Rock Chip Properties of TBM Penetration in Jointed Rock Masses Based on an Improved DICE2D Simulation

In most cases, TBM tunnels are constructed in jointed rock masses. Rock chip properties can be used to interpret the response of the rock mass to the TBM tunnelling. Engineering-scale simulations can help us to explain the relationship between rock chip properties and rock mass conditions. In this study, a GPU-based DICE2D programme is presented to meet the computation requirements of the engineering-scale simulation. The smooth joint model (SJM) was also incorporated into DICE2D via an improved joint side checking approach. Using the SJM-embedded DICE2D, a multiple-cutter penetration model was set up. The combined influence of joint spacing and angle on the rock breaking process and rock chip properties were analysed. Further, a rock chip extraction algorithm was proposed to quantify the shape and size distribution. The results showed that in the rock masses with the close joint spacing, the smaller the alpha angle, the blockier the rock chips were. As the joint spacing increase, the rock chips become flat. Both the joint spacing and alpha angle affected the size distribution. The overall size of rock chips decreased with the increasing joint spacing, and first increased with the increasing alpha angle and then decreased when the alpha angle was over 60°. The very closely jointed rock mass at the alpha angle of 90° was an exception because rock slabs would be produced. In addition, in the jointed rock mass with the joint spacing less than 250 mm and 60°–75° alpha angle, or in the highly jointed rock masses with 90° alpha angle, significant differences between the forces acting on the different cutters were revealed.