The planned intervention involves the construction of two sections of avalanche protection tunnel: one downstream of the two existing ones, and one connecting them. The slope has an incline of around 40°-45° and is particularly complex both in terms of morphological development, consisting of narrow steep ravines, and due to the presence of disarticulated rocky material which, because of freeze-thaw cycles on more than one occasion, even in the warmer seasons, affects the roadway. The tunnel structure consists of a series of reinforced concrete frames placed side by side with a spacing of 2.50 meters, made with valley pillars of increasing variable cross-section upwards, rectangular mountain pillars, and a beam that connects their tops. Given the location of the work, particular attention was dedicated to the construction site setup. The construction site was divided into four work sections to operate with limited sites at least for the most delicate phases of excavation of the foundations at the rear and the casting of the same, in addition to a section of a wall 3m high that allows for partial filling that secures the slope before proceeding to the same operations in the subsequent sections. Moreover, it is not possible to foresee complete traffic closure, except for short periods and in any case for specific time slots; for this reason, a construction site setup was planned that allows for the possibility of operating on external tracks, both downstream and upstream, in order to limit interference with traffic as much as possible and to allow for the easy movement of excavation material that must then be relocated behind the avalanche protection structure.
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