Dynamic crack propagation behavior of high-strength mortar-granite specimens with different inclined interfaces

High-strength mortar is widely employed in the reinforcement of fractured rock masses due to its exceptional strength, durability, and bonding performance. Under dynamic loading, the crack propagation behavior in high-strength mortar–rock composites is complex, with potential for cracks to extend along the interface or penetrate through it. While considerable research has focused on static interfacial fractures, the mechanisms driving penetration propagation under dynamic loading remain relatively underexplored. To address this gap, granite was chosen as the reinforcement target and combined with high-strength mortar to create side-cracked triangular plate (SMCT) specimens. Impact tests were conducted using a modified split Hopkinson pressure bar (SHPB) system. During the tests, an infrared velocimeter measured the impact velocity, while strain gauges and a super-dynamic strain gauge were utilized to collect waveform data. By integrating experimental and numerical methods alongside crack propagation gauges (CPGs), the effects of interface inclination, roughness, and mortar strength on crack propagation parameters, dynamic fracture toughness, and fracture energy were systematically investigated. A numerical model was developed using ABAQUS software, incorporating embedded zero-thickness two-dimensional four-node cohesive elements (COH2D4) to simulate random crack propagation. Crack propagation velocity and time were derived from experimental data, and the dynamic stress intensity factor and dynamic fracture toughness were calculated using a universal function. The results indicate that as the interface inclination increases from 90° to 106°, the average fracture toughness in the mortar and granite regions rises by 19% and 23%, respectively, while the average fracture energy increases by 38% and 56%, respectively. Moreover, when the compressive strength of the mortar increases from 80 MPa to 100 MPa, the average initiation toughness of the specimen improves by 32%. Roughness does not significantly affect penetration crack propagation velocity, dynamic fracture toughness, or fracture energy. Numerical simulations reveal that under impact loading, the tensile stress at the crack tip is significantly greater than the shear stress, which approaches zero, indicating that the SMCT specimens consistently exhibit mode I fracture characteristics.