Unloadingkäyrä

Unloadingkäyrä, also known as the unloading curve, is a graphical representation used in the field of geotechnical engineering to illustrate the relationship between the vertical effective stress and the void ratio of a soil sample during unloading. This curve is a crucial tool in understanding the behavior of soils under various stress conditions, particularly in the context of soil mechanics and foundation engineering.

The unloadingkäyrä is typically derived from laboratory tests such as the one-dimensional consolidation test or the oedometer test. During these tests, a soil sample is subjected to a series of loading and unloading cycles. The unloading phase occurs when the applied load is reduced, causing the soil to expand and the void ratio to increase. The effective stress, which is the difference between the total stress and the pore water pressure, decreases during unloading.

The shape of the unloadingkäyrä can provide valuable insights into the soil's compressibility and its ability to recover from stress changes. A steeper unloadingkäyrä indicates a more compressible soil, while a flatter curve suggests a soil that is less compressible and more resilient to stress changes. This information is essential for designing foundations, embankments, and other structures that interact with the soil.

In practical applications, the unloadingkäyrä is often used in conjunction with the loadingkäyrä to create a complete stress-strain relationship for the soil. This comprehensive understanding is vital for predicting soil behavior under different loading conditions and for ensuring the stability and safety of engineered structures.