The Pannerdensch Canal tunnel

Construction of this dual rail tunnel below the Pannerdensch Canal was part of the “Betuwe” project, a new rail line designed to convey merchandise between the port of Rotterdam and Holland’s border with Germany. This 160-kilometre line can accommodate container railway cars. The work package assigned to us called for the design and construction of the Pannerdensch tunnel, a 6.3-kilometre structure. The project included construction of a dual bored tunnel 1,620 metres long (8.5 metres in inner diameter), portals and access ramps over a distance of 1,200 metres, and 3.3 kilometres of railway platform made from backfill material. In addition, the Pannerdensch Canal tunnel possesses a special feature: it is equipped with gates (square cofferdams) at either end designed to prevent flooding.

BACKGROUND

The Pannerdensch Canal is located close to Holland’s eastern border. On Dutch soil, the Rhine splits into two to form the Waal and the Pannerdensch Canal. Formerly, the river played an important role in the defence of the Republic of the Netherlands as it formed a natural barrier and could be used to transport troops and materiel. In the 17th century,  as a result of sediment build-up and silting in the Rhine, French forces under Louis XIV were able to cross the river and cause trouble in the Republic in 1672. These events led to the construction of the Pannerdensch Canal, which was completed in 1708.
Nearly 300 years later, a new crossing was planned. The contract awarded to a consortium consisting of Campenon Bernard and Dumez-GTM (VINCI Construction Grands Projets) called for construction of the Pannerdensch Kanaal bored tunnel, which was the third and final work package for the new “Betuwe” railway line.

TECHNICAL OVERVIEW

The tunnel is located between the breakwaters of the Pannerdensch Canal. The passageway that runs under each breakwater includes a technical building designed to accommodate the tunnel’s technical equipment and vertical gates that can be lowered to ensure watertight conditions in the event of an emergency. On the eastern bank of the Canal, excavation operations had to take into account a former sand pit extending deep into the ground.
The tunnels were bored using a slurry shield TBM 9.5 metres in diameter. One of the difficulties was crossing under the Canal with only five metres of overhead coverage and, as a result, extremely careful monitoring of the confinement pressure. This reduced gap enabled us to optimise the length of the tunnel as a whole given slope restrictions for rail traffic.
At their deepest point, the tunnels are equipped with a pumping system that is connected to the surface by a cylindrical shaft (roughly 25 linear metres) which was created using the cutting method from the natural ground down.
Given the high water level, 18 construction cofferdams were deployed. They consisted of provisional sheet piling, highly resistant piles, and immersion concrete. Construction began with the driving of the sheet piling. The piles were then driven from ground level. The piles were made from precast prestressed concrete with steel ground anchors for the deepest parts.
The main concrete structure was erected in two stages of 25-metre cycles. The first stage was to create the foundation slab and the second, to build the walls and roof in a single pouring operation using a cooling system. Construction was completed by backfilling the cofferdam, removing the sheet piling, and carrying out finishing work. In the deepest cofferdams, steel fibres were added to the immersed concrete for greater resistance to water pressure. In the event of concrete cracking, the steel fibres bend and create resilient elastic joints.
The bored tunnel consists of reinforced concrete ring segments 1.8 metres long placed sequentially by the TBM. The segments were prefabricated in a manufacturing plant in Germany, about 100 kilometres from the worksite.

The client had direct online access to settlement data captured and monitored by sensors deployed at 25-metre intervals.

IMPACT

For environmental reasons, this project called for construction of a tunnel rather than a bridge.
Construction of the new Betuwe railway line was designed to relieve congestion on existing rail lines, which were considered to be saturated and unable to meet current transport needs.
This new infrastructure facilitates the transport of merchandise between the port of Rotterdam and the border with Germany, thereby reinvigorating trade between the Netherlands and Germany.
This new line, which also includes two other bored tunnels (the Botlek and Sophia tunnels), is 160 kilometres long. It can accommodate two-level container railcars and it helps relieve congestion at the port de Rotterdam, helping it maintain its position as a leading international seaport.