A viscoplastic Cosserat peridynamics and the simulation of creep failure of geomaterials

In this study, within the framework of Cosserat peridynamics, the viscoplastic Perzyna’s model and the modified Drucker-Prager criterion are introduced to investigate the creep failure of geomaterials. The biaxial compressive creep for soft rock and the uniaxial creep for sandstone with a prefabricated flaw are designed to verify the proposed model. The effects of lateral pressure, internal friction angle, and cohesion on creep failure are investigated. Results show that the three stages of creep and the corresponding damage patterns are successfully predicted, which accords with the observations of numerical and experimental results. The larger lateral pressure makes it harder for geomaterials to creep. Geomaterials with a larger internal friction angle or cohesion have stronger shear resistance and less plastic deformation, making them less susceptible to creep failure. Besides, the Cosserat internal length l_c affects the inclination angles of the shear band.