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Finite elements analysis of an underground collector installed by pipejacking methodUsing the commercial software RS 2 , a 2D finite element program for soil and rock application, the ground response to pipe jacking in pipeline installation in Avilés (north coast of Spain) was analyzed. The geology of the location comprises Quaternary deposits on both flanks of the Avilés estuary and includes different highly variable geotechnical behavior. Both axi-symmetric and plane strain analyses were carried out in RS 2 to simulate in 3D the ground response to pipe advancement. The results demonstrate that the vertical displacements at specific positions in the immediate vicinity of the pipeline were small. The maximum deformation at ground surface was shown to be less than 1.5 mm, which was still safe. However the displacements were found to vary depending on the local properties of the materials drilled. Stress distributions were also computed.

The presence of large palaeo-landslides can hinder the construction of railway lines if they cause an alteration of the natural balance of the slope, significantly increasing the cost of the project. During the construction works in a section of the Madrid–Asturias high-speed railway line (Spain), a large-scale hillside instability affected 460 m of the section. The ground movement began 10 months after the start of the excavations and remained active throughout the observation period (2008–2010). Data provided by fieldwork, boreholes and instrumental monitoring have allowed the investigation of the geological units involved, together with the geometry and the kinematics of the mass movement. This landslide involves a Paleozoic basement with an estimated volume of 4 400 000 m 3 . It shows low displacement rates (<45 mm a −1 ) and was accommodated on a single surface of rupture, which reaches more than 60 m depth. The kinematics is favoured by structural and lithological conditions, there being a strong rheological contrast in the lower part of the mobilized ground. This movement is linked to a large palaeo-landslide that was partially reactivated when excavations undermined the lower slopes of the hillside. Technical solutions for the stabilization have already caused an additional cost of 17% over the initial budget.