Physical Similitude and Structural Collapse in K₀ Compression of Soils

The uniaxial ( K₀) compression of several soil types (loess, limestone powder, cemented sand) is analyzed with special reference to the instability phenomena. According to the K₀ dependence on the axial stress, two kinds of behavior may be discerned: physically isomorphous ( K₀= const) and anisomorphous ( K₀≠ const). The first alternative is confined to the semilogarithmic compression law and exists within a certain interval of behavior. Different sorts of discontinuities in the uniaxial stress path are illustrated by experiments with cemented sand, sagging loess, limestone powder, and brickearth. The dependence of soil structure on the principal state parameter stress takes the form of a gradual destruction of natural brittle bonding, adhesive bonds, and of changes in the fabric and internal stress. The effects can be directly described by a “residual” stress representing the main internal variable.