With 350 trains per day, the Rotterdam – The Hague railway line is one of the busiest in the country. During rush hour, trains even run every three minutes. The rail connection through Delft was therefore a major bottleneck in the west of our country.
The former viaduct over the Buitenwatersloot.
At the end of the previous century it was therefore decided to build a railway tunnel with four tracks. This tunnel, the Willem van Oranjetunnel, consists of two tunnel tubes, the east tube and the west tube, each about 20 m wide with two tracks per tube. To the west of the west tube a 600 m long parking garage was also built with two floors with a capacity for 640 cars.
The construction of the railway tunnel was used to redesign the entire area. The Spanish urban planner Joan Busquets made a plan for this and here you can find a nice overview of all the plans.
The Willem van Oranjetunnel (looking towards Rotterdam) consists of the east tunnel (left), the west tunnel, each with two tracks, and a two-storey parking garage (from Mortier and Jonker, 2014. Tunnel straight through the city centre, Theme article Cement, knowledge platform for concrete constructions).
The Willem van Oranjetunnel starts just north of the Ruys de Beerenbrouckstraat and ends near the Mercuriuspad, opposite the Gamma DIY store and is thus 2300 m long. It passes under the Buitenwatersloot. The track itself is approximately 9 m below NAP . NAP is 43 cm above the water level in the canals (the bosom level). A shallow canal has been made on top of the parking garage so that the streetscape matches that of the old city. As explained elsewhere , this canal is not connected to the surrounding groundwater.
In 2009, construction of the eastern tube began. During construction, train and car traffic along Phoenixstraat and Westvest had to continue, of course, the houses along the railway zone had to remain accessible, and of course no damage could occur to the houses and buildings. That was quite a puzzle, also because there was very little space left to work.
Two construction techniques were therefore used. Approximately half of the tunnel was built in an open construction pit (“cut & cover”). We will not explain this further. The other half, along the Phoenixstraat and around the old and new station, was built using the deep wall method . With this method, you first dig two parallel, narrow, deep trenches in the ground to the desired depth.
Digging the deep wall trench.
These trenches are 1.2 m thick and 3.80 m wide. During the digging, bentonite is poured into the trench so that the walls do not collapse. Bentonite is a so-called support liquid, a mixture of clay and water, also known as grout. Then steel reinforcement is lowered into the trench and the trench is filled with concrete. The bentonite mixture is then pressed out of the trenches from below. These concrete panels are therefore 3.80 m wide. The joint between two adjacent panels is made waterproof with a rubber profile. Here you can see a nice video of the method.
Cross-section of the train tunnel and original location of the original viaduct (from Mortier and Jonker, 2014. Tunnel through the city centre, Theme article Cement, knowledge platform for concrete structures).
Once the walls are in place, the tunnel roof is installed. When the roof is finished, the paving is repaired so that traffic can circulate again. Then the space under the roof is excavated and the railway is laid. This method is therefore called the wall-roof method, or top-down construction method.
The deep walls reach the Pleistocene sand layer at a depth of approximately 20 m. This sand layer is therefore the foundation of the train tunnel and parking garage. The floor and roof of the tunnel are attached to the deep walls and are connected watertight. At the station and city office, the deep walls even reach to a greater depth, so deeper into the sand to obtain sufficient bearing capacity for the buildings. The east tube and the underground station were completed in 2015 and then the trains could run through the tunnel and the other work could begin. After that, things move quickly. The railway viaduct was demolished in six months, the west tube and the city office will be completed in 2017 and the parking garage in 2018. Incidentally, it will take until 2024 before trains run through the west tube, only then will Delft have four train tracks.
The tunnel also goes under Molen de Roos and the Bagijnetoren. Here you can read how they managed that.
