Subject: Crossrail TBMs
From: Martin Young MSc (Eng) CMILT IEng MIET

I read with interest the article on the new TBMs for the Crossrail Project. Having worked on a number of heavy rail and metro projects, I have an interest in tunnelling and the associated costs.

There were no costs mentioned in the article, which would have been interesting to compare in respect of the projected construction costs of High Speed 2, of which I am in favour.

With all the environmental controversy raging over HS2's path through the beautiful Chiltern Hills and the Misbourne Valley, I reason that a twin-bore tunnelling option has to be viable.  The construction figures for HS2 state that tunnelling costs have been estimated on the 'high side', and recently published information has revealed that a short tunnel section had been proposed for the Wendover section.

There has also been a technical statement which argues that the trains would have to go considerably slower through tunnels due to the roughness of the tunnel wall surfaces creating aerodynamic drag, and mitigation measures such as pressure relief vent shafts regularly placed in the countryside would be unsightly!

I suggest therefore, to the 'powers that be' that once these TBMs have been used on the Crossrail Project, that they be mothballed along with the segment manufacturing plant to be ready for boring environmentally friendly tunnels under the Chilterns once the re-design has been approved. 

After all, the TBMs will be of a similar diameter for the use of main-line rolling stock powered from the overhead catenary. The tunnels could be designed to have suitable gradients to allow the trains to use their regeneration equipment effectively, the many tunnel wall fixings, which create a large part of the aerodynamic drag, be reduced to the absolute minimum.

In these times of austerity, and the ‘nimby’ culture, my suggestion must win hands down on both cost and environmental savings, and I'm sure that the resident of a large country estate on the hills near to Ellesborough and Wendover would be only too proud to show off the new High Speed 2 railway to his many foreign visitors.