The Galgenbuck tunnel in the region of Schaffhausen

Schaffhausen with its Munot fortress

The town of Schaffhausen is the most northerly-lying town in Switzerland and, with more than 35,000 residents, forms the centre of the similarly named Canton of Schaffhausen. It is one of the small Swiss towns to the North of the High Rhine at the border between Germany and Switzerland and to the South-East of the Randen in the Table Jura.

The landmark of Schaffhausen is the Munot. This mediaeval fortress with its pronounced circular shape was part of the town’s fortification and was built between 1564 and 1589, partially involving slave labour by the burghers of Schaffhausen.

Another tourist attraction of Schaffhausen is the Rhine Falls, located 2.5 km downstream in the district of Neuhausen am Rheinfall and Laufen-Uhwiesen. With a height of 23 m and a width of 150 m, it is one of the three largest waterfalls in Europe. At an average flowrate of the Rhine, approximately 370 m³ of water tumbles over the rocks every second and in Summer this can be up to around 600 m³ per second.

Congestion relief for the region of Schaffhausen

The A4 Autobahn connects Schaffhausen with the German Autobahn A81 in the North and with the city of Winterthur in the South. After the opening of the A4 bypass in August 1996 there was an enormous change in the traffic flow in the Schaffhausen and Neuhausen region. This subsequently led to a huge increase in the traffic load on the feeder roads to the Schaffhausen South junction, in turn causing congestion in the region around Neuhausen am Rheinfall to increase massively. Meanwhile, more than 25,000 vehicles a day were travelling along this section of road.

In 2007, the Council of the Canton of Schaffhausen presented the implementation project for the new two-lane Galgenbuck tunnel which, as a bypass route, should almost halve the traffic load in the district of Neuhausen am Rheinfall and make the Schaffhausen South junction viable in the long term. As an additional secondary effect, Neuhausen am Rheinfall would benefit from a reduction in the burden of noise and air pollution, from shorter journey times and a minimisation of accidents. The cost of constructing the new tunnel, of approximately 240 million Swiss francs, is covered in full by the Federal Government (the Swiss Confederation) as, legally speaking, this is the restructuring of a national road link.

The new Galgenbuck tunnel project

The new Galgenbuck tunnel passes under the municipality of Rheinfall in a wide arc with a rock cover of only 20 to a maximum of 70 m. The two-lane road in the tunnel runs for a total length of 1,138 m with a maximum gradient of 4.5 % from the “Engi” portal in the West to the “Bahntal” portal in the East close to the Schaffhausen South motorway junction. Once construction has started in 2011, the first stage was to complete the two tunnel portals as cut-and-cover tunnel sections, with the remaining approx. 1,060 m long tunnel section being driven as from the middle of 2013 using mining blasting techniques. Breakthrough was achieved as early as February 2016. After a little more than two years construction time, the concrete work in the tunnel was able to be concluded in July 2018 and the technical engineering and safety specialists could set about their own tasks. The commissioning of the Galgenbuck tunnel is planned for 2019.

Installation of the extinguishing water pipeline in the service duct

With the installation of the operating and safety equipment which is currently underway, the empty concrete pipes are finally being turned into a tunnel. In the service duct located beneath the carriageway, the extinguishing water pipeline with its lateral outlets to the hydrant recesses at road level is the first thing to be installed. Following that will be the installations for monitoring and controlling the tunnel. In addition, the escape gallery is incorporated into the service duct.

The pressurised water pipeline in the service duct consists of ductile iron pipes of the vonRoll ECOPUR type in nominal size DN 250. It runs for a total length of 1,060 m in alignment with the tunnel with a minimum curve radius of 500 m and is fixed to the concrete back wall and the floor of the service duct by pipe clamps. The changes of direction in the curve are accommodated by the deflectability of the push-in joints.

From the main pipeline in the service duct, lateral branch pipelines spaced a maximum distance of 150 m apart supply the seven hydrants in the road space with extinguishing water.

The branch pipelines are also constructed of ECOPUR full-protection DN 125 pipes in ductile cast iron and they run through a casing pipe above a chamber lying approximately 3 m below the hard shoulder to the hydrant connections. Dismantling the branch pipelines from the service duct is therefore possible at all times. For the installation, overhaul and maintenance of the fire hydrants, the hydrant chamber is accessible at any time via an 80 x 80 cm large entrance from the road space.

The full-protection vonRoll ECOPUR pipes are integrally coated with polyurethane (PUR) and are classified in accordance with standard EN 545 [1] as cast iron pipes with reinforced coating for use in all ambient conditions. Because of their highly resistant, pore-free PUR coating to EN 15189 [2] they can be used in all types of soils and therefore have the best protection against corrosion even in the aggressive climate of the tunnel. ECOPUR pipes have a polyurethane (PUR) lining in accordance with EN 15655 [3]. The mirror-smooth PUR lining minimises deposits and, because of extremely low friction losses (roughness k = 0.0014 mm according to SVGW W4 [4]), promotes the hydraulic performance of the extinguishing water pipeline in case of fire. In order to safely absorb the forces occurring due to internal pressure, the entire pressurised water pipeline including the hydrant branch pipelines is secured against longitudinal forces by the assemblyfriendly vonRoll HYDRO-TIGHT thrust protection system. The flexible cast iron pipe system is completed by vonRoll ECOFIT fullprotection fittings with push-in and flanged joints which are also integrally protected the with a thick epoxy coating to EN 14901 [5] and the enhanced requirements according to RAL-GZ 662 [6].

High-performance hydrants for extinguishing water supply

In order to fulfil the high requirements for fire protection, the hydrant recesses are equipped with the high-performance double-armed vonRoll HYPLUS type hydrants which can deliver a maximum output of 4,000 l per minute (at a differential pressure of 1 bar). The patented joints between the top and bottom parts of the hydrants allow stepless 360° directing of the hydrants in the narrow installation recesses in the road space of the new tunnel.

The flexible VARIO 2.0 type H2L hydrant bottom with a maximum adjustment range of 70 cm (in 5 cm increments) offers optimal flexibility in the hydrant chambers when bridging over the existing level differences. The DUO maintenance shut-off installed as standard allows later overhaul work on the hydrant under full system pressure without decommissioning the extinguishing water supply.

Full-protection valves for secure operation and simple maintenance

At the high point of the tunnel – at the extinguishing water pipeline connection in the Engi portal – vonRoll VS 5000 type shut-off valves are used as pipeline valves and for cleaning purposes. At the same time a vonRoll vent valve is arranged at this point to extract air from the extinguishing water pipeline. The extinguishing water pipeline in the service duct equipped with a VS 5000 pipeline valve at each hydrant branch pipeline and it is divided into individual sections so that, in case of maintenance work, the entire pipeline does not have to be taken out of operation. There are also cleaning and drainage connected connections installed at the same point for servicing and cleaning work.

Conclusion

The safety and security infrastructure in motorway tunnels takes first place with the tunnel operators, not least because of the devastating and catastrophic fires which have occurred in certain tunnel structures in the past.

Ductile iron pipe systems have proved their worth for extinguishing water pipelines in road tunnels for decades now and in case of fire events they are extremely reliable for delivering firefighting water. The flexibility of the sockets of ductile iron pipe systems make very flexible and efficient installation of the extinguishing water pipelines possible in the tight conditions inside the tunnel. Because of its mirror-smooth surface, the innovative lining with polyurethane avoids friction losses in the system, which in turn results in an increase in hydraulic performance when the water is drawn off. Ductile iron pipes ensure a high degree of operational security of the extinguishing water supply in challenging tunnel structures.

 

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