How is organic soil primarily characterized in terms of its structural properties?

Organic soil is primarily characterized by its very compressible nature. This is largely due to the presence of organic matter, which tends to create a structure that can deform significantly under load. The composition of organic soils often includes decomposed plant material, which contributes to high water retention and a lower density compared to mineral soils. This high compressibility means that when a load is applied, organic soils will compress more than other soil types.

In understanding the other characteristics: low compressibility would suggest that the soil resists deformation and maintains its structure better under load, which does not apply to organic soils. High load-bearing capacity indicates that a material can support heavy weights without failing, which again is not typically the case for organic soils. Finite elasticity would suggest that the material has a specific limit to how much it can deform elastically before permanent deformation occurs, which is not a primary characteristic of organic soils either. Instead, the compressibility is a key feature that defines their structural behavior under various conditions.