A RELIABLE CONVEYOR
MAINTENANCE SPECIALIST
MAINTENANCE SPECIALIST
The Severn Tunnel has been closed for a major repair project, which will be made particularly challenging by the hostile damp and salty environment that will make the repair and maintenance of conveyor belts an ongoing task.
Connecting south-west England with south Wales, the 4.35-mile tunnel enables trains to serve cities like Bristol on the English side and Newport and Cardiff on the Welsh side.
The work, which is now underway, will continue until June 8th and will involve the replacement of overhead power lines and the renewal of tracks, with the benefits felt beyond the tunnel as it facilitates the reopening of the old Henbury line in Bristol, with a new station at Brabazon.
Work on building the tunnel began in 1873, but it was not until 1886 that passenger railway services between Cardiff and Bristol commenced. The slow pace of progress was due to the difficult environment and problems that engineers and construction workers had to tackle.
During the 13-year project, there were multiple technical problems, highlighting challenges that still exist in some forms today:
· There were floods from the sea
· Water ingress came from many points
· An underground saltwater stream was breached more than once
Even today, the high level of saltwater in the atmosphere and on the tunnel floor has a significant impact.
In a statement on the project, Network Rail described the tunnel as “one of the toughest environments on the UK rail network, where moisture and saltwater accelerate wear on equipment.”
It added: “Since electrification, the overhead power system has been prone to corrosion and electrical wear, leading to more frequent maintenance.”
This is the reason for the work, which will involve the installation of more corrosion-resistant copper wiring to maintain the electrical connection.
As well as the wire and track work, the project involves:
· Replacing the 838 bridge arms that hold the wires in place under the roof
· Improved drainage works
· Surface works to restore the Henbury line
The inhospitable working environment also highlights the likely need for ongoing conveyor belt repair and maintenance, as this equipment will also be affected by this corrosive and unforgiving environment.
Indeed, one of the reasons that conveyor belt maintenance is so important is not just the wear and tear that can be involved in tunnel work, especially if that involves the excavation of earth and rock during the construction phase, but the tunnel conditions themselves.
Like any tunnel that passes under a sea or a river, the tunnel will always have some water ingress to deal with, not least because its location means that water will find its way in from outside even when it does not leak from underground watercourses and rocks within.
Pumps can help to control this, but this cannot eliminate water from the vicinity, especially when the air in the tunnel is wet and humid.
Moreover, because the tunnel runs so far underwater, it cannot benefit from ventilation shafts in the manner of tunnels passing under features on land, such as hills or city streets.
This means the kind of salty environment found in the Severn Tunnel can exist in many tunnels that pass under the sea or estuaries, although this can vary depending on the age of the structure.
For example, the proposed £402 million project to link different islands in the Shetlands by road, which would copy a similar scheme in the Faroe Islands, will use modern concrete and also use the most up-to-date knowledge to deal with issues like ion corrosion.
This is a problem peculiar to undersea tunnels and studies have shown it is best resisted by having very high-quality concrete in place and swift and regular maintenance.
However, tunnels like those that could be built in the Shetlands, the ones already in place in the Faroes, and the Channel Tunnel are all instances of modern construction methods, using different excavation methods and materials from Victorian structures like the Severn Tunnel.
Methods of construction like the shield tunnel system and the use of concrete are more effective in providing a waterproof barrier than exposed rock or lining with bricks.
The oldest tunnel built underwater in Britain is Brunel’s Thames Tunnel in east London, which was built between 1825 and 1843 and, like the Severn tunnel decades later, the construction project suffered many delays due to flooding.
Originally a foot tunnel, it switched to rail in 1865, later became part of the London Underground network (East London line) and is now part of the London Overground.
Although not faced with the scale or salinity of the Severn Tunnel, the maintenance involved in such a tunnel will often have been much more challenging than in those tunnels built more recently using more modern technology.