Freezing of eight cross-passages of the Rijnlandroute Tunnel in Leiden, Netherlands
ARGE COMOL 5
ARGE JV Freezing Comol 5 consisting of the companies REDPATH DEILMANN and DMI Injektionstechnik
Leiden, Netherlands
May 2020
until December 2021
Project description
An innovative road tunnel with two parallel tubes, each 2.5 km long, was built between the A44 and A4 highways in Leiden. The aim was to improve transport links, create economic impetus for the region and eliminate bottlenecks.
Technical implementation
Ground freezing for the cross passages between the tunnel tubes was carried out using state-of-the-art freezing machines and innovative drilling technology. This method enables a watertight construction by cooling the sandy soil to as low as -25 °C. A stable body of frost forms within 40 days, allowing construction to proceed without water ingress.
"Cold takes time." Once the freezers have been tested and fully commissioned, it takes at least 40 days for a solid body of frost to form, depending on the crosscut.
Maintenance and technology
The freezing machines previously used in Egypt were thoroughly overhauled before being used in the Rijnlandroute project. This shows how important careful maintenance and adaptation of machines is for their long-term use and the specific requirements of new projects.
Innovative design
As part of this project, the drilling was carried out from the first tunnel, even though the second tunnel had not yet been completed. The challenge was to complete the drilling precisely and accurately.
In addition, surface cooling was installed to guarantee a complete frost body as a seal at the target tunnel. This method could significantly speed up future tunnel construction projects.
Construction phase
In the freezing of cross-cuts, freezing pipes are inserted into the ground. A coolant with a temperature of -35 °C circulates through these pipes to cool the surrounding rock or soil to a low temperature. This causes the soil and water in the ground to freeze, creating a stable wall of ice. This ice barrier acts as a temporary support, preventing the ground from collapsing or water from entering the tunnel or crosscut. It thus creates a safe working environment for the construction workers and allows tunnel work to continue.
