Study on the creep characteristic and model of overgrown joint rock

A step incremental-circular loading and unloading method was used, and a set of creep experiment was done to study the creep characteristic of weak and intricate rock with overgrown joint. The testing data were managed according to the retrievable instantaneous elastic strain and lagged viscoelastic strain, and the in-retrievable instantaneous plastic strain and viscoplastic strain. And the essential rules of visco-elasto-plastic characteristic of the weak and intricate rock are obtained. Based on scientific analysis and compared study, Burgers creep model was united with Mohr-Coulomb criterion and a modified Burgers-creep model was formed. The new model is characterized by a visco-elasto-plastic deviatoric behavior and elastoplastic volumetric behavior. The viscoelastic and viscoplastic strain-rate components are assumed to act in series. And some programs about the modified Burgers model were developed to deal with the testing data. The creep characteristic curves were obtained, and the model parameters were fitted and the values were gotten through weighted mean. The testing results show that the creep testing curves are coincident well with the theoretic curves, which validates the modified Burgers-creep model is felicitous to characterize the creep of the kind of rock.