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Quick Clay Landslide Norway Dec 30, 2020


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aabel

In the middle of the Christmas Night at 0400 hrs (4 AM) the landslide wiped away the ground under a part of a village near Oslo. When daylight came at around 9 o`clock AM, some 20 buildings was down in the quick clay or on their way down the some 700 meters long and 300 meters broad landslide. Daylight is only some 6 hours from 9 AM to 3 PM in the area.

Helicopters manage to lift up and out 13 persons from drifting areas in the slide. Drones and helicopters were  seeking day and night over the floating clay with some remains of houses and constructions here and there. 10 people was still missing.

After some 3 days rescuers made paths of light materials, Styrofoam, and started to break in to the houses. Special trained dogs marked where people could be located.

As I am writing this, nearly 5 days after slide, they managed to find 7 out of the 10 missing. Unfortunately all 7 dead.

 

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to_dave007

This is a good documentary about this quick clay.

 

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aabel

Thanks 007, the video is very informative about quick clay landslide. In 1893 "Verdalsraset" in Mid Norway costed 116 persons lives when some 3 sqkm with 55 million cubic meters wiped away 105 farms to the sea.

UPDATE DAY 6 after the main slide: it is still 3 persons not found. Rescue teams still searching day and night. At the end of day 5, yesterday, they manage to rescue a dog alive from the inner of the ruins. The small dog had survived in an air pocket inside one of the 14 buildings with 31 apartments.

HOPE of finding people alive is still the reason for the continues hard and risky work of the teams struggling inside the former buildings.

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to_dave007

This video is not an quick clay landslides..  but it's related..  as it shows the recovery of an excavator that has sunk in blue clay in Sweden. The stuff looks VERY difficult to work with.

 

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aabel

Very correct. It is not a slide because it is flat land. The quick clay has no way to go downhill. But the material is the same. Rather solid as long as it is untouched, not overloaded or not washed out by fresh water. When shaken or washed, it all in a sudden turns from a consistent as weak concrete to like sour cream.

The reason is that this micro small "stones" in the clay is like magnets as long as they are stable in salt circumstances - as they were when put there by a Glazier in salt water as a part of the ocean - some hundreds of thousands years ago.....  

As I was working in the Oslo area in the 1970s, we half drowned an excavator Akerman H12 similar to the excavators in the video. 

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to_dave007
30 minutes ago, aabel said:

Very correct. It is not a slide because it is flat land. The quick clay has no way to go downhill. But the material is the same. Rather solid as long as it is untouched, not overloaded or not washed out by fresh water. When shaken or washed, it all in a sudden turns from a consistent as weak concrete to like sour cream.

The reason is that this micro small "stones" in the clay is like magnets as long as they are stable in salt circumstances - as they were when put there by a Glazier in salt water as a part of the ocean - some hundreds of thousands years ago.....  

As I was working in the Oslo area in the 1970s, we half drowned an excavator Akerman H12 similar to the excavators in the video. 

We have a lot of clay deposited at the bottom of old glacial lakes in Ontario Canada too..  but to my knowledge none of it has the same properties as this quick clay. 

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aabel

Without being a specialist, I would guess that it has to do with the content of minerals in the clay. Some kind leads electricity, others less and may be some not at all. It would be interesting if someone could tell if quick clay have an electromagnetic function as long as it is stored in salt water.

In seawater at the coast of Norway my company once had to remove clay for fundaments of a bridge at a depth of som 15 meters. The clay was hard as concrete and mixed with round stones. We called it over consolidated clay.

 

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aabel

JUST NOW, 6.5 day/nights after the landslide; RESCUE STOPPED. NO LONGER HOPE TO FIND PEOPLE ALIVE.

Seven found dead. Search for the 3 missing will continue with downscaled intensity.

Four years ago a similar quick clay landslide happened in a forest area  some 40 kilometers away from this one. 3 forest workers was into the slide.   One of the 3 was found dead. The two others are still buried in the quick clay.

Quick clay is a very difficult grave to get access to..........

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A LITTLE MORE ABOUT QUICK-CLAY. Particles are so small there goes some 100 of them in a with of a hair. They consist of silicate minerals, mostly Illit and chlorite shaped as thin flakes or rods.

When they were sedimented in sea water under glaciers ten thousends of years ago, they formed structures as card houses filled with salty sea water. The minerals were electronic negative. And the salty sea water with natrium ions was positive. So the structure stick together as magnets. As long as the salt is not washed out.

It can be stabilized by adding calcium and magnesium.

More info: "Quik-clay landslide mitigation using potassium chloride (Helle, T.E.)

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