Assessment on the reverse circulation performance of slurry shield pipeline system assisted with CFD-DEM modeling under sandy cobble stratum

Reverse circulation of slurry shield pipeline system is one of the most effective method to solve slurry chamber clogging during shield tunneling in cobble stratum. In this paper, the assessment on reverse circulation performance of slurry shield pipeline system was performed using the computational fluid dynamics-discrete element (CFD-DEM) coupling approach. In the CFD-DEM coupling model, the shape and size of large irregular cobble particles were considered via 3D scanning technology. In addition, a parametric analysis was conducted, and the effects of the cutterhead rotational speed, slurry inlet velocity and rheological properties of slurry on the reverse circulation performance were investigated respectively. The results indicate that, the magnitude of impact on reverse circulation is in the order of slurry inlet velocity v > slurry plastic viscosity k > cutterhead rotational speed r > slurry yield stress τ0 > slurry power law index n among the working parameters of slurry shield and the Herschel-Bulkley (HB) rheological parameters of the slurry, and the time of reverse circulation is also of importance to the performance of the reverse circulation. Accordingly, a reasonable reverse circulation scheme was suggested, and applied to practical engineering. The findings in this study could provide some references for slurry shield pipeline system reverse circulation of similar projects in the future.