HR and ALSTOM to build automatic train control system for Betuweroute
The Betuweroute is a 160km long double-track freight railway. It is the largest infrastructure project in the Netherlands. Construction officially started on 3 June 1997 and, on its completion in 2005, it will link the Mainport Rotterdam with Zevenaar on the Dutch/German border. By the year 2010, it is predicted that up to 10 trains an hour, travelling at an average speed of 100 km per hour, will use the line. This railway forms part of the Dutch implementation of the European policy for an integrated freight transport system. The Dutch approach to this policy assumes that all of the available means of transport - road, rail and water - should be used and that after 2010, a minimum of 60 million metric tons of freight should be carried by rail each year.
For economic and environmental reasons six tunnels are included in the crossing-free route. Three of these tunnels are bored, the "Botlek Tunnel", which is the first bored railway tunnel in the Netherlands, the "Sophia Rail Tunnel" at Papendrecht and the "Pannerdensch Canal Tunnel" at Zevenaar. These tunnels are discussed below. However, they share some common design features.
Operational and safety features
The tunnels are designed for double-stacked trains, clearance specifications have been modified and kV power will be supplied from overhead lines. The maximum gradient in the tunnels will be 2.5%. Safety had a major influence on the design. Some aspects are that the tracks will be laid in a ballast bed with derailment guidance, there will be no switches (points) in the tunnels, cross-passages will be excavated every 600 m, an emergency walkway will be included and a longitudinal ventilation system will be installed for use in emergencies. Major safety features are a sprinkler system that is designed to stop LNG (Liquefied Natural Gas) tankers exploding in the event of an accident and heat resistant cladding that will protect the tunnel interior for two hours.
First bored rail tunnel in Rotterdam port area
The Botlek Rail Tunnel is the first bored rail tunnel in the Netherlands, it is part of the Harbour Railway Line that runs through the Rotterdam port area. This line is the starting point of the Betuweroute and is planned to be operational in the first quarter of 2002. The tunnel, enclosed by the piers of the existing railway bridge, runs under the Oude Maas river at a depth of 32.5 m. It must negotiate several other obstacles, including a dense network of pipes and cables, a utility tunnel for cables and pipelines and two local roads. The tunnel has an entire length of 3065 m, 1835 metres of which is a twin tube tunnel. These tubes have an internal and external diameter of 8.65 m and 9.45 m respectively.
EPB - A first in the Netherlands
The tubes for the Botlek Rail tunnel will be bored using an Earth Pressure Balance (EPB) boring machine. This is the first time that this type of machine will be used in the soft Dutch soil. There are several reasons for using the EPB method, one of which is that it fits in nicely with the diverse composition of the soil (sand, clay and peat) along the trajectory. EPB does not require a soil separation installation, which is an advantage, because of the extremely restricted working space. Another consideration is that EPB requires less ground covering, which reduces the problem of height differences during operation.
New method, old technique
The method for removing excavated earth from the working chamber is new. The flow is controlled by a combination of a screw conveyor, two bulk pumps (when necessary), a conveyor belt and a hydraulic slurry circuit. The slurry system was chosen because it is typically Dutch, it is used extensively in the dredging industry. The advantage of this system over the classical slurry shield is that bentonite is not used in the working chamber. Cost reductions will therefore result from not having to separate bentonite from the soil and from a reduction in environmental problems.
High-tech for a long safe life
The tunnel has a design life of 100 years, which means that the technological aspects of the concrete must of a high standard. Quality control measures are in place to guarantee the dimensions and fit of the segments during production. In addition, special care must be taken to avoid damaging the segments when they are positioned and when the machine advances.
The Sophia rail tunnel: the longest tunnel along the Betuweroute
The Sophia Rail Tunnel, named after the Sophia Polder (an area of reclaimed ground) under which the tunnel runs, is 8 km long. It runs from Kijfhoek, the largest railway yard in the Netherlands, to Papendrecht, southeast of Rotterdam. The expected completion date is 2003. Its route passes under the Noord and Rietbaan waterways, which are branches of the Rhine river, various local authority areas, a sports facility, two motorways, various local roads, main flood embankments, the Sophia Polder and a dual 42-inch gas pipeline.
The slurry shield
The western approach consists of an open cut tunnel, 1635 m long, followed by a 235 m long cut-and-cover tunnel. The tunnel then diverts into two single track tubes, 9.5 m in diameter and 4.240 m long. These tubes will be bored by a slurry shield type TBM, which will use a bentonite-water mix. The tubes will be lined with concrete rings consisting of seven segments and a keystone, all of which are 0.4 m thick. The eastern tunnel approach is a 1915 m long cut-and-cover tunnel. Approximately every 600 m, cross-passages are excavated in the bored tunnel. The soil conditions are typical of this part of the Netherlands, a mixture of soft silt clay, peat, medium dense sand and silt and sandy clay.
To avoid the costs and complexity of deep construction shafts, the bored tunnel has a shallow start, partly in the holocene clay level. Major soil improvements were required in this area. The improvement method chosen was to replace the clay by compacted sand. This increased the downward force to counteract the tunnel lifting and also provided homogenous boring conditions.
Because the tunnel runs under main flood embankments, special precautions had to be taken to prevent the tunnel becoming a risk of flooding. The major risk was determined to be a failure of a flood embankment, due to an accident in one of the tunnels. To counter this risk the tunnel is locally reinforced under the embankments. The tunnel is also fitted with gates at each end to prevent water from one flooded polder flooding the other.
The Pannerdensch canal tunnel under area of natural beauty
The third bored tunnel on the Betuweroute is the Pannerdensch Canal Tunnel, which is located in the east of the Netherlands close to Arnhem and 10 km from the German border. The tunnel should be completed in 2003.
The tunnel runs under the Pannerdensch Canal, a branch of the Rhine river. Initially, a bridge was planned to carry this section of the Betuweroute, however, the area concerned is an area of natural beauty and after fierce opposition, the decision was taken to build a tunnel.
The choice of tunnel
When considering the type of tunnel that would be constructed, three designs were considered: a concrete immersed type, a steel shell immersed type and a bored tunnel. In the Netherlands, immersed tunnels are normally preferred to bored tunnels, because they require less soil cover, although it usually limits the tunnelís length. However, in the local conditions applicable to the Pannerdensch Canal Tunnel, a bored tunnel, although being deeper, could still be the same length as an immersed tunnel. The steel immersed tunnel was calculated to be the most expensive and so the plan was dropped. The concrete immersed tunnel, although cheaper than the bored tunnel, required a local construction dock and because of the major fluctuations in water levels this was a relatively expensive alternative. For these reasons, and the environmental affects, the decision was made to construct a bored tunnel.
The entire tunnel is 2580 m long, 1425 m of which is a twin tube bored tunnel. The bored part of the tunnel starts and finishes inside the flood embankments of the Pannerdensch Canal. The tunnel runs under brickworks, the canal itself, a sensitive natural area and a refilled sandpit. The approaches at each end are cut-and-cover tunnels that contain service buildings, which have vertical gates to seal off the tunnel in the event of flooding.