1. Geological and geotechnical classification of soils

1.1 Preamble

It should be stressed that, when building tunnels, the primary objective is of course to ensure the stability of the structure, in both the short and long term, for both personnel and the environment. But for all projects in built-up areas, or in sensitive environments in general, the control of deformations induced by excavation is also a key factor, often determining the choice of techniques.

The range of tunnel projects and geological conditions is extremely broad, but there are at least two extremes.

• Rock tunnels

  Including at great depths, where we are dealing with a natural environment that is resistant in terms of stress levels, but cut by the discontinuities of the...