Assessing cutter-rock interaction during TBM tunnelling in granite: Large-scale standing rotary cutting tests and 3D DEM simulations

Abstract

The widespread utilisation of tunnel boring machines (TBMs) in underground construction engineering requires a detailed investigation of the cutter-rock interaction. In this paper, we conduct a series of large-scale standing rotary cutting tests on granite in conjunction with high-fidelity numerical simulations based on a particle-type discrete element method (DEM) to explore the effects of key cutting parameters on the TBM cutter performance and the distribution of cutter-rock contact stresses. The assessment results of cutter performance obtained from the cutting tests and numerical simulations reveal similar dependencies on the key cutting parameters. More specifically, the normal and rolling forces exhibit a positive correlation with penetration but are slightly influenced by the cutting radius. In contrast, the side force decreases as the cutting radius increases. Additionally, the side force shows a positive relationship with the penetration for smaller cutting radii but tends to become negative as the cutting radius increases. The cutter's relative effectiveness in rock breaking is significantly impacted by the penetration but shows little dependency on the cutting radius. Consequently, an optimal penetration is identified, leading to a low boreability index and specific energy. A combined Hertz-Weibull function is developed to fit the cutter-rock contact stress distribution obtained in DEM simulations, whereby an improved CSM (Colorado School of Mines) model is proposed by replacing the original monotonic cutting force distribution with this combined Hertz-Weibull model. The proposed model outperforms the original CSM model as demonstrated by a comparison of the estimated cutting forces with those from the tests/simulations. The findings from this work that advance our understanding of TBM cutter performance have important implications for improving the efficiency and reliability of TBM tunnelling in granite.