How do they make sure tunnels are going exactly the right way?

Question

For example, when they’re digging the Euro tunnel how do they know they’re going gmthe right way and at the right depth etc.?

In: Engineering

Answer 1

Precise measurement from fixed points of reference. In other words, if you are certain about where you’re starting (GPS) and where you want to end up (GPS) you can draw a straight line in that direction. You can carry your point of reference with you (straight down from the starting point) and the direction you need to go (compass) and the depth (multiple methods) and head out in that direction.

The measurements are checked a jillion times before starting, and throughout the dig process, especially because depth and direction will likely change over time. You then need to make adjustments to the tunneling machine to get/stay on track.

There are videos on this…digging the chunnel and through the alps.