Research On Structural Design Method For Cutterhead Driving System Of TBM

With various functions and complex structures,full-face hard rock tunnel boring machine(TBM)is a modern large tunnel construction equipment,which can reflect the ability of a national equipment manufacturing.As the working load is huge,the main bearing and cutterhead bolt in driving system have low reliabilities.Once one of them failed,the construction cost would be increased,maintenance or replacement cycle would take lots of time,and construction efficiency would be reduced.The structure connected to the main bearing has multiple interfaces with other structures and mechanisms,while there is no clear design criterion or method to guide the design currently.The function and form of the structure are considered in design,but the guidance of the load transfer path,which will affect the performance of the main bearing,is ignored.Hence,the study of the relationship between the stiffness and the load transfer characteristics,to improve the design quality and guarantee the effectiveness of TBM,is of great theoretic value and practical significance.In this paper,the transmission structure of cutterhead driving system in open style TBM is taken as an example,to research and analysis the influence of structural stiffness on the performances of key component,and the main contents are shown as follow:(1)The load characteristics of driving system structure and the influencing factors are analyzed.The load of driving system structure has quadratic moment obviously,which caused by stiffness characteristics of the cutterhead,and the load characteristics have been verified by experiment according to the principle and similarity of the minimum potential energy.Considering the law of the influence of boundary constraint on the load characteristics of transmission structure,a simulation method of boundary stiffness based on the cutter's load model of the Colorado Institute of Mines(CSM)is proposed,which provides the basis for the study of forced state and performance of the main bearing.(2)The influence of the characteristic parameters of driving system structure on the forced state of the main bearing is studied.With the constraint of the configuration and size of the transmission structure,the influence of the adapter flange equivalent length,the mounting style of the main bearing and the cross-section of the front beam on the quadratic moment of the distributed load are analyzed.The design direction of the structure is provided to improve the forced state of the main bearing.(3)The load distribution of the main bearing thrust raceway and its influence on the main bearing performances are analyzed,and a method of estimating the life of the main bearing based on the slice method and the excavation load statistic is proposed.The load distribution of the main bearing is calculated by the finite element method to consider the influence of the structural coupling stiffness.According to the characteristics of the load distribution,the safety factor and the rated life of the main bearing are checked.Based on the frequency distribution of the measured excavation load,the method of estimating the service life of the main bearing based on Miner's cumulative damage theory is proposed by combining the slicing method.The influence of the characteristic parameters of the driving system structure on the performances of the main bearing is analyzed,which provide the foundations for the structure design and the performances check.(4)The relationships between the stiffness characteristic of driving system structure and the stress and its variation of the dangerous point of cutterhead bolt are obtained by using the multi-level modeling method.The reason of the connection slip between the transmission structure and the cutterhead is analyzed theoretically and experimentally,and its influence on the dangerous point stress of the bolt,that is,the position of the first bearing.Based on the load distribution model of the main bearing,the relationship between the tension force and end displacement of the bolt and the stiffness of driving system structure is obtained by using the multi-level modeling method,which provides the basis for the design and assembly of driving system structure to improve the reliability of system.