The work and the technique: Val di Lei Dam, Italy

The Val di Lei Dam is a masterpiece built by the construction company, Gi.Lo.Va.L. - to which Girola and Lodigiani belonged (both companies later merged into the Webuild Group). It was among the double curvature arch gravity dams with the largest crest length in the world at the time. 

A 1:66-scale wooden model was made during the design phase, and lab tests were carried out at Ismes, in Bergamo, to reproduce the stresses that would impact the dam: self-weight tests and hydrostatic thrust tests were carried out to understand which lines underwent maximum stress. The level of safety was determined by increasing by 5 times the normal load.

Construction works in the Valle di Lei (Di Lei Valley) began during summer 1957. The dam was reachable only during the summer season, from the Italian side, by foot. So, two cableways were built: one to transport people, the other to move materials. The passenger cableway, which almost always moved in parallel to the other, covered, in only two sections, a distance of 14km, which at the time was a real record. It connected the base camp to the Campodolcino site. 

In 1958, a tunnel suitable for vehicles was built that brought to the construction site from Switzerland, widening the Avers road. An actual small village capable of hosting 1,500 workers from the site was also built. 

Works began with the excavation works to find the rock strata appropriate to weld with the cement. The 55 concrete segments (vertical sections) of which the dam is made were built: a real wall of blocks positioned next to the other. Inside, are horizontal small tunnels connected to very high vertical shafts were created.

The cement plant involved in the work had to be equipped with a new department to meet the exceptional need for more than 2,200,000 quintals of cement to build the dam. Materials were transported by rail to Chiavenna. Then, with a truck, to the cableways stations. Every day, 12,000 quintals were taken from the valley floor to the concrete plant.

During winter, it was impossible to work outdoors due to the temperature that could even reach -20°C; only during the last years of construction, it was possible to work inside the dam and the labs, to carry out the continuous concrete measurements: freezing, permeability and breaking tests. During the construction period, 650 samplings and nearly 10,000 tests were performed.