Abstract：By comparison of Burgers model with visco-elastoplastic model，this paper considers visco- elastoplastic model is adaptive to all kinds of rock rheological characteristics，while Burgers model is only suitable to rather soft rock. Due to taking the relationship between s and ss into account，constitutive equations of visco-elastoplastic model are presented by segmented functions. When s ＜ss in the visco-elastoplastic model，creep never causes infinite deformation and relaxation wouldn′t result in stress disappearing. When s ≥ss，deformation caused by creeping will last all along，but stress caused by relaxation never decreases to zero. The Burgers model，regardless of relationship between s and ss，holds deformation to infinite as long as s is not equal to zero，which is contradictory to the rheological characteristics of rock. Moreover，according to triaxial creep test of rock samples，authors fit the curve of -t of the gray-yellow miliolite from fault of Zhaogezhuang Coal Mine respectively by visco-elastoplastic model and Burgers model and obtain their rheological parameters by least squares procedure. The fitting results show that the visco-elastoplastic model is more suitable than the Burgers model to describe rock rheological characteristics.
