Abstract: As a main research object in underground engineering, rock has obvious rheological properties due to its material composition and complicated geological environment. Applying Burgers constitutive model (which is formed with a series of Kelvin model and Maxwell model) to particle flow code in three dimensions (PFC3D), this research analyzes the impact of different parameters (including elastic coefficients Em and Ek, viscosity coefficients ?m and ?k, and friction factor f ) on the instantaneous and rheological properties. The controlling variable method is used. Conclusions can be drawn as follows. The instantaneous strength properties are mainly affected by Maxwell’s elastic coefficient Em and friction factor f . The elastic modulus and uniaxial compression strength have positive correlation with Em and f . However, Poisson’s ratio is positively correlated with Em and negatively correlated with f. Meanwhile negative correlations are observed among rheological properties and these parameters. Based on these conclusions, a staged increment loading creep experiment of red shale is simulated. Comparisons with results from laboratory experiments prove the feasibility of Burgers constitutive model in PFC3D for creep experiments. At the same time, this method is used in staged increment cyclic loading and unloading experiment and triaxial creep experiment. This research is also a new attempt to analyze creep properties of rock material with discrete element method.

Key words: soft rock, compression creep tests, particle flow code, Burgers model, parameter analysis, rheological properties, discrete element method