Tunnel Boring Machine (TBM) Cutter Spacing Design Based on Simulations of Rock Breaking Process Using a FEM-SPH Coupling Method

Abstract

AbstractFor the finite element method (FEM) simulation of rock cutting by tunnel boring machine (TBM) cutters, there exists a problem that the rock beneath the cutter tip is over-broken while the rock beside the cutter tip is under-broken, and thus the evolution and force transfer of the dense core is difficult to simulate. Aiming at this problem, the three-dimensional rotary rock cutting model including two TBM disc cutters is built using an FEM-SPH (smooth particle hydrodynamics) coupling numerical method. The Mohr-Coulomb elastoplastic constitutive model based on tensile truncation is selected, and the critical transformation threshold of FEM meshes to SPH particles is determined by simulating the uniaxial compression and the Brazilian splitting processes. The numerical model is verified by full-scale excavation tests carried out by a TBM cutterhead. Based on the numerical simulations, the influences of cutter spacing on rock fragmentation process, normal force, rolling force, and specific energy are studied. The results show that the macroscopic physical phenomenon of dense core evolution, side crack propagation, and rock chip splashing can be well simulated; the errors between the numerical and experimental average normal force and rolling force are lower than 10%, verifying the reliability of the numerical model; the rock cutting specific energy decreases first and then increases with the increasing of the cutter spacing in between 60 and 110 mm, and the optimal cutter spacing is determined as 83 mm.KeywordsTunnel boring machineRock breaking by disc cutterFinite element methodSmooth particle hydrodynamics