ABSTRACT
ABSTRACT: The extraordinary development of road and railway tunnels in Spain in the last 10 years has raised a number of problems related to the crossing of difficult and mixed ground, high overburdens and the increased use of mechanised excavation. A review is made concerning problems of conventional and mechanised tunnels in hard rock, as karstic ground, roof collapse, wearing of cutting tools, evaluation of support needs, overexcavation, etc. More specifically are dealt with the problems related to soft rocks, especially the theoretical and practical design of tunnels in swelling and squeezing ground as well as some cases where closure of the section and heaving of the invert occurred in soft, non-swelling rock.
