A Unified Hardening Constitutive Model For Structured Soil Considering Bonding Play

Natural soils are exposed to the natural environment for a long time,and bonding are formed between particles under the action of various physicochemical factors,and the presence of bonding significantly affects the stress-strain relationship of the soil material.Although the initial strength of bonding structured soils is high when they are loaded,once the soil starts to yield and break down,it is often sudden and unsuspected,which is very unfavorable for practical engineering.Therefore,in order to analyze the bonding structured soil engineering problems,it is necessary to establish a unified hardening constitutive model for structured soil considering bonding play.In this paper,based on the unified hardening constitutive model of structured soil,the concepts of bonding stress and reference bonding stress are introduced to establish a unified hardening constitutive model of structured soil that can consider bonding play,derive its stress-strain relationship equation in the p-q stress space,and extend it to the three-dimensional stress space by the transformation stress method based on the SMP criterion.By analyzing the evolution law of the constitutive model,the presented constitutive model can continuously and smoothly describe:(a)The effects of the degree of structuredness on the stress-strain relationship of the bonding structured soil in isotropic consolidation tests.(b)The effect of bonding play on the stress-strain relationship of the bonding structured soil in conventional triaxial shear tests.(c)The effect of stress Lode angle on the stress-strain relationship of the bonding structured soil in true triaxial shear tests.The predictions for 12 soils,including Ningbo clay,Shanghai clay and Nanjing clay,show that the presented constitutive model can reasonably describe the physical and mechanical behaviors of various bonding structured soils in isotropic consolidation tests,conventional triaxial shear tests and true triaxial shear tests.The user material subroutine of the model was written and embedded into Abaqus finite element software,simulations of the unit soil and foundation soil were carried out to verify the reasonableness and validity of the presented model.