Research On Static-Dynamic Mechanical Properties And Constitutive Model For The Material Of High Rockfill Dams

The research on the mechanical properties and constitutive model for the material of high rockfill dams is one of the hot topics in geotechnical engineering.Based on the basis of existing research results,the engineering mechanics characteristics and constitutive model of the rockfill material under the static and dynamic loading are studied,from the four aspects of material tests,physical mechanism,mathematical modeling and engineering application,the main research results are as follows:1.A series of experimental study are carried out on static deformation characteristics of the rockfill material under the three different stress paths,such as conventional triaxial tests,p = constant tests and equal stress ratio tests.The strength characteristics,compression characteristics,shear characteristics,stress and strain,particle breakage,critical state and dilatancy properties are discussed.2.A series of experimental study also are carried out on the dynamic deformation characteristics of the rockfill material in the constant amplitude cyclic loading and irregular cyclic loading,such as conventional triaxial cyclic loading tests,deviatoric stress cyclic loading tests and spheric stress cyclic loading tests.It analyzes that the law of development of volumetric strain and deviatoric strain and its deformation mechanism under the different stress conditions,the mechanical properties of the particle breakage and dilatancy properties under the cyclic loading also are discussed.3.The advantages and disadvantages of the existing residual deformation models are analyzed,and the residual deformation model is improved based on the analysis of the residual deformation test results.the following characteristics are mainly included:(1)the calculation of shear strain by the relationship between axial strain and volume strain is adopted,and the influence of poisson's ratio on the shear strain is considered.(2)The development laws of the residual shear strain and residual volume strain of the rockfill material are described in the form of exponential function.(3)The average stress and stress ratio of the initial stress state are used in the residual volume strain and residual shear strain formula to reflect the influence of confining pressure and consolidation ratio on the residual deformation characteristics.4.Based on the understanding of the deformation law under the static and dynamic loading,it is obtained that the particle breakage characteristics of the rockfill material under the action of compression and shear.By introducing the related parameters in the compression breakage and shear breakage,under the framework of eight components proposed by Zhang based on the cyclic deformation law of sands,some reasonable definitions of the existing constitutive models are used,absorbing the advantages of the boundary surface theory and the critical state theory,and a unified constitutive model is developed considering the particle breakage and state.The constitutive model has the following characteristics:(1)The particle breakage characteristics of the rockfill material are considered in terms of compression and shear.(2)By introducing the state parameter,a set of parameters is used for the unified description under different porosity ratio and stress state.(3)The model can describe the deformation characteristics under the monotonic and cyclic loading respectively.5.The Zipingpu CFRD is as the research object,the static analysis of the E-B model,the dynamic response analysis using the equivalent linear viscoelastic model,and the residual deformation analysis of the improved residual deformation model were used respectively,it analyzes that law of acceleration response and residual deformation characteristic of the water level in the wenchuan earthquake,compare with the measured seismic deformation,and preliminarily verifies the validity of the modified residual deformation model.