To make the biggest Italian river navigable all year long; to increase its navigability by 37 km; to approach Italy to the standards of the most advanced European Countries: this is the goal of the new navigation basin of Isola Serafini, one of the most important waterway works in Italy.
As well-known, a navigation basin is a hydraulic construction that allows making channels and rivers viable at different levels. The central part of the basin is formed by a tank delimited by two side walls and by two watertight doors. When a boat enters the basin, doors close and the water is made to ascend or to descend through aqueducts to bring the vessel in line with the body of water it faces. A work where is successfully present the British company Groundforce – operating for 30 years in the hydraulic propping sector.
Project and cost of the work
The navigation basin of Isola Serafini is part of the programmes of navigation enhancement on the River Po planned by AIPO, the Inter-regional Agency for the River Po, and will replace the current one (dating back to the 1960s) and no longer usable for most of the year due to the reduced water levels of the river.
The construction cost is around 40 million Euros. The basin, which required ten years of study before the definitive design, is conceived to accommodate vessels of up to 110 m in length and 11.50 m wide, with a net displacement of up to 2,000 tons.
The big navigation basin will be 115 metres in length and 12.50 metre wide, with a minimum water depth exceeding 3 metres, even in low water conditions. A massive work, whose construction needed a forefront engineering technology.
The Isola Serafini design requires in fact an 18m-deep excavation approximately, supported by a concrete diaphragm wall constructed to a depth of 35 metres.
The advantages of the hydraulic telescopic propping
Due to the considerable excavation depth, it was necessary the construction of suitable contrast elements for reducing the diaphragm deformation in excavation phase, therefore they decided to use hydraulic telescopic propping systems by Groundforce. An alternative solution to the standard steel structural works and to the construction of braces that has offered several advantages from the point of view of the implementation, costs and execution times.
The architect Jacopo Zabeo of Groundforce tells: «In Isola Serafini yard, the challenge was to provide a propping system spanning about 28 metres, which was able to support very high loads with high thermal variations. The aim was instead to provide the contractor with a flexible system allowing our props to be moved rapidly as the work on site progressed, this means they could complete all the work with a limited number of props. I would like to underline that in this case, to cover all 110 metres of excavation, only 16 props were used in all, installed on two levels and spaced at about 5.50 metres».
As Giordano Ciarlo, technical supervisor of the yard explains: «In the study phase, the four rows of braces were replaced by Groundforce props, as suggested by the work management. Applying braces in a sandy soil in presence of groundwater would have been difficult, as we have seen in other large hydraulic projects in other Italian regions. The traditional system of propping with metal framing might have caused problems during the removal because of expansion, with the additional potential risk of accidents».
Mr Ciarlo adds: «The advantages of Groundforce’s technology are remarkable as the hydraulic props can be adjusted with a monitoring limit value up to 900 tons (although in this site we set a lower limit of 650 tonnes) and with control devices permitting to monitor the load continuously».
The remote load monitoring system
In this yard, in fact, for the first time in Italy, they used the remote load monitoring system. On 4 of the 16 props rented for the basin construction, they installed load monitoring cells that constantly check the reactions inside props. If some anomalies should occur as to the efforts foreseen by the project, the system will immediately send an alarm to the portable phones and to the emails indicated by the customer.
The used props
They are MP500, with maximum loading capacity of 5000 kN (SLE). Their length almost reaches 28 metres (and the maximum distance reached by those elements, without needing intermediate support works, is even 50 metres) and they are composed by a hydraulic unit with 500 mm-extrusion connected with modular extensions with 1220 mm diameter. Currently, there are 16 props of this kind installed since February 2015. The propping system is used on two levels since we are dealing with an 18m-deep excavation approximately.
GF solution was chosen also thanks to the remarkable reduction of work times. Being a work “in progress”, the possibility of displacing a 27-metre prop in few hours notably shares in the implementation speed of the construction.
According to the architect Zabeo: «For this intervention, Groundforce technical assistance in the yard simply executed an in-depth training and information of the customer’s technical team about the use and maintenance of our equipment, afterwards the customer itself, for the entire duration of the yard, managed autonomously the installation, the removal and the handling of our props. The only operation we continued to oversee personally was the displacement of the wireless receivers of the signals coming from the load monitoring systems installed on the props. Operation made necessary by the fact that the work extended for a length of about 110 m (the Groundforce receiver, in fact, has an operational range of around 60 metres). Due to the delicacy and the importance of that intervention we then preferred it was carried out by our specialized technicians».
Groundforce props will be maintained to support the excavation until the accomplishment of the concrete structures and the lock gates are in place. Afterwards, we will just have to navigate effectively.
Groundforce is a division of Vp plc, Group with headquarters at Harrogate, in the United Kingdom. Groundforce supplies complete solutions for the construction sector, i.e. Propping systems, Shoring equipment, Piling, Pipe Stoppers, Pressurized sealing tests with compressed air and pump sale and renting. Groundforce products have been used in some of the main projects in the United Kingdom, including the rail link under the English Channel, the tunnel under the river Tyne, the terminal 5 of Heathrow airport, Wembley Stadium and the Olympic Games in 2012.