Work on Brazil’s Prosub advances

With the utilization of special construction equipment, the first phase of works in the program which will enable the construction the first Brazilian-built nuclear submarine has already been concluded. Project will be the theme of one of the exhibit halls at Construction Expo.

The Brazilian Navy’s “Programa de Desenvolvimento de Submarinos” (PROSUB -  Submarine Development Program) has just completed its first step: the construction of the “Unidade de Fabricação de Estruturas Metálicas” (UFEM – Steel/Metallic Structure Manufacturing Unit). This is one of the main units of the shipyard and naval base project (or EBN for “Estaleiro e Base Naval”), which represents about 30% of the planned works.

Before moving on to detailing these works where 542 pieces of heavy equipment are in action, including self-owned and rental equipment (see further below), it is worthwhile to take a moment to explain the project: PROSUB was conceived as of the establishment of an agreement for transferring of technology between France and Brazil in 2008 with the goal of designing and building conventional diesel/electric-powered submarines and vessels driven by nuclear propulsion. With that Brazil becomes the sixth country in the world to possess this technology, following the USA, China, France, England and Russia.

COMPLEX

The company chosen for the project was DCNS which partnered with Odebrecht to form the Consortium ‘Itaguaí Construções Navais’ the consortium responsible for the construction of the EBN Complex, as well as for designing of the first five submarines (one nuclear and four conventionally powered). “This scope of works involves several steps, the first being the construction of the UFEM,” says Fábio Gandolfo, managing director for the shipyard and nuclear areas at Odebrecht Infrastructure.

According to him, the UFEM is an industrial complex consisting of 45 buildings with a constructed area of 57,000 m². In this structure, there is a main building that houses the central machine shop and other 12 buildings where the sections of the submarines will be assembled. “The sections are made of special steel plates which come from France and are folded at NUCLEP (Nuclebrás Equipamentos Pesados S.A) located beside the UFEM,” says Gandolfo.

NUCLEP is a traditional supplier of heavy machinery for metal structures. Today the company belongs to the Brazilian government. The company owns large equipment such as presses and ‘calenders’ (roller presses) which are capable of shaping the steel plates to form the metal rings that will form the sections of the submarines.

CHANGE OF SOIL

>Once molded, the plates as sent along to the UFEM whose construction works were completed in March of this year and involved about 130 pieces of equipment and trucks in the process of earthmoving and grading. “It was necessary to change the soil since the region was flooded in certain places,” reports Ricardo Cunha, equipment manager at Odebrecht for the EBN complex.

The removal of the soft soil involved the work of 45-ton excavators – which are more productive for this type of task than excavators in the range of 21 tons or even intermediate-sized 35 t equipment. These excavators were teamed up with 25 dump trucks equipped with Rossetti 16 m³ trailer boxes lined with a special coating for soil and rock. “After the soft soil was removed, a landfill containing a mixture of gravel and soil was performed using the same equipment,” describes Cunha. Once the landfill material was deposited, the site underwent compaction using 12-ton roller compactors for soil.

BUILDINGS

Due to these dimensions, the central pillars have been produced in situ using climbing formwork for concreting. The concrete used in all the construction work is produced by a 60 m³ mixer plant. The pillars with smaller diameter and height on the other hand were either precast at the site itself or provided by a company in the neighboring city of Seropédica. “To raise the precast pillars, we used telescopic and lattice boom cranes with capacit8es ranging from 25 tons to 200 tons,” explains Cunha, noting that larger cranes, in the range of 500 t, were also applied in the handling of UFEM presses during the phase of industrial assembly.

In these buildings, the metallic roofing and steel structures were also assembled and hoisted by cranes. “The steel modules came from the state of Santa Catarina, directly from supplier’s factory,” says Ramos. “They were assembled and adjusted by the supplier himself, but always under our supervision, with the rigging plan.”

INSTALLATIONS

Involving pipelines and networks in general, the UFEM’s internal installations also represent a point in which the project is distinctive. Alongside the building, a central utilities facility was built with a power substation, generator, compressor, small sewage treatment plant, demineralized water and other resources. From there, the inputs required for the operation of the UFEM will be distributed via ‘pipe racks’ (i.e. suspended pipelines). According to Ramos, this mechanism is divided into three structures: a catwalk for support, the pipe racks themselves and cable racks. “The assembly thereof also required the use of special equipment,” adds the director.

In addition to the cranes, which are also used to hoist the modules that were already assembled, the team used 45 aerial platforms for welding and installation of the suspended pipes. Personnel lifts, according to Cunha, were also applied in performing civil engineering services, such as assembly and installation of the power grid. “These are articulated (knuckle boom) platforms with heights that vary to suit every construction need,” he says.

NORTH AREA

After the UFEM, the next part of the work is the North area of the naval base. In the plan of logistics, the sections to be assembled will be transported from the UFEM to the base over a distance of 3.5 km. Presently, there is an on-site precast element and tubular pile plant which supplies the South area where the shipyard and naval base are under construction. When PROSUB is fully operational, however, the North area will serve to control access to the naval base since it is situated on the only access by land to the region. “Precisely as a result of this, it was necessary to build a tunnel between the North and South areas which, in itself, constituted yet another major work in this project,” Ramos assesses.

TUNNEL

The tunnel in question is 703 meters long, with a width of 14.5 m. “This project firstly involved the establishment the entrance portal on one of the sides, which required crossing a vegetation layer with 36 meters in depth until we reached the bedrock,” says Ramos. Once at the rock, began the process of drilling the blast hole grid in which we applied two Sandvik drill jumbos, with two and three booms. “After this operation, we used telehandlers to manually position the sticks of dynamite,” adds Cunha.

Following detonation, the 45 t excavators returned to the scene to remove the blasted material, supported by 10 dump trucks equipped with specially lined 16 m³ trailer boxes to handle rock. Since the tunnel will only be used by PROSUB, there was no need to finish the walls which were simply evened out by removal of loose surface material using hydraulic breakers (a process referred to locally as “bate-choco”). “”We also applied shotcrete for safety using special robots manufactured by Putzmeister,” he says.

Ramos explains that the tunnel was built in two stages, starting with the establishment of the crown (‘roof) and then working down. This was necessary due to the width of 14.5 meters which did not allow the excavation of the section all at once, and prevented the use of drilling jumbos that do not reach that distance. “The shafts of jumbos can reach as far as 8 meters away, at most,” he explains.

SOUTH AREA

Parallel to the construction of the tunnel, the Odebrecht team worked on the South area; the maritime part of the works. In this case, the first action taken was the removal of contaminated soil and water – an encumbrance left in the region by industries that were established there in the 1970s. “For this, we used suction dredges and pump, removing 300,000 m² ? of contaminated material that was placed in ‘geobags’ – large bags that are specifically designed for storage of this type of material,” says Sérgio Pinheiro, director of the contract for marine works. The director points out that this dredging technology was chosen to enable work in shallow areas; something necessary in this case since the depth was less than three meters in some sections.

The geobags with stored material occupy a restricted sector on the grounds of the shipyard, which also received another 9 million cubic meters of landfill earth, based in marine reserve that was previously authorized by environmental protection agencies. The process, according to Pinheiro, represented another differentiated action of engineering, which came to involve the combined work of six dredges. “In that case, we used suction and pumping equipment for shallow areas and ‘hopper’ dredges, which afford greater productivity in areas of deeper water,” says Cunha, reminding us that tractors, motor graders and excavators worked in the topographic correction of the hydraulic landfill. The hopper dredges, in turn, used one-meter diameter pipe through which the material was pumped until it was released in landfill that was under construction.

ROCK FILLING

Parallel to landfilling, engineers drove tubular foundation piles for the pier and adjacent structures. In this case, the piles produced in the North area were loaded onto barges that transported them to the location at which they would be driven where cranes fitted with hydraulic hammers also operate. “We have as many as six barges equipped with cranes of 160 tons or 250 tons, simultaneously,” says the equipment specialist at Odebrecht.

Another operation of maritime work that involved the use of barges was the construction of a ‘careful rockfill’.  In this case, to hoist and position each stone of the rockfill, one by one, we used two 35 ton excavators equipped with an elongated boom (15.5 m) manufactured in England especially for this demand, which were placed on a barge positioned beside the pier. The structure includes a landfill, which will serve as a quay for the dock. “In the rockfill, the ‘careful method’ is needed to prevent rocks from colliding with piles that have already been driven into place,” Cunha explains. According to him, besides the excavators, cranes equipped with a hook block and ball also acted in performing the task placing the larger stones.

When the hydraulic backfill was completed, work also began on the construction of the dry dock, where the submarines will be assembled, tested and unloaded. During the preparation of this report, that part of the work was at the stage of construction of the diaphragm walls and of excavation for the foundation in which is a special machine called a ‘hydromill’ is applied.

According to Cunha, this machine works with the application of bentonite slurry which is used to support the landfill. It then activates a diamond coated disc of about one meter in diameter which makes a cut along the entire length of the diaphragm wall. The next step is the placement of the metal armature and concreting. This is done along the entire length of the wall that will form the dry dock. “Following that, all that needs to be done is to remove the landfill from the middle of the dry-dock dike and format the floodgates," Cunha sums up.

Schedule foresees production for as early as 2014

PROSUB is expected to start manufacturing submarines as early as next year with the beginning of the assembly of the first conventional unit (diesel / electric powered). The submarine should be ready in 2015, going into final operation two years later after the necessary tests. The nuclear-powered submarine along with the other three conventional submarines are expected to go into operation by 2023.

A mega-fleet of equipment

At the end of its first phase, the PROSUB construction project mobilized a fleet of 542 units of equipment of dozens of types and models, including excavators, backhoes, trucks, trailers, support equipment, pavers, cranes, gantry cranes, concrete mixer trucks, compactors, boats, barges, motor graders, etc. With 64 units, among self-owned and rentals, dump trucks made up the largest number of large machines at the work site, second only to generator sets (with a total of 98 units).

Thematic Exhibit Hall will present project at Construction Expo

Those who visit Construction Expo 2013 can get to know all the details of the PROSUB project. The exhibit hall devoted to PROSUB will have several interactive attractions, including an area on sustainability, a mock model of a submarine sail and conning tower, photographic panels with aerial views of the construction works, a VIP lounge, 3D cinema and other attractions. “Our proposition for the event is that the exhibit should be totally interactive, allowing visitors to get to know the project as if he or she were in it, via interactive display screens, photo enlargements of the phases of the works, 3D and other resources,” concludes Fábio Gandolfo, superintendent and managing director for shipyards at Odebrecht Infraestrutura; the company responsible for the ‘EBN’ (shipyard and naval base project).