Analysis of strain anisotropy and hydroscopic property of clay and claystone

• The claystone strain anisotropy differs from the anisotropy of modern clay.
• The claystone mechanical properties are sensitive to water content.
• PLAXIS was used to model the stress–strain state of claystone.

The paper presents an analysis of laboratory and field investigations of the anisotropy of natural early Permian claystone deformation behavior. Strain anisotropy in geotechnical engineering is of interest when calculating settlements and the ground base bearing capacity of a building foundation. The authors carried out pressuremeter tests, static stamp tests on claystone having an area of 600 cm2 and a number of laboratory odometer tests of modern hard clay and claystone samples cut parallel and normal to stratification, as well as numerical modeling of these tests. The results obtained from the experiments and numerical modeling of claystone anisotropy deformability are reported and discussed. A number of the field and laboratory experiments made it possible to study the strain anisotropy of claystone in comparison with modern hard clay in the vertical and horizontal directions. In particular, modern clay shows less deformation under loading in the vertical direction than in the horizontal one. As for claystone, it shows less deformation under loading in the horizontal direction. The ratio is obtained to determine the parameters of the Jointed Rock model realized in the PLAXIS software package. The results of numerical modeling are in good agreement with the tests, thus supporting the numerical methods realized in the Jointed Rock model as a practical tool for the analysis of the soft rock stress–strain behavior. The mechanical properties of claystone are sensitive to water content and atmospheric air. Much attention is paid to the fulfillment of engineering and geological surveys, development of design documents, and foundations on claystones.