Do you have a special word for ...?

Knock off time

Thats a joke fansy.
I dont think there is a single word to describe what you are asking.

new unity

You can only express the emotion felt which is how it is reported generally. At Last! Hurray! Done! Fait Accomplait! Gosh! Whew! Ahhh, I can rest now... and so on.

Pink Slip Time, you mean.

Sorry fansy, more joking around. I also don't believe there is a word for the situation, probably because their aren't enough tunnels being completed to merit a descriptive word. When tall buildings are completed, it is called "topping out", but that is a relatively common occurance.

If you want to make a historical reference, you could call it the "last spike".

It's called a "breakthrough."

Yeah, the tunnel has been broken through finally ... This should be the technical term I want.