大断面异形盾构同步注浆两阶段复合扩散机制及压力时空分布模式

With the development of section forms, the special-shaped shield is increasingly applied in metro tunnel construction. Due to its geometric characteristics, the unconventional tail void and complex flow path make it more difficult to control the grouting. In addition, the long-term assembly process also makes the grout pressure distribution more difficult to be identified. Based on the analysis of motion characteristics of the grouting diffusion mechanism considering the non-predetermined filling trajectory, viscosity time-varying and displacement / infiltration effect, a compound diffusion model of filling and penetration was established, and the theoretical calculation formulas of grout pressure and space-time diffusion distance were derived. In this study, two stages of grout filling and penetration diffusion in the grouting process were unified, and the transmission and dissipation process of grout pressure were integrated. Based on the example of a quasi-rectangular shield project, the 3D space-time distribution law of grout pressure along the segment was obtained. The results shows that the pressure transmission and dissipation have a significant influence on the total and unit area segment stress. The calculation results in the filling stage show a trend of small up and large down, and gravity dominates. The vertical gradient is about 16 kPa / m, the pressure curve is fuller, and the pressure groove is not obvious. The results of penetration / dissipation under the formation and parameter conditions show nonlinear variation characteristics. The early stage is faster, and the late stage is slower, and the stabilization time is shorter. The impermeable layer makes the difference between the final grout pressure and hydrostatic pressure reach about 46% of the initial penetration pressure. This two-stage diffusion model is closer to the field-measured results. The local trend, fluctuation characteristics and dissipation law are significantly different from the results calculated by traditional methods. It can better explain the movement mode of the slurry in the irregular space and the loss details in its outward diffusion. The research results can also be used in the construction of traditional circular shield tunnels and provide a theoretical basis for the detailed analysis of the stress mode of lining segments in the construction stage.