9 September 2021
Paimio: a very unusual landslide in Finland
Posted by Dave Petley
Paimio: a very unusual landslide in Finland
Last week a very unusual and interesting landslide occurred close to the town of Paimio in Finland. The image below, published on ts.fi, provides a wonderful overview of the landslide:-
The landslide at Paimio in Finland. Image published by ts.fi.
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Once again I don’t think I’ve seen one quite like this before. The source area appears to be an aggregate storage area from a nearby quarry. The aggregate pile has has clearly failed – there is a scar and some tension cracks visible. The material in the fields appears to be clay, common in formerly glaciated areas. The failure of the aggregate pile has propagated through the clay substrate over a distance of perhaps 100 metres, forming a set of compressive ridges. This is unusual.
It is interesting to ponder what might have happened here. My working hypothesis is that this might be a bearing capacity failure in the clay below the aggregate pile – essentially the clay did not have the shear strength to withstand the stresses imposed by the heap. Its failure caused the pile to collapse.
The nearest comparative event I can remember of the Hatfield Colliery failure close to my now home in Sheffield, in England. In this case colliery spoil was piled on gravels that subsequently failed. However, in the case of the landslide at Paimio the failure has propagated a relatively longer distance from the source, presumable reflecting the properties of the clay.
Fortunately no-one was killed or injured in the landslide at Paimio, and only one building was damaged.
The location of the landslide is, I believe, 60.434, 22.610. There is a Google Earth image of the site from 2018:-
Google Earth image of the site of the landslide at Paimio in Finland.
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Interestingly this image does not show the large pile of aggregate that was involved in the failure, so this might be a comparatively recent addition.
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Acknowledgement
Many thanks to loyal reader Tomi for highlighting this one to me.
Dave Petley is the Vice-Chancellor of the University of Hull in the United Kingdom. His blog provides commentary and analysis of landslide events occurring worldwide, including the landslides themselves, latest research, and conferences and meetings.
The town is called Paimio. Finnish language uses noun cases instead of prepositions and Paimiossa means ‘in Paimio’.
Excellent photo – the compression ridges are very reminiscent of the types you get in peat slides, active layer slides in permafrost and submarine translational slides in clays. That’s possibly the nicest expression of ridging I’ve ever seen. A trial pit cut (safely!) perpendicular to the ridges would show the structure nicely. It’s also interesting how the building is either concave into the main body of the slide or bowing like the ridges (probably the former?).
I can not the image in that link.
I cannot see the image in the link indicated.
Professor Petley, I would encourage you to consult the work of Stig Bernander of Sweden, who has written extensively about downward progressive failure in sensitive clay. That would be my first guess as to what we see in these images.
This type of slide has been common along the Detroit River in Detriot, Michigan. This area is underlain by lacustrine clay. There are a number of aggregate stockpiles as well as steel mill piles of various materials along this river. The rough rule of thumb is that the stockpile along the river should not exceed 10 meters. When they do exceed 10 meters they have had bearing capacity failures that fail towards the river.
Here’s a link to aerial photograph on National Land Survey of Finland website of the location.
https://asiointi.maanmittauslaitos.fi/karttapaikka/?lang=fi&share=customMarker&n=6707860.077843077&e=258497.9480884714&title=Paimio%20Landslide&desc=&zoom=10&layers=%5B%7B%22id%22:3,%22opacity%22:100%7D,%7B%22id%22:2,%22opacity%22:100%7D%5D
Just for info, the Hatfield Colliery tip slid on laminated clays of Glacial Lake Humber, not gravel
Could the – rapid – loading of the heap (starting after 2018) have contributed to the failure?
To fast for the glacial material to equilibrate?
Or could there be an old permafrost horizon that was a weakness in the glacial material?
Could the rapid deposition of the heap contribute to the glacial material failing? Stockpiling begain after 2018.
The glacial material did not have time to equilibrate?
Could an old permafrost horizon be the failure plane in the glacial material?
“Coincidences are rare” (I was taught). Might there have been a water leak near that building that helped precipitate this landslide?
October 4, 2021@9:30a.m. PDT
Really fine illustration with comparable slides. Shows clearly the power of movement through interaction of differing soils and water, or decreasing water. Thank you. Joan S.
Based on the general appearance, the location, and the distance that the slide moved, I would bet my vane shear device that sensitive clay is involved.