Assessment of slurry chamber clogging alleviation during ultra-large-diameter slurry tunnel boring machine tunneling in hard-rock using computational fluid dynamics-discrete element method: A case study

To fundamentally alleviate the excavation chamber clogging during slurry tunnel boring machine (TBM) advancing in hard rock, large-diameter short screw conveyor was adopted to slurry TBM of Qingdao Jiaozhou Bay Second Undersea Tunnel. To evaluate the discharging performance of short screw conveyor in different cases, the full-scale transient slurry-rock two-phase model for a short screw conveyor actively discharging rocks was established using computational fluid dynamics-discrete element method (CFD-DEM) coupling approach. In the fluid domain of coupling model, the sliding mesh technology was utilized to describe the rotations of the atmospheric composite cutterhead and the short screw conveyor. In the particle domain of coupling model, the dynamic particle factories were established to produce rock particles with the rotation of the cutterhead. And the accuracy and reliability of the CFD-DEM simulation results were validated via the field test and model test. Furthermore, a comprehensive parameter analysis was conducted to examine the effects of TBM operating parameters, the geometric design of screw conveyor and the size of rocks on the discharging performance of short screw conveyor. Accordingly, a reasonable rotational speed of screw conveyor was suggested and applied to Jiaozhou Bay Second Undersea Tunnel project. The findings in this paper could provide valuable references for addressing the excavation chamber clogging during ultra-large-diameter slurry TBM tunneling in hard rock for similar future.