The paper presents the investigation results to determine the mechanical characteristics of multilayered shales. The results are based on shearing and breaking off tests along certain planes of specimen. The modified Mohr-Coulomb criterion including an alternating angle of internal friction and variable cohesion is used as a strength criterion. Both the angle of internal friction and cohesion are considered as parameters depending on orientation. To determine the transverse strength at different orientations three rock test designs and two equations are proposed. In the case of breaking off the rock another strength criterion proposed by G.Geniev is used. It was investigated by authors of the paper for various anisotropic materials. Here strength characteristics are determined via calculations. They are based on results of two simplified tests (along and across the foliation), that is simple stretching test or the so-called "Brazilian test". Examples of calculations of the rock strength characteristics using the proposed models are given and considered in a critical manner.

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