Dynamic Analysis And Vibration Control Of Tunnel Boring Machines(TBM)

Hard rock tunnel boring machines(TBM) is a mechanical equipment used for tunnel excavation, having been widely applied to railway, highway, water conservancy and civil infrastructure in recent decades. The mechanical structure of TBM thrust system consists of a cutterhead, a main beam, a back support, a saddle, a support hydraulic cylinder and two grippers. Rock penetration and tunnel excavation are carried out with TBM cutterhead rotation. Meanwhile, tunnel supporting and slag are realizing, thus making the full-face of the tunnel formed in one step. Intensive vibration of TBM thrust system is excited by rock breakage loads, which leads to the inefficiency in construction. In order to estimate the vibration characteristics of TBM thrust system, vibration test was done in a tunnel excavation field, and dynamic analysis was made for a TBM model theoretically. The results of the test show the intensive vibration of the TBM in excavation process. The vibration of main beam is coupled by multiple DOFs, and the vibration power mainly focuses in low-frequency band. In the dynamic analysis, the thrust, gripping, guide constraint are considered and the stiffness of hydraulic cylinders and joints are introduced. The equivalent stiffness model were established of guides sliding, gripper gripping and shield supporting. And TBM dynamic model was assembled through the displacement method and the vector operation. Vibration analysis results of TBM system show that the natural frequency of the longitudinal vibration of main beam decreases with the decreasing stiffness of thrust cylinder. The first three frequencies are very close to each other. And the vibration is coupled. These results are consistent with the measurement results and important for vibration suppression design in TBM thrust system.In order to suppress the vibration of TBM thrust system, a approach using dynamic vibration absorber(DVA) is considered based on the results of measurement and analysis. However, to ensure the vibration reduction effectiveness, the mass needed is very large for the traditional DVA, which is not suitable for TBM because of the limited available space for DVA installation. In this work, a new DVA based on the leverage principle is therefore proposed with the mass amplification effect. The dynamics equation describing the motion of the mass-spring system with this new DVA is developed, and the frequency response function is obtained. Furthermore, the stiffness and damping of the proposed DVA are optimized using fixed-point design theory. Finally, the dynamics model of TBM-DVA system was established and the frequency response function is obtained. By means of GA-SPQ method, the parameters of this new DVA were optimized using different objective functions. The performances of the optimized DVA and that of the non-optimized DVA are compared. The results show that this new DVA is effective in the vibration suppression for TBM thrust system.