Numerical investigation of TBM disc cutter cutting on microwave-treated basalt with an unrelieved model

Cutter wear or damage is a significant issue during tunnel boring machine (TBM) tunneling in hard rock. Microwave preconditioning has been verified as a promising approach to reduce cutter wear and enhance the TBM excavation efficiency. Thus, understanding the TBM cutting performance for microwave-treated hard rock is necessary. First, numerical verification of a cutting model was performed to examine the universality and reliability of the model. Then, the rock mechanical parameters of microwave-treated basalt were calibrated using linear Mohr-Coulomb theory. Finally, linear cutting simulations were conducted with an unrelieved rock model by considering the variables of the disc cutter penetration depth and microwave irradiation conditions. The numerical results indicated that the maximum reduction in the rolling and normal forces reached 38.38% and 44.95% (under a 5-kW microwave power and 3-mm penetration depth), respectively. A novel indicator of the linear friction energy was proposed to assess disc cutter wear, and the maximum reduction reached 36.81% under a microwave power of 5 kW and penetration depth of 4 mm. Considering the microwave weakening efficiency, TBM tunneling efficiency and cutter wear, microwave parameters including a high microwave power and short irradiation time were suggested for future practice.