhe–Basel high-speed railway that opened in December 2012. The tunnel was built to increase the capacity and speed of the Mannheim–Karlsruhe–Basel railway (Rhine Valley Railway, or Rheintalbahn in German) and was built to remove the freight traffic from the towns on the old line. The two parallel, single-track tunnels, which can be passed at up to 250 km/h, extend from Bad Bellingen to Efringen-Kirchen With a length of 9,385 m, it is the third longest tunnel after the Landrücken Tunnel and the Münden Tunnel and the longest twin-bore tunnel in Germany.
The reduction in journey times for long-distance passenger trains between Freiburg and Basel initially amounts to two minutes. After the completion of the entire section of line, the journey time will be around 15 minutes shorter. At night a few freight trains and during the daytime many freight trains are routed through the Katzenberg Tunnel.
The tunnel and its connection to the existing network cost a total of approximately €610 million. The line was cleared for operations by the Federal Railway Authority (Eisenbahn-Bundesamt) on 4 December 2012. The opening ceremony took place on the same day. Regular operations began on 9 December 2012.
Description
The tunnel is part of a 17.6 km-long section of new line (brochure) and is situated between kilometres 245.410 and 254.829 of the old line (DB network route number 4280).
The tunnel is named after the Katzenberg (a mountain with a height of ), which lies about 1.2 km east-northeast of Wintersweiler and a few hundred metres east of the tunnel. It passes through the periphery of the Markgräfler Hügelland (Markgräflerland high lands) (twelve page brochure with data from April of 2006) The north portal is at Bad Bellingen and the south portal is at Efringen-Kirchen. In its course, the tunnel passes through the localities of Hertingen and Bamlach (line km 248), Rheinweiler (km 249), Blansingen and Welmlingen (km 251), Mappach (km 252), Wintersweiler (km 253) and Efringen and Efringen-Kirchen (km 254).
With a design speed of 300 km/h, the tunnels are operated at 250 km/h. The route of the tunnel runs is straight along almost its entire length, although in the northern part of the route there is a curve with a length of 400 metres and a radius of approximately 4,000 m.
The standard distance between the two tunnels (track centres) is 26 m. (12-page brochure) The axis of the track lies 62 cm off-centre to create space on one side for an escape route. The two tunnels are connected by about 19 cross-passages at a spacing of approximately 500 m.
At the south portal there is an approximately four kilometre-long above-ground section, connecting with the main line of the Rhine Valley Railway at Haltingen (kilometre 264). A three kilometre-long above-ground section connects the northern portal with the main line at the station of Schliengen (km 243).
Altitude
The north and south portals are on almost the same level (around above sea level). The tunnels rise slightly towards their centre, which are about 16 m higher. The north portal is 253.73 m above sea level and the tunnels then initially ascend on a gradient of 0.1% for about 2,433.5 m and towards the centre, the gradient rises at 0.54% to the 3,280.8 m point. At this point, the tunnels reach their highest point of 269.43 m. To improve the ventilation, a 65 m deep ventilation shaft was built above the highest point of both bores near Gupf. They have internal diameters of six metres and their shafts end approximately three metres above ground level. They are protected with fencing and a safety gate. The tunnels then descend over a length of 4,964.8 m on a gradient of 0.35% to the south portal, which is at an elevation of 256.84 m, which is about three metres above the north portal.
The depth of cover over the tunnel is generally between 25 m and 110 m; the shallowest cover of 23 m is below Bundesstraße 3 (federal highway 3) near the 250.7 km point of the line and the deepest cover is at a point southeast of Bad Bellingen.
Geology
The tunnel mostly passes through the soft strata of the foothills on the edge of the Upper Rhine Plain, which have been subjected to different degrees of weathering. It was driven mostly through tertiary sedimentary rocks such as clay, marl and limestone, sometimes also sandstone. An exception is an approximately 800 m-long section at the southern half of the route that was drilled mainly through a form of Jurassic corallian limestone called Massenkalk.
The tunnel runs continuously, up to 90 m, below the water table.
History
The original double-track line presented an obstacle to high-speed long-distance passenger transport because it followed the western edge of a steep ridge called the Isteiner Klotz and can only be operated at comparatively low speed due to the numerous curves in this area. So the maximum speed is 100 km/h at Bad Bellingen, 70 km/h at Rheinweiler, 80 km/h in three short tunnels near Istein and 120 km/h in Efringen-Kirchen. The original line is also about 3.8 km longer than the new line through the mountain.
Planning
Four route alternatives were presented as sketch plans for the planned line in 1974. The municipality of Efringen-Kirchen proposed a route through Alsace in 1978. In 1979, the director of the Karlsruhe division of the Deutsche Bundesbahn, Zimmermann suggested an upgraded line between Bad Bellingen and Istein with three new tunnels for speeds of 160 to 200 km/h.
In the early 1980s, different options for the section between Schliengen and Eimeldingen were discussed: "Rhine foreland option" (Rheinvorlandvariante), a route that ran above ground and largely just to the east of the Rhine, had a top speed of 200 km/h and had substantial effects on residences. In addition, two options (Engetal—Enge valley—and Katzenberg) with tunnels up to 8 km long were developed. In addition, there was the "Zimmermann option", which involved the upgrading of the existing line. The Rhine foreland option, initially preferred by the Deutsche Bundesbahn, was subject to many different criticisms in the region. The Katzenberg tunnel option that was ultimately built was developed between 1977 and 1981 by the local engineer Albert Schmidt and his staff at their own expense. The proposal was taken up by former project manager Ernst Krittian.
The planning approval procedure for the Schliengen–Basel section, to which the tunnel belongs, was conducted by the council of the Freiburg region from 1987 and compared the Katzenberg and the Rhine foreland options with each other. In the same year, 40 holes were sunk between Efringen-Kirchen and Schliengen to explore the subsoil. Some holes were up to 140 m deep. In the planning decision of 24 February 1989, the Rhine foreland option was rejected and the Katzenberg option was preferred. The Katzenberg option was identified as the most environmentally friendly and economical solution according to information supplied by Deutsche Bahn. It was also planned to build the new line through Eimeldingen below ground level. During the construction of Autobahn 98 an abutment was built for a railway bridge. In 2002, it was finally decided not to build the line in a cutting, but to equip it with noise barriers instead, therefore, the abutments had to be demolished.
The project design of the 1980s had a twin-track section with both tracks in one tunnel. It was decided to use GPS for measurements carried out in late 1988 during the preliminary investigations. Because the GPS was not yet fully operational, it could only be used between 9 pm and midnight when there were sufficient satellites high enough above the horizon: even so the time required for the measurements was reduced by about three weeks from what would have been required using normal methods to nine days. During the planning process in early 1989 geological and hydrological investigations were already under way.
Initially it was planned that the new line to the southern portal of the tunnel would be covered for 400 metres. These plans were dropped in 1998 due to budget constraints; this was estimated to save about ten million marks. The total projected cost of the Katzenberg Tunnel at this time was 1.3 billion marks.
Due to a lack of committed funding, planning work was interrupted from 1990 to 1996. The planning approval for section 9, to which the tunnel belongs, was divided into three sections. The tunnel was assigned to section 9.1 of the planning work, which resumed and was completed in 1997. The plans were discussed with advisory bodies from the spring of 1998 and in the affected communities from the autumn of 1998.
In response to the changing specifications of the Federal Railway Authority (Eisenbahn-Bundesamt) for fire and disaster control, two single-track tunnels were now planned. The distance to a "safe area" (cross-passage or tunnel portal) could not exceed 500 metres and the two-tube tunnel would also need to be traffickable by road vehicles.
Due to changes in the Deutsche Bahn regulations and as a result of experience, the bores also could not be built with a drainage channel but were designed to cope with an expected water pressure equivalent to a water column of up to 90 m. This led to the adoption of a circular profile as an economic solution, which made the use of tunnelling machines possible. The preliminary design for the tender was for tunneling using tunnelling machines or shotcrete as alternatives.
The planning approval process ended on 22 November 2002. The use of tunnelling machines and shotcrete were approved in the same way. Circular cross-sections were provided for both methods. The shotcrete method would have involved an excavation from both portals and from an intermediate point, while a tunnelling machine would have been launched from the south portal.
The neighbouring municipalities initiated legal action against the planning decision; this included a demand that the line in Bad Bellingen be moved to the east.
As neither tunnelling method was technically much superior to the other, tenders were called for both methods. Four bidders submitted tenders, the highest tender was 21.1 percent higher than the lowest tender. Three of the four bidders offered a shotcrete as well as a tunnelling machine solution, which in each case was less expensive than the shotcrete solution. The contract for the construction of the tunnel, was finally awarded after several rounds of negotiations on 31 July 2003 to a consortium called ARGE Katzenbergtunnel. It was led by Ed. Züblin AG (Stuttgart) and the commercial management was provided by Wayss & Freytag (Stuttgart). Other important participants were the companies of Marti Tunnelbau AG (Bern, Switzerland) and Jäger Bau GmbH (Schruns, Austria). In addition, up to 123 subcontractors were involved in the construction of the project.
When the contract was awarded, the start of construction was expected in mid 2004 and completion was expected in 2007.
Herrenknecht AG (Schwanau) was responsible for the delivery of the two tunnel boring machines (TBM). They used earth pressure shields that used excavated material to support the tunnel faces. In addition to economic considerations, the use of tunnel boring machines was also due to the generally soft strata (which could not support the tunnel walls) involved, which required tunnelling in small increments with the immediate erection of supports and lining with concrete. Due to the water pressure, the circular cross-section created by the TBM was the optimum shape for a tunnel. The price for each machine was €17 million plus €3 million for transport costs. The estimated cost of TBM tunnelling was 15 per cent below those of drilling and blasting.