> E.g. during the work on the Eurotunnel. Here the British tunnel boring machine was diverted into the rock near half the length of the tunnel and left there. I

> E.g. during the work on the Eurotunnel. Here the British tunnel boring machine was diverted into the rock near half the length of the tunnel and left there. It was cheaper than somehow taking it out again. AFAIK it was not just the cost, but the problem of two TBMs (British and French) meeting head to head. The british were driven out of the way so that the French ones could proceed.