A semi‐elliptical surface compound diffusion model for synchronous grouting filling stage in specially shaped shield tunnelling

Abstract

In constructing super-large section shield tunnels, it is difficult to guarantee the filling efficiency and uniformity of grouting behind the segments. Studies on grout diffusion models often simplify the grout filling process, leading to inaccurate results, especially for shield tail void with special noncircular profiles. This paper presents a theoretical study on the grout filling diffusion mechanism and its mechanical behaviour, with a particular focus on the grout actual motion process at the synchronous grouting filling stage when the shield is advancing. A semi-elliptical surface compound diffusion model without the predetermined flowing passage was developed, and this model was used to derive the grout filling pressure and diffusion distance formulas. To address the time-varying diffusion surface and irregular integral region issues in derived equations, a stepwise solution algorithm based on the spatiotemporal discretisation operation was proposed. Finally, the grout pressure distribution patterns and some critical influence factors were analysed using a case study in the soft silty clay area to compare the presence and absence of circumferential-longitudinal correlations in the grout filling diffusion process. The results show that the diffusion mechanical behaviour and force transmission significantly affected the total and per-unitarea grout pressures, and the proposed theoretical model is more consistent with the field-measured data. The local trend and fluctuation characteristics of grout filling pressure are clearly different from those of a circular tunnel. The grout filling diffusion mechanism was determined to be the main cause of pressure distribution changes under the premise of a certain initial grouting pressure.

Pressure Model Study on Synchronous Grouting in Shield Tunnels Considering the Temporal Variation in Grout Viscosity

“…Therefore, the grout pressure formation and dissipation are considered two consecutive processes. To establish the theoretical model of the grout pressure during synchronous grouting in shield tunnels, the following assumptions are made [32,33].…”

“…Combining Equation (32) with the boundary conditions (R s = R 0 and P r = P r0 ), the radial grout pressure dissipation can be expressed as follows:…”

Research on the Pressure Distribution Law of Synchronous Grouting in Shield Tunnels and the Force on Segments

“…Qiu (2015) researched the process of the circular filling of the synchronous grouting of a shield tail with slurry, established a mechanical model of the grouting pressure, and analyzed the impacts of factors such as the shield tail gap on the distribution pattern of the slurry pressure [19]. Li Peinan et al (2020) analyzed the diffusion mode mechanism of synchronous grouting in shield tunnels based on the Bingham fluid constitutive model and fluid mechanics principles and established a theoretical model of the longitudinal circumferential diffusion of synchronous grouting at the shield tail [20]. On the basis of existing research, Ye Fei et al (2023) established a grouting compaction splitting diffusion model for shield tunnel walls in low-permeability strata by calculating the distribution of circumferential slurry pressure and the initial splitting pressure in shield tunnels [21].…”

Numerical investigation of slurry property effect on grouting and blocking of flowing water in rock fractures

“…In order to avoid sealing failure caused by the unidentified underground situation, the grouting process in engineering practice usually adopts redundant design to ensure the predetermined slurry diffusion range or water reduction effect. 6,7 This conservative scheme not only causes the waste of grouting materials and potential pollution risk of groundwater resources, but also is not conducive to ensuring the quality of the project. For example, in the grouting treatment of water inflow disaster in a metro tunnel, increasing the final grouting pressure could improve the spread range of slurry but also might lead to tunnel deformation and lining damage.…”

“…At present, grouting is still an empirical technology. In order to avoid sealing failure caused by the unidentified underground situation, the grouting process in engineering practice usually adopts redundant design to ensure the predetermined slurry diffusion range or water reduction effect 6,7 . This conservative scheme not only causes the waste of grouting materials and potential pollution risk of groundwater resources, but also is not conducive to ensuring the quality of the project.…”