Knowing the precise geological conditions is of key importance to the people planning a tunnel construction. Where can you find fine-grained, soft and plastic rock, such a clay-like soil? Where does the subsoil turn into sandy gravel? At what depths and in which stone layers can groundwater be expected, and how can this be managed during construction work?
And finally, where could there be areas of significant artificial backfill, such as in a former glacis? These issues determine the route of the tracks taken, construction methods used and safety measures required. Illustrating the geological conditions on maps and using models is a key part of planning the construction of an underground line.