Förvätskning

Förvätskning is a Swedish term that translates to liquefaction or fluidization in English. It describes a process where a solid material, typically a granular substance like sand, soil, or ash, behaves like a liquid. This phenomenon is most commonly associated with earthquakes. During seismic shaking, water trapped within the pore spaces of saturated granular soils can be compressed. If the shaking is intense enough and the soil has poor drainage, this pressure can increase significantly, exceeding the weight of the soil particles above.

When this occurs, the water pressure essentially lifts the soil particles, reducing the friction between them. The soil loses its structural integrity and strength, and can no longer support the weight of overlying structures. This results in the ground behaving like a fluid, causing buildings to sink, tilt, or collapse. Liquefaction can also occur in situations other than earthquakes, such as during rapid loading or impact events, though seismic activity is the most prevalent cause.

The susceptibility of a soil to liquefaction depends on several factors, including the grain size distribution, density, degree of saturation, and the intensity and duration of shaking. Fine-grained sands and silts with a moderate to high water table are particularly vulnerable. Mitigation strategies for liquefaction include soil improvement techniques like compaction, deep soil mixing, or the installation of stone columns to reduce water pressure and increase soil strength.