Behaviors, constitutive models and numerical simulation of soils

According to the degree of influence on stress-strain relationship, soil behaviors can be categorized as essential behaviors, expressional behaviors and relative behaviors. The essential behaviors including compressive hardening, dilatancy and friction are those fundamental characteristics differing soils from other continuous materials. The expressional behaviors include such as stress history dependence, stress path dependence, softening, anisotropy, structure, creep, particle crushing, and temperature effect. They indirectly influence the stress-strain relationship of soils through affecting the essential behaviors of soils. The relative behaviors consist of such as yielding, normality flow, associated flow, coaxiality, and critical state. They are basic concepts or assumptions to be incorporated into an elasto-plastic constitutive model if such model is desired. Following a detailed discussion on the soil behaviors and their mutual relations, a comprehensive review is provided on a few representative constitutive models, e.g., the Duncan-Chang nonlinear elastic model, the Cam-clay elastio-plastic model and the UH model, the Asaoka model, the Li-Dafalias model, the Yin-Graham EVP model and other constitutive models developed by Chinese researchers. The focus is placed mainly on how to conceptualize the intrinsic soil behaviors and lead to constitutive models, and which behaviors can be reflected by each constitutive model and how. Afterwards some considerations and personal experiences are shared on implementing constitutive models into numerical simulation. The discussion focuses on the accuracy of numerical simulation and the influencing factors, selection of proper constitutive models and parameters, consideration of spatial variation of soil modulus in deformation calculation, the strain localization and some solutions for fixing the problems caused by displacement discontinuity at soil-structure contacts in numerical simulation.