Optimum spacing of TBM disc cutters: A numerical simulation using the three-dimensional dynamic fracturing method

A series of numerical experiments was performed to simulate rock fragmentation by TBM disc cutter. We used AUTODYN-3D to simulate three-dimensional dynamic failure observed in linear cutting machine (LCM) tests. By acquiring the mean rolling force and the mass of rock debris during the numerical test, we were able to calculate the specific energy which is defined as energy required to cut through a unit volume of rock. Before performing the main simulations to determine the optimum cutter spacing, we considered the effects of cutter speed and model size on variation of specific energy. LCM tests were performed numerically on models representing eight different types of Korean rocks. The results were then compared with the results of LCM tests. For isotropic and homogeneous rocks, the optimum cutter spacing deduced from numerical simulations is in good agreement with those determined from LCM tests. The simulations not only provided a realistic description of the rock fragmentation mechanism, but also yielded quantitatively reliable values of specific energy. The results of this study show that the numerical simulations by AUTODYN-3D could possibly be substituted for LCM tests used for performance assessment of TBM.