The crossing of Adda valley, one of the most beautiful landscape of region interested by the realization of the new highway “Pedemontana Lombarda”, is realized by a viaduct connected at the ends with two natural tunnels. The tunnels are designed with two twins pipes, one for each carriageway, with a cross section diameter that reaches 17 m, and will be excavated in granular soil, with variable level of cementation and a very little roofing thikness. In the paper will be presented the methodological approach adopted for geotechnical characterization of soil, the applied methods to verify the stability of excavations, and discussed the solutions adopted.