Study On Disc Cutter Mechancal Behavior And Optimization Of Cutter Head Layout In Combined TBM Tunneling In Chongqing Rock Area

In recent years,rocky layers like those in Chongqing and Qingdao are often met in urban rail transit construction.The composite TBM fully combines the advantages of rock tunnel boring machines and shield machines,and is gradually applied in Chongqing rail transit construction with its characteristics of high efficiency,high speed,high security,environmental protection and high quality.With the gradual maturity of technology application,the composite TBM will play an increasingly important role in the construction of urban rail transit construction in rock layers.Compared with engineering practice,theoretical research on composite TBM is relative lag.Especially when it comes to the rock breaking mechanism,its mechanical interaction with surrounding rock,the cutter abrasion estimation,the cutter head force condition and cutter optimization layout of composite TBM under rock layers,there is no unified understanding on these technical problems.Based on Chongqing Rail Transit Link(Nanqiao Temple ~ Sports Park ~ Yanjiaba),this paper focuses on mechanical interaction between surrounding rock and cutters,the layout and wear estimation of cutters,the mechanical properties of cutter head and the improvement of cutters in geological high risk section with the program ‘analysis on mechanical behavior and parameter optimization of composite TBM in Chongqing core district'.Five methods,such as data research,laboratory test,theoretical analysis,numerical simulation and field experiment,are used together to study the cutter rotary cutting rock laboratory test,wear and service life of cutters,cutter-and-rock interaction model,the improved layout of cutter structure and mechanical properties of cutters in geological high risk section.The main contents are as follows:1.The 2.28 m cutter machine is used as integrated test-bed to develop the cutter rotary cutting rock laboratory test,with high precision controller to collect and control test data and high speed camera to observe the whole process of rock breaking.This paper studies the optimal knife spacing,cutter layout,optimal penetration and excavation parameters.By sieving the size and weighing the weight of the rock ballast,the specific energy consumption is discussed,and the parameters of cutters are determined.Also in this paper,the assemble angle of cutters is further adjusted,and the mechanical properties of the cutters in the transition zone of the edge cutter are studied.The mechanical differences between the edge cutter and inner cutter are proved.2.In order to accurately simulate the mechanism and relationship between the abrasion of rock-breaking and cutters,the model cutter with a scale of 1:10 is used according to the configuration of the cutter size,and the cutter abrasion test machine is used to carry out the cutter wear test.Further,through the rock abrasion test,the relationship between the abrasive value of the rock and the amount of cutter wear is established.By comparing and analyzing the influence of cutter excavation parameters and blade width on the cutter wear under different rock samples as well as the influence of rock breaking environment on cutter abrasion,the TBM tool wear prediction model is finally established to provide support for tool design,construction cost and tunneling parameter prediction.3.Based on the three-dimensional particle discrete element method,the particle flow calibration experiment is carried out on the typical sandstone in Chongqing.The differences of the mechanical properties of cutters and the crack propagation range under different models such as cutter intrusive rock breaking,rolling rock breaking and comprehensive rock breaking are analyzed.The shortcomings of the traditional cutter rock breaking model are discussed.The particle flow mechanics model of the interaction between the cutter and the surrounding rock considering the actual motion behavior of the cutter is established,which more accurately expresses the rock breaking behavior.4.Based on the mechanical properties of cutters,the wear of cutter,the mechanical properties of the cutter head and the rock crack propagation,the optimization design of the composite TBM cutter head is studied.Starting from the central cutter,the inner cutter and the edge cutter,the layout of the composite TBM cutter head is optimized from three aspects: the cutter pitch,the cutter installation phase angle and the cutter installation inclination.Taking the composite TBM used in the construction of Chongqing Rail Transit Loop(Nanqiao Temple ~ Sports Park)as an example,the optimal design scheme is given.5.Based on the three-dimensional granular flow cutter rock breaking model,the mechanical properties of the cutters and the crack propagation of the rock during TBM excavation under complex layers and high ground stress are analyzed and corresponding improvement measures are proposed.Also,this paper provides a theoretical basis for the optimal layout of the cutter head when the composite TBM is constructed under similar geological conditions.