UDEC Modelling on Dynamic Response of Rock Masses with Joint Stiffness Weakening Attributed to Particle Crushing of Granular Fillings

Characterization on the response of the jointed rock mass to the stress wave is of great significance for rock engineering and the prevention of dynamic geological disasters. A joint in the rock mass produces discontinuous deformation under dynamic loads and can be weakened on both stiffness and strength, which further affect stress wave propagation in a feedback manner. However, previous numerical models mainly used the linearly elastic model (LEM) (constant stiffness) and the nonlinear Bandis-Barton model (BBM) (compression-strengthening stiffness) to characterize the dynamic response of the rock mass which neglected dynamic damage and stiffness weakening of the joint. To overcome this problem, we adopted a modified BBM (MBBM) to establish an advanced numerical model of the dynamic response of the rock mass by the Universal Distinct Element Code (UDEC). The MBBM is capable of characterizing joint stiffness weakening attributed to the filled particle crushing, which can be also degraded into both LEM and BBM. Our model was well verified by experimental data on stress wave propagation through an artificial filled joint. Dynamic responses of rock masses containing a single joint, a set of parallel joints, and intersected joints were systematically investigated considering the amplitude and incident angle of the incident wave as well as the joint spacing. Results showed that weakening of the joint stiffness had an important impact on the wave transmission and effect of multiple reflections at joints. Compared with previous models, our model has prominent advantages and accuracy in simulating dynamic damage and weakening response of the rock mass.