Selection of excavation method depends on ______

Pick the rock considered as soft rocks for tunnelling.

When can the rocks act as a natural arch?

Which type of geological structure can be rectified by grouting?

Geologically, how many classes of tunnels are recognized?

Lithology does not affect which parameter?

Layers dipping at angles up to 45° may be called ______

Which outline is preferred for weak rocks with unequal lateral pressure?