In Rotterdam (The Netherlands), the De Groene Boog consortium, of which BESIX NL is part, is currently connecting the existing A16 and A13 by constructing a new motorway. This new 11 km long piece of A16 will be the world’s first energy neutral motorway with tunnel and will significantly improve the accessibility of Rotterdam. Playing an essential role in the realisation of this impressive project is BESIX’ in-house Engineering department. Time to take a closer look at their indispensable contributions to the project!
1. The Incremental Launching Method across the Terbregseplein
Amongst the masterpieces is the flyover, a 400-metre long viaduct that passes over a railway line and a motorway interchange. As closing these busy traffic lines was out of question, the consortium opted for the Incremental Launching Method. Experts at BESIX Engineering were responsible for its design, in collaboration with GRID International Consulting Engineers S.A. from Lisbon, and are now assisting the operations teams with the implementation.
How does this work? First, abutments and piers are built. Behind the northern abutment, where a temporary production line was set up, each segment (about 30 m long) is cast in relation to the previous one. Then, the segments are gradually pulled over the Terbregseplein, until the whole structure reaches the southern abutment. This launching method happens at a very low pace, i.e. 2.5 m per hour; this cannot be observed by the vehicles driving under the viaduct. As this method is happening literally in the air, traffic is enabled at all times.
An imposing blue steel structure, called the launching nose, was installed at the front of the first segment to balance out the weight equally and limit the internal stresses as the structure cantilevers over the existing infrastructure. BESIX Engineering went through all the steps in advance with specific calculation methods and are now monitoring forces and deformations. It’s millimetric work and unprecedented for a concrete construction.
Watch how the fly-over moves over the Terbregseplein in this timelapse.
2. The energy neutral Rottemeren Tunnel
Another feat of engineering, and a remarkable case of the combination of several BESIX Engineering expertise, is the Rottemeren Tunnel, a 2.2 km long semi-underground tunnel which runs under the Lage Bergse Bos and the river Rotte. To minimise the disturbance for the environment and to keep navigation on the Rotte enabled at all times, the consortium opted for underwater concrete.
How does this work? The teams first install the sheet piles and foundations, so that they can excavate the tunnel without influencing the ground water level. Then, the reinforcement and concreting of the floor are carried out, both underwater. When the concrete is strong enough, the water is pumped out to create a dry construction pit in which the rest of the tunnel segment is built. Thanks to this method, less concrete is required, which in return reduces the CO2 emissions.
Parametric Design. The tunnel is a good example of BESIX Engineering’s parametric design. This involves automating digital design processes through algorithms and computer programming, thanks to which the design of a single segment could be automatically reproduced along the entire length of the tunnel. The automation reduces the risk of errors and saved the engineers time to study alternative design solutions. That way, the teams came to an optimal design with reduced material quantities.
BIM model & digital twin.A BIM model was created which integrates all the elements and is used to automatically generate drawings. The BIM model was then turned into a virtual reality model, which is called TWIN-16. This model includes the functional behaviour of the installations which enables the virtual testing of all system behaviours. This in turn creates trust towards compliance of stakeholder requirements in an early phase, which saves time and money for later test phases and long-term maintenance.
3. Sustainability
The last element that is worth mentioning is the focus on sustainability. As the A16 will be a completely energy neutral highway, all the energy needed for the roads and tunnel will be generated naturally, in this case through solar panels. In addition, the consortium takes a number of measures during the construction to minimise the emissions as much as possible.
For example, crews are using all-electric machinery, including heavy excavators, telehandlers, asphalt machines, and a lifting crawler crane. Only recently, the teams also successfully tested an electrical crawler crane which can operate unplugged for 10 hours! This crane has a load capacity of 50 tonnes and a hook height towering up to 43 metres. It’s the first time in the world that heavy equipment like this one operates on a jobsite with this high level of autonomy.
Lastly, Hydrotreated Vegetable Oil (HVO) fuel is used on a large scale on the project (over 4 million litres). This rather new HVO fuel serves as a replacement for diesel and is produced from food industry residues. The difference with diesel? It has 90% fewer emissions, so it’s fits perfectly in the sustainability level the teams are aiming at!
