Experimental study on the diffusion characteristics of polyurethane grout in a fracture

Abstract Although polyurethane grouting has been widely used in fractured rock masses, the understanding of polyurethane diffusion characteristics still needs to be enhanced significantly. To analyse the diffusion mechanism of the polyurethane grout in the fracture, physical simulation experiments were conducted using a self-designed device. Additionally, the influence of grouting quantity on the grout diffusion distance and pressure distribution was investigated. The results indicated that the diffusion radius and pressure field increased with the increase in grouting quantity. Furthermore, the pressure growth rate and grout diffusion rate during the early self-expansion stage is directly proportional to the amount of polyurethane grout injected. However, the change in grout pressure is not synchronised with that of the diffusion radius. Hence, a hysteresis effect was observed for the pressure field change. Additionally, the grout pressure, which was not distributed evenly, decreased along the diffusion radius as it moved away from the grout hole. Furthermore, we derived the relationship between maximum diffusion radius and grouting quantity. Therefore, this study provides a better understanding of the diffusion law of polyurethane grouting in fractured rock masses.