Penetration mechanism of grouting by using the cement-based slurry with time-dependent viscosity

The fracture grouting method can play a very good anti-seepage and reinforcement effect for some rock layer that are not compacted or have hidden dangers such as leakage channels, soft layers, cracks, and so on. However, the mechanism of action requires further in-depth study. In this study, to investigate the penetration of time-dependent viscosity of the slurry in the surrounding rock, cement-based slurry was used as the object of research to carry out the time-dependent viscosity tests, analyze its rheological characteristics, and determine its time-dependent viscosity. Based on the Bingham model of slurry, a grout diffusion model was established, considering into consideration slurry time-dependent viscosity and the rock type I fracture toughness. In addition, this study considered the impact of rock aperture deformation on the grout process, established a grout penetration equation, and explored the influencing factors of the slurry penetration range. The process of grouting’s strengthening of the fractured rock mass is addressed from both macroscopic and microscopic perspectives, and the correctness of the grouting penetration formula is confirmed by comparing in-situ grouting borehole endoscopic pictures in the coal mine tunnel. This study demonstrates that the grouting penetration radius increases very slowly after the grouting pressure reaches a certain level, but it is easier for the slurry to combine with the coal rock body to form a tightly consolidated body under high pressure. Therefore, the grouting pressure should be designed based on the rock media type and engineering disturbance. The results of this study could give a theoretical foundation for the selection and design of parameters required for grouting engineering practice.