For example, lining, invert, bias and so on words,, to answer the full thank you
Bias: refers to the formation of the tunnel, resulting in uneven pressure. To provide you with a few books you go to see the explanation. The site is easy to understand.
Inverted arch: the general shape of the tunnel are horseshoe. Then the bow that you look up at is called an arch or vault
You haven't even touched the tunnel. Simply to say that the lining is the use of concrete or reinforced concrete tunnel inside the template pouring. The author is to stabilize the stability of the rock itself, followed by the tunnel in order to facilitate the application of.
