jännenehiekka

Jännenehiekka is a Finnish term that translates to "tension sand" or "stress sand." It refers to a specific type of sand that exhibits peculiar behavior under certain conditions, most notably when subjected to vibrations or pressure. This phenomenon is not a distinct geological material but rather a description of how certain sands behave when their internal structure is disturbed.

The behavior of jännenehiekka is a result of the interlocking grains and the air pockets between them. When a uniform load is applied to a dry sand, it can support the weight. However, if that load is applied dynamically, such as through vibration, the sand particles can momentarily lose contact with each other. This causes the sand to lose its stiffness and behave like a liquid, a process known as liquefaction. The trapped air within the sand is expelled, leading to a temporary collapse of the granular structure.

This effect is more pronounced in fine-grained, uniformly sized sands with low clay content. It is a critical consideration in civil engineering, particularly in earthquake-prone areas, where the liquefaction of soil can lead to catastrophic structural failures. Understanding and predicting jännenehiekka behavior is essential for designing stable foundations and infrastructure. While the term itself is Finnish, the phenomenon of sand liquefaction is recognized and studied globally under various names.