Slope instability problems in the Jonica highway construction

Abstract

During the construction of the south portal of the tunnel Baldaia I along the SS106 motorway in Calabria, unexpectedly large and continuous displacements of the earth retaining structures occurred leading to a precautionary suspension of the excavation works. To study the kinematics of the observed instability phenomenon, inclinometer probes were used together with the topographic monitoring of the portal structures; it was found that the unstable mechanism was deep-seated, block-type and extending over the entire slope. In this paper the site investigation activities carried out to understand the origin of the instability process are presented. The interpretation of the observed behaviour is then given together with the description of the remedial measures suggested to safely complete the construction of the tunnel. The link between the time evolution of the instability and the sequence of the excavation works, which turned out to be an important issue in the process, is also discussed in some detail. © Springer-Verlag Berlin Heidelberg 2013.