An Explicit Finite Element Approach to TBM Disc Cutter-Induced Rock Fragmentation Simulation

In rock tunnelling, tunnel boring machines (TBMs) are extensively used for mechanical rock cutting. A good understanding of the rock fragmentation process and subsequently TBM penetration rate could be very useful in the design and operation of TBMs with better scheduling of the project. The important parameters in the design of a TBM cutter head include the cutting forces, rock material characteristics and the cutter configuration. The main tools employed by TBMs for rock fragmentation are disc cutters. The rock cutting process can be characterized by two approaches, namely physical testing and numerical modelling. Although physical tests have proved to be reliable, they are uneconomical and time-consuming owing to the intrinsic heterogeneity in the rock material. Moreover, physical tests do not provide a detailed explanation of the initial rock fragmentation process. Numerical modelling, on the other hand, provides a detailed insight into all the phases of the rock fragmentation process. However, the numerical methods are mostly based on some assumptions and do not easily take into account random imperfections in rocks. The finite element approach, among the available numerical methods, can be used to analyze the distribution of temperature, stress, strain, and strain rate in the chip generation zone of the rock cutting process. Using explicit finite element algorithm LS-DYNA, a technique for modelling the fragmentation process during mechanical rock cutting is briefly discussed. FEM algorithm explicitly captures the dynamic interactions during TBM rock cutting and the nonlinear features of the rock material.