Building a tunnel is an in-depth process requiring construction company owners and general contractors to assess several aspects of the project and its surroundings. For instance, you’ll need to evaluate the type of ground that the tunnel is being built on (soft ground, hard rock,  soft rock, subaqueous) before construction begins.
That being said, the procedures involved in constructing a tunnel are relatively consistent. These processes include the following:
Investigation
Excavation
Material transportation
Ground support
Environmental control