Specifics of determining shear strength parameters of rocks. Experimental and analytical methods

The article discusses the key methods to determine the shear strength parameters of rocks such as cohesion and internal friction angle. These parameters are required for solving many engineering-geological problems such as stability analysis for various types of slopes, cut slopes, embankment slopes, quarry walls, as well as for the design of hydraulic engineering structures, etc. Depending on the problem being solved, the determination of shear characteristics can be performed for intact rock specimens, along discontinuity surfaces (joints), or for a rock mass as a whole. We describe three different methods for determining shear strength and obtaining failure envelopes for standard rock specimens. Using limestone from the Moscow region as an example, the results obtained by these different methods are compared. The study considers the key methods for determining shear characteristics along rock joints and presents joint shear test results for metavolcanic rocks from the Far East region. The article demonstrates how cohesion and internal friction angle change with normal stress and, consequently, with depth. A comparison of the shear strength characteristics of metavolcanic rocks obtained by testing of intact specimens and rock joints revealed differences in cohesion by 2-3 orders of magnitude. The paper also discusses the key methods for determining shear strength of rock masses. We present an example of obtaining a failure envelope and calculating cohesion and internal friction angle using the Hoek-Brown model for a metavolcanic rock mass. The dependence of rock mass shear characteristics on the magnitude of the applied stresses is shown.