Modifications to an elasto-visco-plastic constitutive model for prediction of creep deformation of rock samples

摘要

Time-dependent features of rocks and rock masses, particularly soft rocks, may emerge in most tunnels, mines and underground constructions under different deviatoric stress levels. To account for the creep deformation of rocks associated with the wide range of stress levels, modifications are made to a visco-plastic model which was initially developed for large stresses in squeezing conditions. Firstly, the concept of plastic hardening behavior is adopted for both instantaneous and visco-plastic deformations of rocks to estimate the induced plastic deformation even at relatively low deviatoric stress levels. Secondly, the visco-plastic dashpot element is described as a function of the stress level to determine the secondary stage of creep during the unloading and reloading phases which are crucial in tunneling and underground.