Influencing factors affecting the numerical simulation of the mechanized tunnel excavation using FEM and FDM techniques

Numerical simulation methods have been widely applied to model the mechanized tunnel excavation for the purpose of prediction of the system behavior. This research mainly focuses on the influencing factors which may affect the simulation results of tunneling in-duced ground movements. Plaxis 3D (FEM) and FLAC 3D (FDM) are utilized to model the mechanized tunneling process by taking into account the most significant components, namely sequential excavation, face support, grouting pressure and lining installation. The differences in simulation approach between these two programs are demonstrated and the corresponding influences on the model responses are investigated as well. The soil behavior is described by using elasto-plastic Hardening Soil (HS) model which is available in both programs. It is firstly applied to small scale oedometer and triaxial element tests to validate the constitutive model in both programs. This research discusses the discrepancies in the model output due to complex soil structure interactions and intricate mechanized tunneling components subjected to these different simulation techniques. The results show that there is a good agreement between the ground movements predicted by these two programs in case of stiff soil scenario.