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A year ago, a large rockslide occurred on the E18. Veivesenet now claims that 40 rock cuts must be better secured along the highway through Vestfold.
December 17, 2019. Veivesenet blows up a large rock on the E18 in Bommestad, near Larvik. The landslide that arrived here four days earlier put a stop to Veivesenet. Photo: Terje Bendiksby / NTB
The Larvik section had recently been opened and suddenly large stones fell onto the busy highway. No lives were lost, but the landslide shocked both motorists and the Norwegian Public Road Administration. The highway company found that the work they had done to ensure the rock cutting was too bad.
A rock cut is a rock wall or rock slope that is made through physical intervention when building roads and railroad sections.
Bygg.no can now report that Veivesenet has since verified the 111 cuts in the mountain sections on the E18 between Sande west of Drammen and Langangen in Telemark. In recent years, many new highways have been built here. Result: Up to 40 locations must be secured.
– We have neglected ourselves, admits project manager Tore Jan Hansen at Veivesenet to Bygg.no.
Typically, older rock cuts along Norwegian roads pose a greater risk than newer ones. This is what one of the country’s leading experts on the matter tells Aftenposten. He does not rule out that there are more landslides of this type.
This is what the landslide in Bommstad near Larvik looked like:
Several mistakes were made
After the landslide in December 2019, road director Ingrid Dahl Hovland created a group of experts to find out what happened.
The group’s report lists a number of issues worthy of criticism:
- The 30-meter-high rock cut was described in advance as a location that might require additional security measures.
- The bolt fastening that was carried out during construction was “clearly poor.”
- A stability analysis was not carried out as required by Veivesen’s own manuals.
- But also “unfortunate circumstances” related to weaknesses in the mountainous area contributed to the landslide.
NTNU professor Bjørn Nilsen led the group of experts.
He was also hired as an expert following the dramatic E18 Hanekleiv tunnel landslide on Christmas Day 2006. The investigation report at the time concluded that Veivesenet at Vestfold had minimal, if any, experience in the tunnel construction when commissioned to build. Hanekleivtunnelen.
The investigation led to the closure and security of a large number of tunnels in the county.
NTNU professor Bjørn Nilsen (far right) has led the work to analyze what caused the landslide in Bommestad. He is shown here outside the Hanekleiv tunnel in Vestfold in December 2006. Television civil engineer Per Bollingmo from Multiconsult. Photo: Per Annar Holm
– Bommestad a warning for us
There is also great seriousness about the reinsurance that is underway after the landslide in Bommestad near Larvik.
– The landslide was a warning to us. This is an area in which we have neglected. We have to be honest about it, says project manager Tore Jan Hansen.
It explains the need for reinsurance in 40 places with “some weaknesses during development.” But above all, Veivesenet hasn’t focused enough on maintaining rock cuts, he says.
Hansen says such cuts are affected by everything from rain and frost to the sun, as well as roots that grow and put pressure on the rock. In the worst case, this causes the rock masses to pop out, as happened in Bommestad.
The photo was taken three days after the Bommestad landslide on December 18, 2019. Veivesenet is working to clean up and secure the area. Photo: Alexander Therefore
It will take three years to insure everywhere
The Ministry of Transport and Communications has distributed large sums to keep contractors afloat during the crown crisis. Thanks to this money, reinsurance along E18 is in full swing.
At the moment Veivesenet is working in Holmenåsen south of Sem. Here’s a 750 meter cut.
According to Tore Jan Hansen, securing the 40 points could cost NOK 50 million. 25 people do the actual work. Now it takes place 24 hours a day, seven days a week. It will still be three years before all the venues are insured, Hansen says.
As much as possible, Veivesenet tries to avoid flying blocks to secure cuts. Most of the work is done with bolts.
No more landslides can be ruled out
Aftenposten has asked Bjørn Nilsen if we should expect more landslides of this type on Norwegian roads. Not least as a result of climate change.
– We can’t rule that out. And the risk is probably higher with old rock cuts than with new ones. They were built with other methods and with less strict rules than the current ones, says Nilsen.
– In general, the new cuts hold up pretty well. We have been given more stringent requirements and guidelines on how they should be done. For the elderly, there is continuous monitoring that will prevent these types of incidents, says Nilsen.
