Rehabilitation of Serra del Corvo Dam

The Serra del Corvo dam is located into the catchment area of the Bradano River and intercepts the Basentello stream at an altitude of 243 m above sea level. It is in the municipalities of Gravina di Puglia (BA) and Genzano di Lucania (PZ).

It was built between 1969 and 1974. It is in loose materials with internal clay core. The height is 41.50 m, and it generates a reservoir with a maximum capacity of 42.65 Mm3.

The project consists of the seismic inspections of the dam and ancillary works, geotechnical study, geognostic investigations on reinforced concrete structures and related laboratory tests.

The analyses consist in the seismic evaluation of the dam and ancillary works in the light of the technical standards for dams (NTD 2014) and the technical standards for construction (NTC 2018). 

The core of the dam is made of compacted clay silts of low permeability and crosses the permeable surface formation up to the basement also made of clay. The counter cores are made of coarse-grained materials of high permeability. Between the core and the upstream and downstream flanks there is 1 meter transition zone reaches the nail of the facing.

On the upstream facing there is a coating in spliced concrete slabs of the thickness of 30 cm, arranged on a sand and gravel substrate of the same thickness of 30 cm. The abovementioned coating in some areas is unstable. 

Main ancillary works are the following:

• Surface spillway n°1:  the surface discharge is a free threshold in concrete, with a threshold of 71.00 m, shaped in a U-shape and includes a large tank, also in concrete. It is followed by a connecting chute that leads into tunnel No. 1 of the semicircular vault type. The spillway is equipped with irrigating external buttresses.
• Surface spillway n° 2 and manoeuvring shaft: the work covers the surface discharge and the access shaft to the manoeuvring chamber. The surface spillway consists of 4 spillways, 2 on each side, manned by as many fan gates with automatic operation. The spillways, each 10 m long, are placed on the sides of two converging axis gutter channels, with an angle at the centre of 60°, to make room, in the middle, for the access shaft to the manoeuvring chamber of the sluice gates of the bottom drain. In the middle of the two gutter channels is located the access tower to the manoeuvring chamber of the bottom discharge gates. The tower, triangular in plan, allows you to reach through several flights of stairs the base of the manoeuvring shaft, at an- altitude of 49.85 m above sea level.
• Dissipation tanks: the discharge tunnels 1 and 2 flow into two dissipation tanks located downstream of the body. In one to the right, it merges the tunnel n° 1 and has a length of 228.56 m, in the other, further to the left, flows the tunnel n° 2 and has a length of 205.36 m. Laterally the tanks are delimited by gravity walls of variable height: for the first 30 m the walls have a height of 7.50 m from the extrados of the base slab; after a stretch of length 30 m at height. Variable the height of the wall is brought to 4.00 m until the end of the pool. The two tanks are separated from each other by a central gravity wall. The bottom of the tank is made up of reinforced concrete slabs of different sizes and with a constant thickness of 50 cm joined together.

The services provided are the following: the reassessment of seismic safety, the geotechnical study of the dam with the consequent definition of the interventions to improve the structural conditions from the seismic verification and from other related investigations.

The proposed seismic upgrading interventions mainly concern the reinforced concrete works and include for the various works the execution of tie-rods, piles, hooping, reinstatement of concrete cover.