In article m,
dennis@home wrote:


"The Natural Philosopher" wrote in message
...

tunnelling by definition means that you are going deep enough to make
cut and cover impractical

So how deep is that? 20 feet? 50 feet?

Its very hard to cut and cover under main roads, railways, etc. so they
frequently put in a shallow tunnel.

There are plenty of situations on the M25 where existing roads and railways
have been put onto bridges. This would work for railways, too.

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