Effects of slurry and rock type on shear properties of grout-filled jointed rock: Experimental and numerical investigation

This study investigates the influence of slurry type and rock type on the evolution of microscopic failure during the shear process of grout-filled jointed rock (GJR) through direct shear tests and nanoindentation experiments. The interfacial shear fracture behavior is analyzed, and an interfacial bond strength model is established. Results indicate that the variation trend of shear strength is consistent across all specimen types. Mudstone specimens grouted with a self-developed high-performance composite cement slurry (MH) exhibit the most pronounced reinforcement effect and the smallest interfacial transition zone (ITZ). Additionally, a discrete element method (DEM) model is proposed and validated to investigate the shear performance and progressive failure mechanisms. Numerical simulations confirm that tensile cracks dominate the failure process, with micro-cracks formed before peak stress accounting for 10% to 30% of the total. Furthermore, coordination number distribution and acoustic emission (AE) analyses reveal that the MH specimens display a higher proportion of shear failure modes compared to other specimens. Finally, energy evolution within the GJR specimens during shear loading is examined. Variations in slurry type result in greater dissipative energy losses compared to variations in rock type. The MH specimens demonstrate the highest proportion of damping energy and require greater elastic energy for failure initiation, indicating superior interfacial bonding performance. This work provides a novel perspective for optimizing material selection and enhancing grouting effectiveness in the reinforcement of fractured surrounding rock masses.