Manchester’s plans to extend its transport network by going underground may bring some technical challenges, which the use of reinforced concrete could help to resolve.
Plans to build three new tunnels, one for trains, one for trams and one for a new Tube-style underground rail system, were unveiled several months ago when Andy Burnham was Greater Manchester Mayor and have just been endorsed by his replacement Bev Craig.
There may be much debate about the cost, but for engineers whose job is to construct the system, a key issue will be how to tackle the geology and any underground hazards they meet. In some cases, reinforced concrete formwork may help to shore tunnels up.
Manchester’s bedrock is mainly sandstone, which is sufficiently firm for tunnels to be dug through it.
Indeed, various plans for a tunnelled underground have been proposed in the past, the last one, the Picc-Vic line of the 1970s, actually having some tunnels partly dug before the project was cancelled.
What Underground Obstacles Exist In Manchester?
Where any tunnelling will have a possible challenge is where it may either meet or run close to existing tunnels or underground passages. These include:
- Culverted rivers such as the Irk and Medlock
- A tunnel linking the River Irwell with the Rochdale Canal
- The remnants of the Guardian Exchange, a Cold War bunker whose passages are now used for broadband and telephone cables
These potential obstacles exist in the city centre, but often the solution is simply to ensure that when tunnels are close, there is a solid barrier between them.
Under London, which has a plethora of tunnels including the Tube, new tunnels sometimes have to be measured with great precision and reinforced to prevent encroachments on each other.
In some cities, such as Newcastle and Glasgow, the presence of coal mines has posed further tunnelling challenges. However, in Manchester, the planned tunnels are not near any mines.
However, that could change in the future, should an extension head east towards the Bradford district, close to several sporting and entertainment venues today, but once home to several mines.
