Study on diffusion mechanism of different cement slurry in simulated plate fracture

Grouting diffusion mechanism of fractured strata in seawater is pivotal for submarine tunnel safety. In this study, ordinary Portland cement (OPC) and sulphoaluminate cement (SAC) slurries were tested for diffusion in fracture under seawater hydrostatic and hydrodynamic conditions. The results showed slurries diffused circularly within hydrostatic fracture, circular, oval, and U-shaped stages were found in hydrodynamic conditions. OPC had longer diffusion distance and lower test pressure. Compared with smooth fractures, diffusion time in rough fractures of OPC increased by 20.5%, while that of SAC rose by 13.3%. Diffusion distance against water in rough fracture was greater than that in smooth fracture. Numerical results confirmed the accuracy of diffusion patterns observed in model tests. Pressure variation had two stages: growth and stable periods. Pressure distribution was primarily influenced by fracture width. Pressure loss in rough fracture was higher than that in smooth fracture, and the pressure loss in hydrodynamic water (18.52–31.09%) was slightly greater than that in hydrostatic water (4.82–26.56%). Meanwhile, final diffusion pressure in hydrodynamic water (591–14546 Pa) was slightly greater than that in hydrostatic water (465–13346 Pa). These findings supported the optimisation of grouting design and promoted safer, more efficient submarine tunnel construction.