Numerical simulation of rock breaking by TBM disc cutter in soil-rock composite formations

During tunnel boring machine (TBM) construction, the rock breaking effect of the disc cutter in complex formations affects the progress and cost of the entire project. Therefore, it is necessary to better understand the rock breaking mechanism of TBM in complex formations. In this study, matrix discrete element method (MatDEM) software is used to study the rock breaking mechanism of the disc cutter at the interface of soil and rock. Based on the theoretical study and analysis of rock breaking process of the disc cutter in the soil-rock composite formations, the three-dimensional dynamic rock breaking process of the disc cutter in soil-rock formations with different rock dip angles (0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees) is simulated by using MatDEM, and the simulation results are analyzed from three aspects: the unit force, the fracture number of unit connection, and the system energy. The main conclusions are as follows: when the disc cutter is used to roll and break the rock at the soil-rock interface of composite formations, the unit force and the fracture number of unit connection are positively related to the contact area S of the rock and blade at the front edge of the disc cutter. The energy to break the rock by the disc cutter is mainly affected by the broken rock volume per unit time Vdt. The greater the Vdt is, the more energy the disc cutter needs to break the rock is. The total force P is affected by the contact area S (beta, t). The change of the maximum total force is small when beta = 15 degrees, 30 degrees, and 45 degrees, and is obviously lower at 60 degrees and 75 degrees, respectively.