User:Ajcoxuk/Leipzig Tunnel



The City Tunnel is a railway tunnel under construction for the city-centre S-Bahn in Leipzig with two tunnels with one track in each direction. It will link the Hauptbahnhof with the two kilometer distant Bayerischer Bahnhof (which is closed for the construction period).

Construction began in July 2003. In March 2008, the first tube was structurally completed, the second in October 2008. The tunnel for the trains should be ready for the timetable change in December 2013.

Route
From South to North
 * MDR Leipzig (outside the tunnel)
 * Bayerischer Bahnhof (platform length of 140 m)
 * Wilhelm-Leuschner-Platz (platform length of 140 m)
 * Markt (platform length of 140 m)
 * Leipzig Hauptbahnhof (platform length of 215 m. Option to extend in a northerly direction to a length of 400 m); 800 Meter long ramps
 * Leipzig Nord/Berliner Brücke (originally Theresienstraße, outside the tunnel)

In addition to the four underground stations of the City Tunnel, the shells of the new stations Leipzig MDR und Leipzig Nord - Berliner Brücke were completed in January 2011.

The northern ramp to the entrance of the tunnel is 600 meters long and has a slope of 40 ‰

Projected operating schedule
It is planned that each hour and in each direction, there will be up to ten S-Bahn, two regional and one express trains. (as of July 2007)

The new S-Bahn network (from December 2013) was described in August 2008 as follows :


 * S 1: Leipzig-Miltitzer Allee –Leipzig-Gohlis –Hauptbahnhof –Bayerischer Bahnhof –Leipzig-Stötteritz –Wurzen,
 * S 2: Bitterfeld –Delitzsch –Leipzig-Messe –Hauptbahnhof –~ Bayerischer Bahnhof –Leipzig-Connewitz –Gaschwitz,
 * S 3: Halle-Nietleben –Halle (Saale) –Schkeuditz –Leipzig-Gohlis –Hauptbahnhof –Bayerischer Bahnhof –Leipzig-Stötteritz –Wurzen –Oschatz,
 * S 4: Hoyerswerda –Falkenberg (Elster)  –Eilenburg –Taucha –Hauptbahnhof –Bayerischer Bahnhof –Leipzig-Connewitz –Gaschwitz –Borna –Geithain,
 * S 5: Halle (Saale) –Flughafen Leipzig-Halle –Leipzig-Messe –Hauptbahnhof –Bayerischer Bahnhof –Leipzig-Connewitz –Gaschwitz –Altenburg –Zwickau (run as S 5 und Express-S-Bahn S 5X)

As planned in the summer of 2007, the S-1 should run every 20-minutes, the four other lines with intervals of between 30 minutes and 120 minutes.

Before construction, capacity was limited to eleven S-Bahn trains, two regional express trains and one express train per hour in each direction. Critics doubt though that a more appropriate mixed mode of regional and long-distance traffic in the tunnel is possible.

Background
A connection of the Dresdner Bahnhof (on the territory of the later Leipzig Hauptbahnhof) with the Bayerischer Bahnhof was considered for the first time in 1892. The implementation was planned as an Underground Railway, which would run parallel to the two mainline tracks from Borsdorf via the Hauptbahnhof and the Bayerischer Bahnhof and on to Connewitz and Gaschwitz. It would be powered by a Third Rail system. During the construction of the main station (started in 1909), between 1913 and 1914 an entrance ramp was built from the direction of Dresden with a length of 140 meters with a 675 meters long tunnel under part of the station. The tunnel ended 8.5 meters in front of the station building under the inner city ring road. Beneath the crossing tramlines and the current bus station, underground platforms 22 and 23 of some 40 meters in length were built. An extension below the ring road was planned and prepared a length of 100 meters is already available. The construction work was suspended during First World War and was not resumed thereafter.

During World War II the tunnel and underground stop were converted to provide  Air-raid shelters. During the bombing raid on Leipzig on July 7, 1944, there were two explosions that destroyed the tunnel at two places and thus divided it into three parts. Many people were killed. During reconstruction of the main station, the area around the second impact point was walled-in, and the platform under the east portico coverted into the DEFA-Zeitkino Cinema and was used for this purpose until 1992. During the main railway station redevelopment in the years 1995 to 2000, parts of the tunnels under the station were demolished. The tunnel below the apron and the first few meters of the station hall were closed, but remained preserved.

Shortly after the Second World War in 1946 planning for an underground city crossing restarted. In order to accommodate the entrance of the tunnel, redevelopment work at the corner of Windmühlen- and Grünewaldstraße was delayed. That would allow a curve to be built with a suitable arc for long distance trains. The plan foresaw an S-Bahn route and a mainline railway tunnel in the direction of Munich. The latter was dropped a few years later due to the division of Germany. Until 1967 three variants for the S-Bahn tunnel were developed, which together with the current tunnel, were no longer in the direction of the Dresden route, but rather in the direction of Magdeburg and Berlin. Stations were planned under the Western Hall of the Hauptbahnhof and under the city-centre Markt. Due to the expected high financial and technical effort, the plans were not realized before the end of the DDR.

Planning
The tunnel will be used by all trains of the Leipzig S-Bahn. It is hoped that the shorter intervals and faster connections will allow public transportation to accommodate additional passengers and thus road traffic in the city will be relieved. In addition, it will bring more passengers directly from the Leipzig Hauptbahnhof by rail to the city centre and converts the terminus to a partial through station. Additionally, it is planned to run one intercity train per hour and direction through the tunnel. However, the electrified route currently ends in Reichenbach im Vogtland. Therefore the states of Saxony and Bavaria, the Federal Government and DB are planning for the continuation of rail electrification first to Hof, and later on to Regensburg and Nuremberg. The preliminary planning for the first section is currently taking place and construction is scheduled to take place until 2012. The route will be operated by S-Bahn Germany GmbH, a subsidiary of Deutsche Bahn. Between Reichenbach and Herlasgrün the track is completed. In 2012 the electrified route will be extended Plauen. On the Frankish side of the border in Bavaria, the work between Gutenfürst and Hofside has already progressed well, with only the Gutenfürst and Hof stations remaining to be electrified.

Early in 2002, the Saxony State Government gave support for the implementation of the City Tunnel. On 18 March 2003, they approved the project formally.

On 6 January 2010 it was announced by a correction notice to the tender for the Leipzig train network, that the start of the new train service would be delayed for another year until the timetable change in December 2013.

Costs
The framework agreement of 2002 provided for the total project cost at € 571.62 million, financed by funds from the State of Saxony (€182.02 million), the European Union (ERDF program, €168.73 million), the federal government (€191.73 million), Deutsche Bahn (16.36 million) and the City of Leipzig (12.78 million Euros). This agreement covered many issues including the refurbishment of the stations and the electrification of several sections.

At the end of 2001 it was expected that the total cost would amount to 1.04 billion DM. DM 240 million would come from the EU Structural Fund. Already additional security measures had lead to additional costs.

In 2006, the ERDF funding allocated at the end of the funding period was reduced from 168.73 to 127.59. million Euro, which have now been all spent (as of February 2011). For the current 2007-2013 funding period, a further follow-up funding application was submitted, but was not approved (February 2011).

The builder's representatives DEGES expected in December 2006 the costs to amount to 585 million Euros. A risk analysis by Deutsche Bahn saw at that time possible additional costs of up to 73 million Euros. In December 2007, the additional cost was estimated at 133 million Euros, so that the expected total cost will be 705 million €. . In October 2008 it was announced that the commissioning is expected to be delayed until the end of 2012, as there are problems in the area of ​the Hauptbahnhof with the Underground route and delays with the approval of the network extensive work.

After the estimated total costs had risen by the end of November 2009 to 893 million Euro, the Saxonian State Auditors reviewed the project. At the end of February 2010, a further cost increase to 960 million Euros was announced. This, according to the Sachsen State remains the expected total cost (As of September 2010).

The Federal share provided is, in line with the framework agreement, limited to 191.73 million Euro (plus Wage and price increases). With the exception of the indexation component, the federal share has already been used in full (as at September 2010). The additional costs are mainly supported by the Free State of Saxony and the city of Leipzig, and to a lesser extent, the German Railways.

The project has been criticized by various parties because of the high construction costs for the relatively lightly used Leipzig S-Bahn, the limited usability for long-haul and the long lasting construction work in the city center with its associated obstruction and loss of revenue.

Construction
When constructing the Leipzig Central Station, the Saxon State Railway had planned for a tunnel to Bayerischer Bahnhof. In the years 1913 and 1915, a 710 m long section below the tracks 22 and 23 was created before the work came to a halt due to the First World War and a lack of funds. As part of the modernization of the railway station this tunnel section was excavated in 1997 and demolished within the station hall areal.

In the early 1990s the existing plans for a mass transit tunnel through downtown Leipzig which had existed for decades and the results of the planning in 1995 were presented. In 1996 the German Railways and the Free State of Saxony, expressed their support for the project. In the same year the Free State, city planning and DB AG Company founded the planning company S-Bahn Tunnel Leipzig GmbH. Following a cost-benefit analysis in 1998, the planning application was issued. In 2000 planning approval was issued.

In the fall of 2001 Saxony invited DB to be the project owner of the City Tunnel. The company should therefore build the tunnel under their own financial risk. After the completion of a financing agreement in the spring of 2002 the invitation of the individual building sub-contracts took place.

On July 9, 2003, the building begun with the official groundbreaking. At the start of construction the start of tunnel operation was planned for late 2009. At first, there were mainly ground investigations and the relocation of services. The construction of the underground stations began in early 2005.

At the end of March 2005 preparations for construction with the platform area of the main station began. This space was created for the following excavation. In December 2006, the construction of the ramps at the main station was interrupted after cracks were found in neighbouring station buildings. Between 17th February and 25th March 2007 two auxiliary bridges of 105 meters were built as part of the construction in the Hauptbahnhof. In addition 1,400 meters of track and eight points were rebuilt.

On 11 January 2007 the tunnel boring machine called Leonie began (with a ceremony at the Bayerischer Bahnhof) to symbolically bore the first tunnel. The tunnel's godmother is Angelika Meeth-Milbradt, wife of then Prime Minister of Saxony Georg Milbradt The excavation began on January 15, 2007 and on March 10, 2008 reached the railway station, so completing the first bore. After the return of the tunnel boring machine to Bayerischer Bahnhof in late March 2008, the excavation began of the second bore on 9 May 2008. On 31 October 2008, the tunnel boring of the tunnel ended with the completion of the second bore.

Until the expected opening in December 2013 followed the interior fitting-out of the tunnel and railway stations. In mid-February 2009, the contract to development the five stations was advertised throughout Europe. The contract will run from February 2010 to November 2011. The tender has been divided between two companies.

Construction Technique
The two 1438-meter-long tunnels were largely dug using a 65-meter Tunnel Boring Machines. The start of the tunnel boring machine work was in the pit at Bayerischen Bahnhof, from where they worked towards the Hauptbahnhof. There it was dismantled and re-built AT Bayerischen Bahnhof, after which it started a second time. At Bayerischen Bahnhof and at all other stops between, three Einphasenschlitzwände  were constructed. The suspension  was mixed with cement and hardened in the slot. This mass then formed a waterproof wall through which the tunnel boring machines could run without the surrounding water and rock penetrating.

The tunnel has an excavated diameter of nine meters and was driven by a fluid-based plate. This generates a positive pressure that prevented the ingress of water and rock into the tunnel. Using this approach, however, there is a danger that the pressure is lost due to old water wells with the collapse of the ground in front of the tunnel boring machine. The coverage varies from eight to sixteen metres. The shortest distance between the building foundation and tunnel roof is under the Petersbogen underground carpark at 2.20 meters. The tunnel was in the ground water at a pressure altitude of approximately 16 meters to the bottom of the tunnel. The lining of the tunnel was carried out with seven re-enforced concrete segments, which form a tunnel ring, which are 40 cm thick and a keystone. For the two tunnels approximately 13 000 segments were required.

When tunneling in soft ground it is expected that the tunnel will sag due to soil loss (sagging of the soil after tunneling or mining operations) which cannot be avoided completely. The lower tray is about 60 to 80 meters wide. The depth depends (among other things) on the type of coverage, the shear strength of the soil and the overlay. A maximal deviation of 20 to 30 mm is anticipated after the second tunnel bore. All buildings that are in the tunnel route and affected, have been examined in advance. (Drilling, geotechnical investigation, Bauakteneinsicht)

The crossing under the main railway station is not done by the tunnel boring machine, but by manual digging. There were extensive measures to secure the main railway station against the builting work. The plans was to freeze the pit edge and drive through this frozen ground under the station. The plans include two tunnel excavations with a diameter of 2.40 meters using compressed air and a cover plate. From this side vertical tubes were inserted to freeze the ground were built and the ground was frozen into a waterproof layer.

Compensation grouting process (CGP)
In order to prevent settlement of more than 30 millimeters at the tunnel Verpressschächte have been built. Of these, were generated as necessary, heave of the soil by high-pressure injections. Partially, the soil was already previously raised by a few millimeters in order to reduce the final setting depth. In the Peter street about 250 meters long supply tunnel from GDR times was used for the injection. It begins and ends at St. Peter's bow on the market. All the buildings in St Peter's Street can be achieved. Of the Verpressschächten holes were made, terminating at the buildings. These holes are provided as needed and then with Verpressrohren Verpressgut is introduced under high pressure. The Verpressgut is composed of binder and water.

Here, the Compensations-grouting process  was applied. For it are in different places pits, the so-called CGV-shafts arranged. Overall, the method consists of four phases. First, dug wells or pits at appropriate points, be created from which horizontal wells. This can be, according to a length of up to 70 meters. In the horizontal drilling valve tubes are installed. Through these tubes is finally pressed cement into the ground. This will start the actual backup of the building. The soil is compacted and any gaps there may be filled.

In a second phase is in some places the land controlled by another pumping increased. The elevation is to compensate for reductions occurring under certain circumstances during the tunneling. At the time the bore of the City Tunnel tubes the buildings in the vicinity of the bore be monitored. With precise technique smallest movements are registered. Accurate to 0.25 millimeters, the units can monitor the structural elements of buildings. For the case that the uplift not the actually occurring reduction can compensate, further cement is pressed into the ground and kept the buildings at a constant level.

Even after the completion of the excavation, the houses are still monitored regularly and, if carried further injections.

Literature

 * Kurt Ackermann, Andreas Glowienka, Reinhard W. Heinemann u. a.: City-Tunnel Leipzig. Chronik einer Eisenbahnverbindung vom 19. bis zum 21. Jahrhundert. Strom & Strom, Leipzig 2004, ISBN 3-9807618-4-3
 * Horst Fechner: City-Tunnel Leipzig −Vom Reißbrett zur Realisierung. In: Der Eisenbahningenieur. Eurailpress Tetzlaff-Hestra, Hamburg 2005,7, S. 5−2.
 * DB ProjektBau GmbH (Hrsg.): Infrastrukturprojekte 2010. Bauen bei der Deutschen Bahn. Eurailpress-Verlag, Hamburg 2010, ISBN 978-3-7771-0414-0, S. 132–46.
 * DB ProjektBau GmbH (ed.): infrastructure projects 2010th Building on the German Railroad.