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The grouting method is commonly used to seal rock fissures in subsea tunnels, and therefore the water and mud inrush can be prevented in this way. However, the current understanding of the grout diffusion mechanism inside the rock fissure under seawater conditions is still limited, especially inside the inclined rock fissure. This study first presented a novel rock fissure geometry schematization, which can be simplified to a single fissure with different inclinations. Then, based on the obtained time-varying grout viscosity under seawater conditions, the grout diffusion model of cement and sodium silicate grout (C-S grout) was developed by combining the equilibrium equation, constitutive equation, and continuity equation, which can be used to calculate the key parameters involved in rock fissure grouting, i.e., the grouting pressure and grout diffusion distance. After that, the change of grouting pressure with time was obtained. Furthermore, the numerical simulation of grouting in the inclined rock fissure was performed to verify the suitability of the grout diffusion model, and the comparison between them shows that they match reasonably well with each other. It is hoped that the conclusions could aid in the design of grouting in rock fissures around subsea tunnels with C-S grout in the future. HIGHLIGHTS: A novel rock fissure geometry schematization is presented. The C-S grout diffusion model in the inclined rock fissure under seawater is developed. The effect of time-varying viscosity on grout diffusion under seawater conditions is studied. The relation between the grouting pressure and grout diffusion distance is obtained. The numerical simulation of grouting in the inclined rock fissure is performed. [ABSTRACT FROM AUTHOR]

Grouting is one of the main technical means to prevent water inrush hazards in coal seam floor aquifers. It is of great significance to elucidate the diffusion law of slurry in the process of grouting in fractured aquifers for safe mining in coal mines. In this paper, the mechanism of slurry diffusion in horizontal fractures of fractured aquifers was studied based on the Bingham slurry with time-varying characteristics; additionally, a one-dimensional seepage grouting theoretical model considering the temporal and spatial variation of slurry viscosity under constant grouting rate was established. In this model, the grouting pressure required by the predetermined slurry diffusion radius can be obtained by knowing the grouting hole pressure and injection flow. Slurry properties, fracture parameters, grouting parameters, and water pressure were the parameters affecting the slurry diffusion process. Looking at the problem of water disaster prevention of coal seam floor in the Working Face 2509 of the Chensilou Coal Mine, according to the aquifer parameters and model calculation results, a grouting scheme with a slurry diffusion radius of 20 m and grouting pressure of 12 MPa was proposed. Finally, with the comparative analysis of the transient electromagnetic method (TEM) and water inflow before and after grouting, it was verified that the design grouting pressure and the spacing of grouting holes were reasonable and the grouting effect was good. [ABSTRACT FROM AUTHOR]

To get an accurate bearing capacity of a postgrouting pile, the range of grout diffusion should be considered in practice. Considering the time-dependent behavior of power-law cement grout viscosity, calculation methods are proposed to determine the diffusion radius and the climbing height of the grout. Moreover, an iterative calculation method is established to compute the climbing height of the grout along a single pile embedded in layered soils. Four cases reported in the literature are used to demonstrate the effectiveness and accuracy of the proposed calculation methods. The calculation results show that the computed grout diffusion radius and climbing height of the grout are in good agreement with the measured value. For practical purposes, to get an accurate prediction on the bearing capacity of postgrouting pile, the time-dependent behavior of grout viscosity should be considered. [ABSTRACT FROM AUTHOR]