Numerical investigation on grout spread in three-dimensional intersected rock fractures with flowing water

Groundwater inflow through fractured rock masses commonly threatens the safety and stability of underground engineering, and grouting is widely employed to seal fractures. However, grout propagation is influenced by fracture branches under flowing-water conditions in interconnected fractures. Therefore, understanding the flow characteristics of grout in three-dimensional intersecting fractures is essential for effective grouting. To investigate grout spread in intersected fractures, a numerical two-phase grouting model is developed based on the level set method and the Herschel-Bulkley (H-B) rheological model. The proposed model is validated against simulation results and grouting tests in intersected fractures. Then, a systematic analysis is conducted on the sensitivity of grout spread behaviour to the contact ratio of the fracture, grouting pressure, water flow velocity, and grout rheology. The results indicate that larger fracture apertures facilitate more rapid grout accumulation over short periods, promoting the formation of a coherent grout mass within the horizontal fracture. As the contact ratio of the fracture increased, grout spread from the horizontal to the vertical fracture is significantly suppressed. Additionally, flowing water promotes detachment at the grout front, inducing scouring instability and fragmenting the grout interface to evolve into isolated patches. A higher consistency coefficient effectively suppresses instabilities by damping interfacial velocity perturbations. The results provide valuable insights for accurately predicting grout penetration zones and optimising grouting strategies in fractured rock mass.