talajfolyósodás

Talajfolyósodás is a geotechnical phenomenon in which saturated, unconsolidated soil temporarily loses its strength and behaves like a fluid, typically during rapid loading or seismic activity. The process occurs when pore water pressures rise to the point where effective stress drops to zero. Therefore, the soil skeleton can no longer sustain shear stresses and collapses. The condition is most commonly associated with loose sand and fine-grained deposits but can occur in clay‑rich layers under extreme circumstances.

The main triggers are intense earthquakes, rapid loading such as heavy construction, sudden drainage changes, or rapid wetting of previously dry soils. In fragile coastal or alluvial plains, even moderate shaking can induce liquefaction if the soil has a high grain‑size uniformity and is poorly drained. During liquefaction, ground settlements, tilting of structures, failure of foundations and piping, loss of bearing capacity, and lateral spreading can cause significant structural damage. Phenomena such as "lateral spreading" are the classic visible sign of liquefaction in the field.

Detection and assessment rely on site investigations, including borehole geophysical logs, laboratory cyclic triaxial tests, in situ vibration tests, and simulation models. Predictive models use site classification standards (e.g., U.S. Soil Conservation Service factors, UK BS 8004, Australian AS 5100) that consider soil type, saturation level, and seismic intensity. Mitigation measures include drainage improvement, soil compaction, grouting, and deep foundations. In earthquake‑prone regions, planning and code provisions require liquefaction risk assessments prior to construction.