The underpass construction required the installation of a piling both to temporarily bear the deck and the adjacent roads, and to allow the final masonry works to be carried out. The Casing Secant Piling Technology (CSP) technique was used, since it provided excellent waterproofness characteristics, improved verticality and a higher finishing quality.
In a predominant gravelly soil, 730 piles have been installed, with diameters of 900 mm and depths ranging between 6 and 16 m. The secant piles were left in place, since they became the final masonry support of the ground adjacent to the new road.
Once the piling was ready, it was possible to carry out the excavation of the ground between the two rows of piles until reaching the underpass ground level. The precast support beams in pre-stressed concrete supporting the deck of the viaduct were placed on the side abutments of the underpass and on the provisional central piles. The procedure ended with in-situ concrete casting.