Stress And Deformation Analysis Of CFRD Based On The Hypoplastic Constitutive Model Of Rockfill

Rockfill materials are an important engineering material,which are the main component of the concrete faced rockfill dam,Meanwhile,the rockfill bears most of the load.The stress and deformation characteristics of rockfill has great influence on the safety of the CFRD.The research progress of the constitutive model of rockfill materials and the basic theory of hypoplastic model are presented,what's more,the Gudehus-Bauer model described the mechanical properties of sand material is introduced.Then,the Gudehus-Bauer hypoplastic constitutive model and the determination of its parameters are studied.Finally,the Gudehus-Bauer model is improved for rockfill,which is used to analyze the stress and deformation of the CFRD.The specific research can be summarized as follows:(1)The basic concept of hypoplasticity is briefly introduced.Then,the tensor operation rules and the general form of the hypoplastic constitutive model are expounded.Compared with the elastoplastic model,the mechanical properties of the Gudehus-Bauer model are revealed.(2)The confined compression test curve is adopted to determine the hypoplastic constitutive model parameters h,and n for rockfill materials.According to the derivation of the model equation for the parameters a and ?,the relationships between the parameters and the confining pressure are established,What's more,the new fitting parameters are proposed for the parameters.(3)Taking into account the obvious dilatancy for rockfill materials,the new volume strain term is added to the linear term of the Gudehus-Bauer hypoplastic constitutive model in order to improve the axial strain-volumetric stain curve calculated by the model in the triaxial consolidated drained tests.The new model parameters and the amelioration of the Gudehus-Bauer hypoplastic constitutive model are proved by means of the confined compression tests,the triaxial consolidated drained tests and the loading-unloading simulation.(4)Considering the rotation of the main stress during the storage period of the concrete faced rockfill dam,a scalar factor ?1 of the middle principal stress parameter is introduced.In addition,the modulus matrix of the improved Gudehus-Bauer hypoplastic constitutive model is deduced in detail and the expressions of the components are also provided.Besides,the incremental method for solving nonlinear equations is introduced,and the modification of the corresponding variable increment direction is added in the mid point incremental method for the hypoplastic constitutive model.(5)The finite element program of the improved Gudehus-Bauer model is developed in order to calculate the stress and deformation of the CFRD.Compared with the Duncan Chang E-B model and the ShenZhuJiang double yield surface model,the improved Gudehus-Bauer hypoplastic model can be applied in the analysis of the stress and deformation of the CFRD.