Experimental study on sealing effect of cement–sodium silicate slurry in rock fracture with flowing seawater

Cement–sodium silicate (C–S) slurry has been widely used to prevent water inrush during the construction of submarine tunnels. The diffusion mechanism of C–S slurry in seawater is still unknown. In this study, a series of contrast and orthogonal tests was conducted using a visual fracture grouting device to investigate the effects of the initial flowing water speed, seawater content, grouting rate, roughness, and aperture width of rock fractures on the propagation patterns and sealing effect. The contrast test results showed that seawater has a significant impact on slurry diffusion and fracture sealing. The orthogonal test results indicated that the propagation patterns can be classified into four types according to the experimental results: (1) complete sealing without cavities or water flow channels; (2) incomplete sealing with large cavities but no water flow channels; (3) partial sealing with water flow channels along both sides of the fracture; and (4) failed sealing with obvious water flow channels composed of many cavities. The descending order of factors on the sealing effect was as follows: initial water flow speed, seawater content, aperture width, roughness, and grouting rate. Moreover, the influences of these factors on the sealing effect were revealed. The sealing effect increased with the seawater content and grouting rate, and decreased with the initial flowing water speed, roughness, and aperture width. The results contribute to the understanding of the grouting diffusion mechanism and the design of grouting treatments for water inrush in submarine tunnels to reduce the risk of tunnelling.