UNIVERSAL VISCOELASTOPLASTIC COMBINATION MODEL AND ITS ENGINEERING APPLICATIONS

It is important to select proper model to simulate rheological characteristic of rock in practical engineering.However,most of numerical software including some business programs used widely only have several classic rheological models,which is not enough for identification of models of complicated rock material and will affect development of recognition of rheological constitutive model to some extent.To solve this problem,a universal viscoelastoplastic combination model is proposed.Firstly,the equivalence of generalized Maxwell body and generalized Burgers body is proven.The former is composed of n parallel Maxwell components and the latter is constituted by one Maxwell component and n-1 Kelvin components in series.And the necessary conditions of equivalence for viscoelastic models are also proposed.Secondly,the process of translation from generalized Burgers model to other combined models,which is based on viscoelastic principle of equivalence,is described by cutting down or adding elastic component or visco-component.The universality of generalized Burgers model is verified and universal viscoelastoplastic model is suggested.Then equations of finite difference for universal viscoelastoplastic model are deducted,and the codes of the constitutive equations are written in C++ language based on FLAC3D.The new model,which is required for different rock materials,can be chosen automatically by the codes through the information of model that is input by user.So much complex and trivial work can be avoided.Lastly,the equivalent characteristic of the viscoelastic models is illustrated on basis of creep data of Fuchsia claystone;and the universal viscoelasto-plastic model based on FLAC3D is verified by comparison with inner model of FLAC.A new way to recognizing rheological constitutive models is provided and identification of rheological models becomes possible in global space.