Method for calculating penetration range of grouting slurry in the reinforced tunnel by high-pressure rotary jet grouting from ground

Due to the advantages of good integrity, high strength and low permeability, surrounding rock reinforced by high-pressure rotary jet grouting in shallow buried section of tunnels has been gradually applied to practical engineering. However, the slurry penetration process is closely related to porosity, penetration path and construction parameters, thus it is difficult to determine the slurry penetration range. Through considering the properties of rock and soil, the hydrodynamic characteristics of grouting slurry and penetration path, a plane analysis model of slurry penetration range was established based on cavity expansion theory, and the calculation formula of radial penetration range of high-pressure rotary jet grouting was derived. Its application scope and parameter determination were also analyzed. Comparing with the field excavation, rationality of the theoretical formula was verified. Furthermore, the primary factors affecting the penetration range of slurry were discussed. The results show that the radial range of slurry permeation from theoretical formula and field measurement is 0.63 times and 0.618 times of pile radius, respectively, and the deviation of between theoretical permeation range and measured one is only 2%, which indicates that the proposed formula can well reflect the property of surrounding rock at shallow buried section of tunnels and the effect of construction parameters. The penetration filling range of high-pressure slurry increases with the increase of porosity, slurry water-cement ratio, rotary jet pressure and the decrease of tortuosity. The proposed method can provide theoretical basis for designing pile spacing and pile diameter, and for the evaluation of reinforcement effect on shallow buried section of tunnels using high-pressure rotary jet grouting.