The Numerical Simulations Of Forces Acting On TBM Disc Cutters With The Consideration Of Confining Pressure And Damage In Rocks

In the constructions of tunnels and undergrounds, the full-face rock tunnel boring machine (TBM) has the characteristics of high degree of automation, security, efficiency and continuous operation in long tunnels, and it represents the contemporary direction of tunneling technology. In the tunneling process of the TBM, the disc cutter is the primary rock cutting tool, which is subjected to severe cutting loads, so the disc cutter is the important part and the main wearing part of the TBM, whose performance directly affects the work performance and efficiency of the TBM and the progress of tunnel excavation. Therefore, the study of the mechanism of the rock fragmenting process by disc cutters and the cutting forces on disc cutters has great significance in the prediction of excavation performance of the entire TBM. However, at present the interaction between disc cutters and the rocks and the mechanism of the rock fragmenting process by disc cutters are still not very clear, and the formula of calculating cutting forces which can fully take into account various factors has not yet established so far. In this thesis, the process of rock cutting by disc cutters and the calculation of cutting force are studied by the numerical simulations, which would provide some beneficial information for the research of the mechanism of the rock fragmenting process by disc cutters and for the determination of cutting forces.In this thesis, the current research status of rock breaking by disc cutters, the empirical formula for predicting forces acting on disc cutters and the current development of the numerical simulation about this issue are summarized firstly. On this basis, it is put forward that numerical simulations in this thesis should be able to consider confining pressure and damage in rocks.Then the explicit dynamic finite element analysis program LS-DYNA is employed to simulate the process of rock cutting by disc cutters. In the LS-DYNA material library, Johnson-Holmquist concrete model, being able to consider both confining pressure and damage in rocks and convenient in parameter determination, is selected to be the material model for rocks in these numerical simulations of this study. In this thesis, the most important work is the numerical simulations and results analysis, which are implemented based on the aforementioned finite element model and material model. By changing the parameter of the numerical simulation model, the influences on the cutting force acting on disc cutters by the cutting depth, the confining pressure, the strength of rocks, the wear of disc cutter, the material damage parameter of rocks, the distance of disc cutters were studied respectively. The conclusions obtained from a series of numerical simulations above showed that the numerical simulation models established in this thesis are reasonable, and the results of the numerical simulations provide certain valuable information for predicting cutting forces acting on disc cutters.Finally, the further research issues in the future were proposed on the basis of the summary of this thesis.