Puristusindeksi

Puristusindeksi, often translated as compression index, is a dimensionless parameter used in geotechnical engineering to describe the compressibility of a soil sample. It is a measure of how much a soil's volume decreases under sustained load, particularly in the context of consolidation. The puristusindeksi is typically determined from laboratory tests, such as the oedometer test, where a soil specimen is subjected to increasing vertical stresses and its settlement is measured over time.

The puristusindeksi is a key component in calculating the settlement of structures built on compressible soils like clays. A higher puristusindeksi indicates that the soil is more compressible and will experience greater settlement under load. It is usually determined from the void ratio versus the logarithm of the applied pressure curve obtained during the consolidation test. Specifically, it is the slope of the normally consolidated portion of this curve.

The value of the puristusindeksi is influenced by factors such as the soil's mineralogy, particle size distribution, and initial void ratio. It is an important parameter for engineers designing foundations, retaining walls, and other structures where understanding and predicting soil settlement is critical for safety and performance.