75 jaar Imbema

Renovation Velsertunnel: creative solution results in a time saving of 50% on the construction of an asphalt joint in the tunnel

Part of the major renovations carried out on the Velser tunnel a while ago included renovating the asphalt which included constructing the asphalt joint, inside and outside the tunnel. In the tunnel, bitumen tape was used to construct a joint between the concrete walls and the asphalt. This was done using a machine, after a creative solution had been found for dealing with the drainage holes in the barriers.

This article was published in the March 2019 edition of GWW Totaal.                                

read the article from GWW Totaal

The challenge: drainage holes in the Velser tunnel

The contract was to install a bitumen tape asphalt joint in the renovated Velser tunnel. Bitumen tape ensures that there are no gaps between asphalt and concrete and that expansion and contraction caused by cold or heat are absorbed properly.

The part of the asphalt joint outside the tunnel was easy to construct. It was the part inside the tunnel that presented a major challenge. The reason: the tunnel has drainage holes for water at the bottom of the concrete wall at 2-metre intervals. This is, of course, a logical feature as a tunnel collects a lot of rain and waste water. How can you apply bitumen tape quickly and neatly in this situation?

Maurice Wolf, Specialist Road Construction Products at Imbema explains:

“I have been supplying asphalt products to road builders for years. The application for this project was received by InfraSupply – the company I was working for at the time – and related to the application of a TOK® tape asphalt joint for the Velser tunnel. I always purchased these materials from Imbema, my current employer who I had worked closely with for years. Together, we advised the customer to use a machine to apply this bitumen tape, both inside and outside the tunnel, as it would save a lot of time, manpower and therefore money.”

Asphalt joint inside and outside the tunnel

The part of the asphalt joint inside and outside the tunnel was constructed in two phases. Some of the work was carried out at the weekend so that on Monday, the asphalt team could work on the surface layer.

The work inside the tunnel was complex. Each section of the Velser tunnel is 768 metres long, which means that a total length of more than 3 kilometres of bitumen tape asphalt joint had to be applied. It would have taken an extremely long time and been extremely labour-intensive to do that by hand, hence the suggestion to use a TOKOMAT® machine to do the job, despite the obstacles in the tunnel.

Maurice: “The drainage holes in the barrier at 2-metre intervals were a complication. Would the TOK® tape stay stuck down if you could only apply it in such small pieces? How were we going to cover such a long distance without having to stop every 2 metres? The project presented quite a challenge…”

Would the machine be able to cope with those drainage holes in the barriers? Could the TOKOMAT® machine complete the job in one go, without having to stop at every drainage hole? If it kept having to stop, it would take a lot longer and you would keep having to start off again and work out where to start from.

The solution: work together on smart solutions

The time pressure on the renovation of the asphalt and the unique situation of the tunnel called for a creative solution. Maurice came up with a technical solution: an additional support wheel that would run against the wall instead of just having one wheel on the ground. This would enable the nozzle (that applies the bitumen tape) to be kept in a constant position.

We teamed up with the customer and got going on the job: while the machine was in operation, workmen cut away the surplus bitumen material that had been applied over the holes. By working in this way, the TOKOMAT® machine was able to complete the whole job in one go.

“Things were tense when we started the job… no-one knew whether it was actually going to work! After the first 10 metres, everyone was able to breathe a sigh of relief: the method was working! It was a fine example of successful collaboration. I had adapted Imbema’s machine in such a way that the TOKOMAT® machine was able to remain stable, even when it had to pass over the holes,” explains Maurice.


Maurice: “The result in the tunnel looked very slick, there were no points where the machine had had to stop and start, and application had been carried out in one continuous process. The section was completed in one go. While the job had been scheduled to take two days, it ended up only taking one day to complete.”

 “What I found so remarkable about this project was the way that everyone worked together. The job of constructing the asphalt joint is often one that is left till last: it has to be done but always under time pressure and between the other activities. In this case, the collaboration was flawless. Everything was well-prepared. The workmen who were cutting off the surplus pieces of bitumen tape were standing at the ready and together we completed the job. It was really remarkable!”

To find out more, go to: www.imbema.com/wegenbouw

Maurice Wolf

Maurice Wolf

Specialist Black Products
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