On Tue, 08 Sep 2009 18:18:43 +0100, Arthur Figgis
wrote:

wrote:

I thought Crossrail was being built? Because they have already started work,
are you saying this work could be stopped?

That is what happened to the Channel Tunnel in 1970-something.


That isn't quite the same as what happened to the Channel Tunnel in, I
think, 1974. The Channel Tunnel wasn't cancelled, it just never got
the go-ahead to start.

There was a feasibility study and associated demonstration project
under way when Harold Wilson's Labour government came into power in
1974. It was hoped that, based on the success of the demonstration
project, the construction of the Channel Tunnel would be authorised as
a joint British/French publicly financed project.

The feasibility study showed that a tunnel could have been built
through the chalk marl. The demonstration project was a success and
showed that a tunnelling machine could excavate and line a short
section of the small diameter service tunnel in competent chalk marl.
But that's all it showed.

When Labour came to office, the country was on a three day week with
rotating power cuts for all but essential services. The government's
tax take had fallen dramatically because industrial production had
been badly disrupted due to the coal miners' strike, reducing
corporation tax receipts, and because working hours were much
reduced, reducing income tax. In short, there wasn't any money, and a
grandiose project like the Channel Tunnel was never going to be given
the go-ahead at a time like that.

So the demonstration project was completed and the feasibility study
was written up. The tunnel workings were then sealed. Then nothing
happened, literally.

Nothing was "cancelled", because there was nothing to cancel.

With the benefit of hindsight, we can now say that it was probably a
good thing that the project didn't get the go-ahead at that time. The
ground investigation had been rather perfunctory and some major
geological problems were missed.

Subsequently, in the 1980s, a more detailed ground investigation was
carried out. This also failed to identify geological problems on the
English side which caused serious problems when the project was under
way. The detailed ground investigation successfully identified some
even more severe problems on the French side. As a result, the French
tunnelling contractors invested a lot of money in very sophisticated
machines which offered full support of the excavated face with a
bentonite slurry.

This was a slower and more costly method of tunnelling but the French
tunnellers coped with everything the ground conditions threw at them
and more or less stayed on programme. Indeed, they went so well
compared to our tunnellers that they continued far beyond the original
agreed point and into English territory.

On the English side, a more optimistic view was taken and face support
was not included. In the event, the ground conditions were not as bad
as on the French side, but bad enough that the lack of face support
and huge ingress of water caused severe delays to the tunnelling.

Had the Channel Tunnel been given the go-ahead in 1974, the optimistic
view would have prevailed on both sides because of the inadequate site
investigation, and the sophisticated machines used by the French were
not available at that time. So there would have been major problems -
even worse than in the Tunnel that was built - and the whole cost
would have been borne by taxpayers, which would have been a disaster.
It is quite possible that the project would have had to have been
abandoned until better technology became available.

In the event, the problems were mainly confined to the English side,
and the whole of the massive cost overrun was borne by investors in
Eurotunnel and the lending banks, sparing the taxpayer almost all of
the pain.

As taxpayers, I think we should be relieved that this burden did not
fall on us. With the severely damaged economy that was left to Labour
by the grossly incompetent Heath/Barber Tory government of 1970-74,
the public finances could not have sustained such a big hit.

With Crossrail, two of the three major tunnelling contracts have just
gone out to tender. So, unlike the Channel Tunnel in 1974, there *is*
a Crossrail project in place. I believe the Crossrail team are aiming
to have the tunnelling contracts let and started on site before the
general Election, in the hope that it would make the project very
difficult to cancel. We will see, ;-)