Anisotropy of Strength and Elastic Properties of Lower Paleozoic Shales from the Baltic Basin, Poland

The paper presents the results of laboratory studies on strength–strain properties shales representing four siltstone-claystone lithostratigraphic units occurring in Baltic Basin. Laboratory a triaxial stress state were conducted as single failure tests cylindrical samples oriented parallel and perpendicular to lamination within rocks. Mutually cut out from same drill core sections order determine mechanical anisotropy. Samples characterised by values static Young’s modulus twice high lamination. Similar variability was observed case maximum differential Poisson’s ratio. registered notably lower axial strains, which influenced increased rocks studied are VTI type (vertical transverse isotropy) internal anisotropy rock matrix, significantly influences their geomechanical properties.