Geomechanics

Numerical Simulation of Rock-Cutting Mechanism of Tunnel Boring Machine

Accurate estimation of acting forces on the disk cutter is very important in the design of Tunnel Boring Machines (TBM) operations factors such as propulsion (driving) force and torque. To do this, first the forces applied to a single disk cutter, as well as its performance for a particular rock, are determined by performing a linear cutting machine (LCM) test. The results are then generalized for design of TBM on the same rock. In the present numerical study, the linear cutting machine test for a fixed cross-sectional cutter was simulated using LS-DYNA software, and the results of the numerical model were compared with the laboratory results. The results show that the use of the Lagrangian solution method is not appropriate due to the strong dependence of the accuracy of the results on the failure criterion defined to remove the elements, and the use of the SPG solution method will be a more appropriate option instead. Also, using the RHT material model instead of the JHC model will have a much better estimate of the width of the damaged area in the rock. The accuracy of the results shows that in the next step, this solution method can be used to simulate the rotational cutting machine (RCM) test.

Calibration of Six Constitutive Material Models for Geomaterial

Recently, several constitutive material models have been developed and added to the LS-DYNA library to predict concrete geomaterial behavior. These developments were established merely from using concrete compressive strength, which limits the level of robustness in capturing actual concrete behavior. This study focuses on developing a simplified approach to calibrate six constitutive material models including Soil and Foam, Pseudo Tensor, Geological Cap Model, Concrete Damage Model Rel-3, Johnson Holmquist, and Continues Surface Cap Model against Triaxial and Hydrostatic Compression Tests (TXC and HCT) data. Comparisons between individual numerical results were performed to evaluate whether accuracy can be offered through a corresponding constitutive material model. The presented calibration method can also be applied to different geomaterials such as rock and soil.