The port of Piombino is situated in Livorno, Tuscany, part of central Italy. Since 2012, the port is moving ahead with the realisation of the works foreseen in the Port Master Plan, a largescale project for industrial, logistic and port development. Until 2020, the area will be the object of sizeable infrastructural investment to give the port new quays, accessible from the sea with depths of up to 20 metres, and from the land side with direct and suitable road and rail connections. Thereafter, up to three and a half kilometres of quaysides and around 800,000 square metres of port space will be available, in addition to those currently existing.
The Port Master Plan includes the construction of a new dock with a 350m long and 50m wide East Quay. The dock will be dredged to 20m below the average sea level (l.m.m.).
The original tender for the quay wall specified a combined wall with 38 m long tubular piles Ø2060mm of variable wall thickness (26 and 32 mm) in the function of the depth, and 29 m long intermediate sheet piles with an elastic section modulus of 3,870 cm³. Both tubes and sheet piles had a steel grade S420N.
The wall thickness of the tubular piles was variable according to the following scheme:
- from +1.00m to -6.50m l.m.m. : 26mm;
- from -6.50m to -24.00m l.m.m. : 32mm;
- from -24.00m to -37.00m l.m.m. : 26mm.
The combined wall is anchored with steel tie rods Ø120mm at intervals of 3.53m to a reinforced concrete beam, positioned in the vicinity of the breakwater at the sea-side of the quay platform. The distance between the tubes and the anchor beam is about 38m.
In order to provide a more economical solution and a faster delivery, ArcelorMittal, in collaboration with CMC, proposed an alternative design using spirally welded tubes with a constant wall thickness of 26mm, reinforced with two internal steel plates of 26mm thickness.
The internal reinforcement plates consist of several calendered steel plates (600x26mm) welded both longitudinally and horizontally to the tube. They are placed in the positions with the highest stresses: horizontally at 90° from the clutches and vertically from -4.50m to -25.00m l.m.m.
A marine coating system was applied down to a level of -6 m to the exposed face of the tubes and sheet piles for corrosion protection in low water and upper immersed zone.
A part of ArcelorMittal's service to the client was the delivery of a complete custom-made driving frame for deep-water installation, which enabled the accurate driving of the 111 tubular piles.
The driving template has 5 tube positions; it is vertically attached by chains on one side to an already installed tube and on the other side to a temporary support tube. In each sequence, four tubes can be installed before shifting the template to the next position. Plastic rolls keep the tube in the exact position and avoid potential damage to the coating. There are special guides for the interlock in order to prevent rotation during the installation process.
Installation of the wall was done from a barge, using a free hanging ICE1412C vibratory hammer (max. centrifugal force 2300kN). The initial seabed level was at -10 m to -12 m. Down to a level of about -32m, a medium dense sand layer was encountered. For the final meters down to pile toe level of -37 m, a stiff clay layer had to be passed. The pile driving works started in June 2014 and were completed in 4 months time.
Total = 6,823 tonnes
Main contractor: JV CMC / Sales SpA