To those who believed Geological hazard and the lack of appropriate survey, design and construction inst- ments for tackling those terrains we call diffcult, with good prospects of success, have always made the design and construction of underground works a risky affair, which could not therefore be faced with the same degree of accuracy as other civil engineering works. As a consequence they have always occupied a subordinate position with respect to similar surface constructions and in the past they were only resorted to when the latter seemed impractical or of little use. However, decisive...