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Achieving highly efficient extrication of the tunnel boring machine (TBM) cutter-head driving system from the collapsed surrounding rock has become a key problem globally, and significant effort has been directed to improve TBM cutter-head extricating ability. In this study, the characteristics of a hydro-viscous device have been investigated to improve extricating performance of the TBM cutter-head. A numerical method based on an explicit pressure-linked equation is presented for computing the film parameters of the HVC, which is then applied to investigate extrication characteristics of a TBM cutter-head with a hydro-viscous clutch (HVC). The explicit pressure-linked equation is derived from the Navier–Stokes equations and the conservation equation, where boundary conditions are involved. The model of a cutter-head driving system with an HVC is established, and the extrication characteristics of the cutter-head driving system are analyzed and compared with three extrication strategies. The variation in extrication torque shows that the linear strategy or positive parabolic strategy are preferred for their relatively high extrication efficiency and low rigid impact, and the effects of throughflow rate on torque transmission are also investigated. The test rig of the TBM cutter-head driving system was set up to validate the numerical method and the model of a cutter-head driving system, and the feasibility of the proposed numerical method for researching the extrication of the TBM cutter-head is verified.

This paper presents a new cutter-head driving system of tunnel boring machine (TBM) with hydro-viscous clutch (HVC) applied in order to improve the extricating performance, and a kind of theoretical methodology is proposed to analyze the extricating performance of HVC. Firstly, the Navier-Stokes equations are reduced upon the characteristics of oil film within HVC and the dynamical mathematical models of cutter-head system in the process of extrication are established. Then an approximate iteration algorithm is adopted to solve the NS equations and the analytical expression of the HVC output torque is obtained. Therefore the real-time simulation for the extricating process is performed. The theoretical results are validated in an experimental rig containing one friction pair. It is confirmed that the theoretical methodology is valid for the good agreement between the theoretical and experimental results. The results reveal that the HVC can indeed improve extricating performance of TBM cutter-head especially in relieving rigid impact. Furthermore, this also provides a design idea for the rotating speed regulating system especially in large mechatronics equipment when the hydro-viscous clutch is applied.

This article proposes to apply wet clutches to the cutter-head driving system of tunneling boring machine TBM and also investigates the soft-starting transmission characteristics of the wet clutch under three different strategies. The strategies discussed here refer to the engagement rules of plates in wet clutches, and they are: positive parabola, straight line, negative parabola. The numerical simulations corresponding to those strategies are carried out in the FLUENT, and the result indicates that the numerical method is valid for the good agreement with the analytical one. After comparing the simulation results, we conclude that the positive parabolic engagement strategy can be preferred during the soft-starting of TBM cutter-head if the invalid starting time, starting smoothness and heat dissipation are regarded as the evaluation standard.