The Study Of Elasto-plastic Damage Constitutive Model Of Soil With Cementation Strength

With the application of numerical methods in the field of civil engineering,the constitutive relationship of soil becomes an important research topic.Many constitutive models of soil are built on the basis of remolded soil,while the remolded soil has destroyed the bonding and cementation of soil particles,and its mechanical properties are simple.Many soils in the nature,such as undisturbed soil,improved soil and frozen soil,have a strong cementation structure between the particles in the soil,which is macroscopically reflected as cementation strength of soil,and shows different mechanical properties with remolded soil.The soil in the loading process,inter particle cemented structure was destroyed,the cementation strength of soil is reduced,at the same time,the micro crack expansion for material damage,these have important effects on soil mechanical properties.Therefore,the existing remolded soil model can not reflect the mechanical properties of this kind of structural soil well.In this paper,we focus on influence of two factors,cementation strength and damage,on the mechanical properties of soil.The main work is as follows:1.On the basis of the classical elastoplastic theory of soil,in order to reflect the mechanical characteristics of structured soils,a cementation strength and its revolution rule are imported into Subloading yield and Superloading yield surface model(SYS model)to establish a new constitutive model.Analyzed the influence of parameters(cementation strength,overconsolidation,structure)in the elastoplastic constitutive model under different drainage conditions.We found that cementation strength and overconsolidation have great influence on the mechanical properties.Compared with the triaxial compression tests results of cement-treated soil,the proposed model can describe the compaction,dilation and hardening,softening behaviors well during shear.2.According to the mechanical characteristics of structured soils,cementation strength and damage rule of modulus are imported into Subloading yield and Superloading yield surface model(SYS model),and an elaso-plastic constitutive is proposed based on the continuum damage mechanics,coupling the damage and elastic plastic.Compared with the triaxial compression test result of frozen saline soil,the proposed model can describe the deformation behavior and damage characteristic of frozen soil.3.In this paper,an optimization program based on nonlinear least square method is applied to realize the solution of the optimum parameters of the constitutive model.The influence of parameter range on accuracy is also studied.The results show that the optimization program has high precision and operation speed,and can solve the optimal solution of the model parameters well.