Smectite is the biggest offender

Fascinating. From Strange Clay Makes Tall Buildings Rise and Heavy Buildings Sink by Thomas Rye Simonsen.

But then you probably didn’t know that Denmark is home to a special soil type, which makes tall buildings rise and heavy buildings sink.

No one knew that back in the 1940’s either. Back then, engineers watched in shock as Skive Museum rose ten centimeters in a few years. More recently, Banedanmark (which maintains most of the Danish railway network) spent upwards of 200 million Danish kroner (27 million euros) to save The Old Little Belt Bridge, which has sunk 75 centimeters since 1935.

The forces that caused the museum to rise and the bridge to sink all owe to a special soil type known as high plasticity clay, Palaeogene clay or swelling clay. High plasticity clay is probably one of Denmark’s most complicated soil types, and a new research project is now trying to give Danish geotechnicians a much better understanding of its underlying mechanisms.

It is a long article with interesting detail. It rather highlights the complexity of coupled systems. Construction of large structures entails multiple systems and interacts with multiple exogenous conditions. Denmark is a location which strips away many of these sources of complexity.

Denmark has neither volcanic eruptions nor major earthquakes, there are no large rivers causing flooding, and due to the country’s relatively flat terrain there is no risk of landslides.

On top of that, engineers are well-educated and there is a tradition of good construction practice so it’s rare that we see serious damage to buildings, bridges or roads caused by processes underground – fortunately!

But the Danish underground contains soil types that are very different from others. Among these is high plasticity clay, which mostly resembles a semi-hard modelling clay.

The simpler you make the system, the easier it becomes to see the next layer of complexity, in this situation, soil conditions.

If a building collapses in a country with poorly trained engineers, lax building regulations, corner-cutting construction companies, etc., it is easy, and to some degree accurate to ascribe a building failure to those other circumstances and never become aware that there is another, lees obvious factor in play as well. But as you squeeze out the more common sources of failure, you can begin to see more clearly other factors that contribute to failure.

Anyway - interesting.