A dynamical systems-based approach to soil shear

This note models monotonic soil shear as a dynamical system. It provides additional information to support the hypothesis that for monotonic soil shear, the rates of change of the shear stress, effective normal stress and void ratio are proportional to the applied shear and effective normal stresses with the proportionality values decaying with strain to become zero at the steady-state condition. This hypothesis provides close fits to stress–strain–void ratio curves from undrained shear tests of uncemented, resedimented clays and drained shear tests of uncemented sands and silts, using triaxial and true-triaxial equipment, and various stress paths. For undrained shear, model parameters vary smoothly with over-consolidation ratio; for drained shear, they vary in an orderly way with relative density. The model's value lies in that a well-formed hypothesis, derived from the steady-state condition, provides a simple, alternative approach to current complex elastoplastic models based on critical state theory.