Vibration Analysis And Life Prediction Of TBM Cutterhead Under Spatially-distributed Loads

As a key piece of equipment in the tunnel construction field, the full face rock tunnel boring machine (TBM) is typical large complex equipment with the complex technology and high additional value, which can reflect the level of a country’s equipment manufacturing industry. Cutterhead is the core component of TBM, and its life is equivalent to the TBM’s life. In the process of excavation, the cutterhead vibration is extremely severe, due to the "three high" surrounding environment of high hardness, high temperature and high quartz content, also with the multi-point impactive rock crushing characteristic of multi-cutters. For this reason, the cutterhead stress state and load transfer law is extremely complex, which leads to severe engineering fault by a large area crack damage before the scheduled life index. The fundamental cause is that the cutterhead system dynamic behavior and damage mechanism under the extreme conditions are hard to forecast, and the cutterhead vibration reduction and damage resistant design under the strong impact environment are also extremely difficult. Hence, the study on TBM cutterhead dynamic characteristics and fatigue life, to put forward the design basis of structure parameters, is of great theoretical value and practical significance. In this paper, a split-cutterhead is taken as an example, to study and analyse the vibration characteristics and fatigue life, and the main works are as follows:1) Multi-degree-of-freedom coupling dynamic behaviors and vibration mechanism of the TBM split-cutterhead system influenced by complicated factors:the spatial multi-point time-varying stochastic excitations, meshing stiffness, clearance as well as bearing stiffness are comprehensively taken into account, and the deformation coordination relationship among components is deduced, to establish a coupling dynamic modle of TBM split-cutterhead system. In addition, a quick decoupling method for the TBM split-cutterhead system based on Newmark-β’s numerical integration method is proposed, and then the influence rules of different complex factors on cutterhead system vibration characteristics are analysed, including the tunneling parameters, cutterhead piece mass, as well as the layout parameter of main driving. Besides, the cutterhead vibration measured acceleration field data is used to correct and validate the accuracy and reliability of the proposed dynamic model.2) A mixed-mode stress intensity factor model of split-cutterhead structure based on the submodeling technique:for the complexities of cutterhead structure and load boundary, the crack stress intensity factor is difficult to be determined. Based on the dynamic loads of cutterhead joint surface and spatial time-varying excitations of multi-cutters, the 8 level equivalent fatigue load spectra are obtained by using rain flow counting method, and the calculation method of mixed-mode stress intensity factor about split-cutterhead structure is proposed, which is validated by the Newman-Raju formula. Then, the influences of crack position angle, shape ratio and depth ratio on stress intensity factors are presented, which can reveal the crack tip dominant propagation rules with different parameters.3) TBM cutterhead crack propagation life prediction and parameters influence under the complicated boundary conditions:based on the equivalent fatigue load spectrum of each level, the mathematical expression of equivalent stress intensity factor at the deepest crack tip in the cutterhead weak position is fitted, to analyse the crack propagation rule of cutterhead. Then, a fatigue crack growth life prediction model is established on the basis of Newman model and cumulative damage theory, so as to predict the cutterhead fatigue life. Moreover, the influence rules of structural parameters, crack size parameters and growth rate parameters on the cutterhead life are analysed, to provide reference for the cutterhead structure design, damage resistance criterion, maintenance strategy and material selection.4) Vibration characteristic and life prediction of the TBM cutterhead in Liaoning Northwest Water Supply Project:to further verify the validity and practicability of the model and method, the cutterhead in Liaoning Northwest Water Supply Project is taken as an example, the system vibration model is established by the proposed method in this paper, to calculate the cutterhead dynamic responses and dynamic loads at the position of cutterhead joint surface, and the cutterhead fatigue life is predicted. Finally, a cutterhead structure improved scheme is proposed.