TBM Cutter Structure Multi-crack Expansion Mechanism And Life Prediction Method

Tunnel Boring Machine(TBM)is a large integrated tunneling machine,and the cutter disc is the core component of the TBM.Due to the harsh working environment of TBMs,the complex loads they are subjected to can cause varying degrees of damage and cracking to the cutter disc,cutter base,hob and other components,leading to safety problems during the construction process.Therefore,it is of great technical importance to study the mechanism of multi-cracking in TBM cutter discs and to predict the service life of cutter discs in order to extend the life of cutter discs and reduce economic losses in construction.In this paper,the damage characteristics and fatigue life of an actual engineering cutter disc are studied and discussed in depth,with the following main research content:1)Based on the rock breaking test platform of the hob to carry out rock breaking line cutting test,set different pressure to get the three-way load force of the hob line cutting,and carry out simulation of the hob line cutting in ABAQUS to verify the reasonableness of the finite element model;then carry out rock breaking simulation of the central hob,positive hob and side hob according to their working characteristics and digging parameters respectively to get reasonable external excitation of the cutter system.2)In order to obtain the local weak areas of the cutter disc,a static analysis of the cutter disc structure under typical working conditions was carried out to obtain three weak locations.Prefabricated cracks were introduced at the weak locations of the cutter disc,and the crack shape ratio was later changed to obtain the changes in the distribution of the stress intensity factor when the cracks at different locations changed with the shape ratio;the three-dimensional crack expansion method was applied to analyse the changes in the equivalent stress intensity factor when co-linear multi-cracks,parallel multi-cracks and other multi-cracks were distributed on the thin plate,where the change in the angle between the crack and the load had the greatest effect on the stress intensity factor.3)Based on the crack expansion rate model and fracture mechanics knowledge,combined with the Paris formula,the crack expansion of the cutter disc was analysed;the rainflow counting method was used to equate the random load into an eight-level load spectrum,and the finite element software combined with FRANC3 D was used to analyse the crack expansion of the CT specimen,and then the single crack,parallel double crack and co-linear double crack were introduced to the cutter disc sub-model for crack expansion as well as life prediction,after which the influence of the initial crack size,critical crack size and load factor on the life of the cutter disc was analysed,and it was obtained that the initial crack size and load factor had a greater influence on the life of the cutter disc.4)Taking the Northwest Liaoning water supply project as an example,crack extension analysis and life prediction of the cutter disc were carried out to verify the validity of the method in this paper;the collection and statistics of the cutter disc failure data were used to verify the reasonableness of the introduced crack location,and the improvement plan of the crack stop bar was proposed to provide reference for extending the cutter disc life and the cutter disc crack maintenance strategy.