Correlation between structure of intact loess and gas permeability

The isotropic compression tests with simultaneous gas permeability measurements are performed for intact loess with various water contents in three regions. The behaviours of compression deformation and change of induced gas permeability of intact loess are analyzed. The correlation between gas permeability and compression deformation is discussed. The formula of compression curve of intact loess is proposed to characterize the compressive deformation under the coupling of moisture and stress, in which the structural parameter defined by gas permeability is included as a known parameter. The results suggest that changes of gas permeability of intact loess are found to have a good correlation with volumetric deformation during isotropic compression tests. The structural potential difference of intact loess caused by the fabric and moisture and its damage induced by the stress can be reflected by the change in gas permeability. The gas permeability ratio corresponding to the yield stress at the ratio of a certain water content to the reference water content is defined as the structureal ratio parameter, and it is introduced into the isotropic stress variable to lead to a normalized compression curve of intact loess with various water contents. Regarding the compression curve at the reference water content as the reference state, a unified and continued description of the compression deformation before and after yielding for unsaturated intact loess is proposed, and the calculated results agree well with the test ones.