Dynamic progressive damage evolution and fracture characteristics of layered slate based on a digital rock core

The dynamic damage and fracture behaviour of layered slate is strongly controlled by its bedding structure. To investigate the dynamic failure mechanism, internal bedding information was obtained using CT scanning. Through spatial mapping between the digital rock core and the finite element mesh, bedding elements were accurately identified using a voxel-averaged threshold method, and a three-dimensional numerical model representing the real spatial characteristics of bedding was constructed. Based on this model, SHPB numerical simulations were performed using the Johnson–Holmquist II (JH-2) constitutive model, and the model was validated by experimental results. The results indicate that the pre-peak dynamic response of layered slate exhibits a pronounced bedding-plane-dominated behaviour, which can be divided into an elastic stage, a bedding-dominated plastic stage, and a strengthening stage governed by the cooperative load bearing of the rock matrix and bedding. The dynamic failure mechanism shows a progressive transition from bedding-dominated to crack-dominated behaviour: cracks first initiate at the incident end and adjacent bedding planes due to end tensile failure and bedding weakening, propagate along bedding and introduce geometric defects, and subsequently trigger the initiation and propagation of trans-bedding cracks, forming a composite fracture mode.