Watertight RD® pile wall to prevent future floods in Arvika municipality in Sweden
January 10, 2019 11:29 CET 6 min read
Municipality of Arvika was hit hard by flood in 2000 when the water rose more than three meters above average water levels and now a new dam is being built to protect the city against future floods. RD pile wall was chosen as a solution to construct the dam. It is partly temporary and partly permanent structure; RD pile wall is part of the dam where the concrete structure is not standing on bedrock. RD pile wall connects the concrete dam to the bedrock keeping the material under the dam in place and stopping water from finding its way between concrete and bedrock.
”RD pile wall was chosen as a solution because it is more flexible and robust, which would minimize the risk for future delays. This was attractive as the project was delayed in the first phase due to difficulties with the bedrock. Another advantage is that jet grouting is not needed”, describes Elin Alsterhag, Technology Manager of Arvika Teknik AB.
SSAB has delivered RD320/12.5 and RD270/12.5 piles with interlocks to Aarsleff Grundläggnings AB, who is the piling contractor for the project. Amount of piles has been over 4 000 meters, in total 450 tons. Construction contractor is NRC Group. The project has been successful; there have been very experienced drillers at the job site. The only challenge has been that the bedrock has been difficult. The project started in August 2018 and the drilling was completed in the middle of December. “We have drilled 345 piles in the pile diameters 273 and 323. Lengths of the piles have varied between 6 and 19 meters in one element. The major challenges have been arising from varying soil and bedrock conditions with a lot of blocks and cracked rocks. The drilling system we used is supplied by Mincon”, tells Patrik Andreasson, Site Manager, Aarsleff Grundläggnings AB.Flood protection is being built by Arvika municipality with Arvika Teknik to protect the city. The flood protection consists of three parts: a main dam between Kyrkviken and Glafsfjorden and two barriers on land. The flood protection will be completed in autumn 2019.
The main dam is a smooth concrete structure across the strait with a frieze of Värmland granite closest to the crest. There are two openings for boat traffic. The boat openings are as wide as the lock in Säffle (8 m) and reaches down to natural bottom depth. The water exchange between Glafsfjorden and Kyrkviken is important for Kyrkviken water quality. For this reason there are three seven meters wide openings in the dam, which ensure the water exchange not deteriorated. Together with the boat openings, these openings provide an area equal to the smallest cross sectional area of the strait. Along with the bottom are pipes through the dam which serves as passage for fish and aquatic animals. The permanent top level is at +48 m above sea level. Throughout the construction period, water is able to flow between Kyrkviken and Glafsfjorden.