ABSTRACT
The true stress–strain behaviour of soil is discussed. The behaviour involved the elastic–plastic and fully elastic behaviours. Stress–strain responses of various soils are presented. The similarities of soil responses in the stress–strain and consolidation curves are compared and the unique behaviour that the soil always remembers the past maximum pressure that it has been subjected to is highlighted. The distinctive physical meaning of the elastic–plastic and the elastic soil responses is illustrated graphically to ease the understanding of these basic responses of soil to stress. Then the three testing phases involved in the consolidated drained and consolidated undrained triaxial tests are explained followed by the basic steps involved in deriving the conventional soil linear failure envelope. Perhaps, the true soil failure envelope is non-linear with zero cohesion intercept according to effective stress analysis. Thence, the various non-linear shear strength equations that have been introduced by geotechnical engineering researchers are presented. This chapter also demonstrates how the linear failure envelope could be reinterpreted as a non-linear failure envelope. Finally, non-linear failure shear strength envelopes of various soils with zero cohesion intercept are presented to emphasise this true shear strength behaviour of soils.
