Simulation of dynamic evolution of rock muck migration in full-section shaft boring machine based on DEM

Aiming at the bottleneck of rock muck migration efficiency during construction by full-section shaft boring machines, this study establishes a numerical model based on the discrete element method to systematically investigate the dynamic influence of cutterhead cone angles on muck aggregation processes. Numerical models with varying cone angles (25°, 30°, 35°) were developed, and particle contact parameters were calibrated using field test data to achieve dynamic simulation of the entire muck migration process. The results indicate that when the cutterhead cone angle ≥35°, self-organized migration for rock muk driven by gravity can be achieved, leading to formation of distinct flow channels within 2 s and accumulation of nearly 90% of particles in the central zone by 50 s. At 30°, muck requires scraping forces from the rotating cutterhead are required to converge rock muk toward the center, while a 25° cone angle induces significant particle retention, necessitating auxiliary discharge devices. A complete muck discharge system model further demonstrates that, with the optimized 35° cone angle, a discharge efficiency of over 90% can be achieved, meeting the requirements for super-large-diameter shaft construction. This research provides theoretical guidance for cutterhead structural optimization in shaft boring machines.