Dynamic viscoelastic model for rock joints under compressive loading

The mechanical properties of rock masses are significantly affected by the deformated behaviors of discontinuities, such as joints and faults. Rock masses in nature are also often subjected to dynamic disturbances, including explosive and seismic loads. Therefore, it is crucial to understand the deformed response of rock joints under dynamic loads. In this study, a series of dynamic compression expriments are carried out on rock joints with different joint roughness using the SHPB equipment with digital image correlation (DIC) technique. It found the dynamic compressive bebaviors of rock joints have viscoelstic features. Then a variable-order fractional Kelvin-Voigt (VFKV) model is proposed to simulate this behaviour, which consists of a variable-order fractional viscous dashpot and a spring in parallel. The model is verified to effectively represent the dynamic compressive process of rock joints. Finally, based the proposed model, the influence of model parameters, loading rate, and joint contact area ratio on the viscoelastic behaviour and mechanical property of rock joints are discussed. The results show the viscoelasticity behaviour of joints is significantly affected by the loading rate and joint contact area ratio, high loading rate and joint contact area may strengthen the elastic properties of the joints, while the joint roughness has the opposite effect. •The dynamic viscoelastic behaviours of rock joints under compressive loading are observed and analysed by digital image correlation technique.•A dynamic viscoelastic model for rock joints under compressive loading is proposed based on the variable-order fractional theory.•The effects of loading rate and joint contact area ratio on the viscoelastic behaviour of rock joints are studied.