Theoretical considerations of field penetration index model and its application in TBM performance prediction

Abstract Field penetration index (FPI) is a representative key indicator for tunnel boring machine (TBM) performance estimation, however its application in real tunneling projects still limited because of the lack some theoretical knowledge on relationships between FPI, rock mass properties, and TBM specifications. This study aims to establish FPI model by analyzing tool–rock interaction disc cutters from perspective. was first done comparison cutter with that polycrystalline diamond compact (PDC) bit, which indicated they share similar breakage mechanisms force equilibrium. A series cutting tests were then conducted granite, marble, limestone determine relationship rotary torque applied thrust during cutting. Referring test results features PDC bit cutter, derived verified using field dataset. It found linearly correlated but independent rotation speed In addition specifications’ contribution, parameters abrasiveness purely control this linear relationship. The proved shows strong positive properties (uniaxial compressive strength integrity), even under different drilling conditions, providing basis empirical establishment. Therefore, practical engineering, it recommended use multi-parameter classification system values—such as structure rating (RSR), (RMR), quality index(Q)—instead individual —such uniaxial strength, or update semiempirical models.