One day a car fell down a hole

One day in 2007 a car fell down a hole in the paving of a parking area outside a shopping mall in the Swedish city of Norrköbing. The sand and gravel securing the stability had disappeared through leaks in a DN 2000 mm concrete pipe that is part of a 440 m long culvert under a brook. The pipe was constructed more than 40 years ago and is located 8 m underground. The pipe is placed partly under one of Norrköbing’s busiest traffic centres and partly under the parking area where the hole suddenly appeared.

Aarsleff Pipe Technologies quickly established that it was out of the question to renew the pipe by using traditional excavation techniques, as it was not possible to establish bypass pumping for moving water from a DN 2000 mm pipe with full flow.

 We decided that the ideal solution was Aarsleff Segmental Lining, which meant installation of prefabricated glass fibre segments inside the existing pipes. By using Aarsleff Segmental Lining, we could, among others, minimise bypass pumping of the water running in the brook during the working period.

We used segments which varied in length from 0.5-2.3 m. However, before we could initiate the renewal process we had to establish two 8 m deep excavations from which the actual installation would take place. We then cut off the upper part of a 4 m section of the concrete pipe, and subsequently we lowered the new segments down into the pipe, where we placed them on a trolley that moved them into the right position inside the pipe. Here we joined them. Finally, we injected grout into the space between the old pipe and the new pipe.

The entire renewal process took only 30 days. The result was a new pipe with a diameter of 1800 mm.