The document discusses shear strength of soils and methods for determining shear parameters in the laboratory. It introduces the Mohr-Coulomb failure criterion, which represents the shear strength of a soil as a function of its normal stress. Direct shear tests and triaxial shear tests are described as methods to experimentally determine the cohesion and friction angle parameters that define the Mohr-Coulomb failure envelope. Graphs and equations are presented to illustrate the relationship between shear and normal stresses at failure for different soil types based on these parameters.
