Analysis of TBM disc cutter performance based on the pressure distribution to optimize operational efficiency

The excavation mechanism of Tunnel Boring Machine (TBM) cutter discs in rock tunnelling is highly complex. Because an extremely high contact pressure develops at the disc–rock interface, it triggers fractures in the rock and leads to chip formation. This study develops two predictive models that relate specific energy ( S E ) consumption in rock cutting to both the spacing-to-penetration ( s / p ) ratio and uniaxial compressive strength ( U C S ). The first model extends the Colorado School of Mines (CSM) framework by replacing its single contact-pressure distribution with alternative profiles, thereby revealing how the pressure profile governs the orientation and magnitude of disc-induced forces across different rock types. The second model is fully numerical. It uses contact-pressure profiles recorded in the laboratory with specialized testing machines (LCM and ILCM) for several rock types at reference penetrations, then generalizes these profiles across the full penetration range and computes the resulting cutting forces. The results are presented as characteristic curves that relate the S E to the s / p ratio and the U C S . The study shows that asymmetric and narrower profiles contribute to increased prediction uncertainty. The optimal s / p ratio is roughly 13–14 for low-strength rocks, drops to just under 10 for medium-strength rocks, and rises slightly above 10 for very high-strength rocks. A broader experimental pressure distribution profile better captures variations in contact pressure, enabling more stable and accurate predictions. Based on the performed analyses, knowledge of the contact pressure distribution is essential for identifying the optimal s / p ratio, which is associated with the minimum Excavation Specific Energy. This will thereby enable the proper design of the TBM cutter head and the effective management of the machine during tunnel advancement.