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Researchers now know more about why quick clay is so unstable
Quick-clay landslides can be both dangerous and costly. Researchers can now see what happens at the nano level.
Quick clay is actually ancient seabed. The clay formed under water, but came to the surface when the landscape rose after the last Ice Age.
This clay was not so dangerous when it was full of salt from the sea.
Only when the salt in the clay was washed out by fresh water from rain and groundwater did it turn into quick clay.
But what exactly makes quick clay so unstable?
New research from Ge Li and Professor Astrid Silvia de Wijn, both at NTNU, looks at what happens at the nano level when the clay weakens because fresh water replaces salt water.
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“We have made very detailed and careful simulations of the friction between clay particles,” says researcher Ge Li at PoreLab and NTNU's Department of Mechanical Engineering and Production.
Important to understand quick clay
This work is particularly important for us in Norway. A large number of people live on quick clay, many of them in Eastern Norway and Trøndelag.
But there are also significant amounts of quick clay in Sweden, Finland, Canada, Russia, and Alaska. The research is therefore important for many more people.
“We see that the ions in the salt water settle on the surface in certain places and make it more difficult for the clay particles to slide against each other. In other words, the ions make the surface uneven and stand in the way of slippage,” says Ge Li.
Ions are electrically charged atoms or molecules. In this case, the ions from the salt help to keep the clay stable.
Dramatic and costly consequences
Building on quick clay can have dramatic consequences.
In 2020, a clay slide in Gjerdrum took 31 housing units with it. Ten people died in the landslide, while ten others were injured. Around 1,000 people had to evacuate their homes.
A quick-clay landslide in Levanger in August 2025 took parts of the E6 highway and the Nordland Line railway with it. One person died. Several months later, both the road and the train line are still closed.
This has cost society several million every day.
Want to find a gentler alternative
Stabilising quick clay is both expensive and can have significant consequences for the environment.
“When we stabilise quick clay today, we mix and inject lime and cement. But we don’t really know how it works. The production of lime and cement also emits a lot of CO2, which is not good for the environment,” says Ge Li.
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You might think it would be possible to inject the quick clay with salt instead. In the lab it may look that way, but this will not work in practice.
“However, our hope is that by better understanding how the salt works, it will be easier to find better and more environmentally friendly ways to stabilize quick clay,” says Ge Li.
Reference:
Li, G. & de Wijn, A.S. Molecular dynamics simulations of nanoscale friction on illite clay: Effects of solvent salt ions and electric double layer, Journal of Colloid and Interface Science, vol. 703, 2026. DOI: 10.1016/j.jcis.2025.139107
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Read the Norwegian version of this article on forskning.no
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