Coen Tunnel Amsterdam
As part of the expansion of the Coenplein junction in Amsterdam, Concrefy was commissioned by Coentunnel Construction VOF to carry out inspections at the First Coen Tunnel, and to perform materials research.
The purpose of the inspection of the tunnel was to determine the remaining life cycle for establishing future use and required maintenance work. The research focused mainly on the penetration of chlorides in the concrete structural parts with a view to possible chloride-initiated reinforcement corrosion.
The First Coen Tunnel is part of the A10 motorway in western Amsterdam. The tunnel under the North Sea Canal was inaugurated in 1966. Construction involved what is known as an immersed tube. This method of construction means that the tunnel segments are manufactured in a dry dock and sealed off temporarily. Then the segments are floated to the site and sunk into place. Once the individual segments have been coupled to each other, a waterproof tunnel is formed.
lenght of segments
total lenght of the First Coen Tunnel
lenght of tunnel fully covered
The tunnel consists of segments that are 90 m long. The total length of the First Coen Tunnel is 1283 m, of which 587 m is fully covered. The tunnel consists of two tubes separated by an intermediate corridor. The corridor can be used as an escape route in the event of an emergency. The west tunnel is used for traffic from Zaandam to The Hague, while the east tube is used for traffic travelling in the opposite direction.
Inspection on location was carried out over two nights when the tunnel tubes were closed for maintenance. Cylinders were drilled at different locations in the tunnel, taken from the deck and out of the wall. At the same time, measurements were taken to determine the concrete cover of the reinforcement in the vicinity of the drilling locations. The tunnels were also visually inspected to determine if there was any frost damage.
The cylinders were then tested with respect to chloride profile and concrete structure in the Concrefy materials science laboratory. On the basis of the results of laboratory tests, the analysis of rebar detection and the results of the visual inspection, an analysis for the remaining life of the concrete structure was created.