Construction of a 60m long approach cutting and a tunnel and passage with a length of 210m in loose material composed mainly of gravel and silt. Retention of the cutting by secant piles of 26-31m and prestressed anchors. Average section 29 m2 for the passage and 120 m2 for the tunnel. Mechanical excavation of the cap under the protection of preconsolidating jetting columns followed by excavation of the bench. Reticular framing and shotcrete with steel fibres as a means of support after the excavation.