Shu, Pei-YunPei-YunShuChen, Yi-FanYi-FanChenTAI-TIEN WANGHsiung, Bin-Chen BensonBin-Chen BensonHsiungLiao, Chen-YuanChen-YuanLiaoYU-NING GE2026-02-092026-02-092026-0309603182https://www.scopus.com/record/display.uri?eid=2-s2.0-105026751412&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/735892This study numerically investigates the wear degradation of tooth-type cutter bits in shield tunneling through gravel formations, focusing on the effects of gravel content on particle extrusion and friction-related wear mechanisms. The Particle Flow Code 3D (PFC3D) was used to simulate the tooth-type cutter bits of a shield machine excavating in different particle size combinations of gravel specimens. The design of experiments (DOE) was used for the factor configuration with gravel contents (GC) ranging from 30 to 100%, and the statistical analysis of variance (ANOVA) was used to determine the significant microscopic factors of various cutter bit wear assessment criteria. Simulation results showed that the wear trend of the cutter bits assessed using the energy consumption of friction wear criterion was consistent with the results of the physical model tests, with the most severe wear occurring at gravel content (GC) = 60–75% and energy consumption ranging from 19.20–20.66 J under an advance rate of 10 mm per revolution. A regression model was established accordingly, after the microscopic parameters describing the mechanical properties of gravel formation at the site were calibrated, to assess the effect of large particle content of gravel on cutter bit wear with a coefficient of determination exceeding 0.8. Furthermore, simulation results reveal how various sizes and shapes of gravel affect the wear of tooth-type cutter bits at the particle scale. During gravel excavation, soft rounded matrix particles are broken, pushed, removed, and dropped, with a slight increase in the force on the tooth-type cutter bits; however, the irregular large particle clumps surrounded by large particles, which may push each other before breaking the bond, may be quickly ejected after breaking the bond, or owing to the interlocking effect may remain in the gravel to be pushed for a significant distance, and then fall together with larger particles, causing cutter bit force changes that are quite large. Finally, this study makes good use of DOE and PFC3D for simulations and wear assessment processes of cutter bits excavating gravel, enabling quantitative prediction of wear degradation with limited required simulations, and providing a reference framework for wear prediction of cutter bits, associated cutter design, and management for tunnel excavation using shield machines in gravel formations.falseGravel formationPFC3D simulationShield machine excavationTooth-type cutter bit wearjournal article10.1007/s10706-025-03593-22-s2.0-105026751412