Abstract: Due to the presence of bedded or jointed planes, layered rock mass shows transversely isotropic characteristics in mechanics. Therefore, the existing isotropic creep model is difficult to fully reflect the creep constitutive model of transversely isotropic rock mass. In order to obtain the three-dimensional transversely isotropic creep constitutive model, the Burgers model is adopted to describe the characteristics of instantaneous strain, decaying creep and steady creep of transversely isotropic rock mass. Based on the assumption of constant Poisson’s ratio and three-dimensional isotropic creep constitutive equation, a three-dimensional creep constitutive equation of transversely isotropic rock mass is derived through differential operator method by substitution of transversely isotropic compliance matrix into isotropic compliance matrix. The new model also takes the differences of creep behaviours between specimens with horizontally and vertically oriented bedding into account. According to the characteristics of creep constitutive equation, a method for identifying the creep parameters in the three-dimensional creep constitutive model is proposed based on the creep test results. The model is applied to the identification of triaxial creep test parameters, and a comprehensive set of three-dimensional creep parameters are obtained. The rationality of the proposed creep equation is verified by comparing theoretical values with experiment results. The limitations of the traditional creep tests design scheme are further pointed out and some suggestions for creep tests design of transversely isotropic materials are given. The research results provide a new insight for the study of three-dimensional creep mechanism of rock mass and provide scientific support for the design of rock mass creep tests.

Key words: transversely isotropic, three dimensional model, creep equation, parameter identification