Dynamic Characteristics Analysis Of An Open TBM Gripping-thrusting-regripping Mechanism

TBM(Tunnel Boring Machine)is widely used in the major infrastructure construction such as rail transit.The GTRM(Gripping-Thrusting-Regripping Mechanism)is the core drive mechanism for continuous,efficient and precise tunneling of TBM.However,due to the harsh geological environment and strong impact load,the vibration of the mechanism is especially severe during the operation,which may lead to a series of engineering problems such as damage of key components,wear of hinges,cracking of welds,abnormal operation of hydraulic equipment,and it’s seriously affect tunneling efficiency and construction safety of the whole machine.Based on the above engineering background,the dynamic modeling and dynamic characteristic analysis of the open TBM’s GTRM are studied in this paper with a goal to provide an important technical foundation for the design and construction of such mechanism.The main works are as follows:In the aspect of topological structure analysis,the composition and working principle of TBM’s GTRM are systematically analyzed,and the number and type of DOF(Degrees Of Freedom)of the mechanism are determined.According to the topological characteristics of the mechanism,the design criteria of mechanism topological structure satisfying the requirements of tunneling operation under complex geological conditions are summarized.The above work lays the foundation for the dynamic modeling,dynamic characteristic analysis,structural and dimension parameter design of the mechanism.In the aspect of dynamic modeling,based on composition and stiffness topological relationship among the components of TBM’s GTRM,the dynamic model of the mechanism is established by using the centralized parameter method,which takes into account the factors such as the clearance between shield and surrounding rock,the stiffness of the driving system,the stiffness of the moving pair,the stiffness of the surrounding rock,the damping,the actual rock breaking load,etc.In the model,the DOF of mechanism translation at horizontal direction,vertical direction and tunneling direction,and the DOF of mechanism torsion around horizontal axis,vertical axis and tunnel central axis are considered.In the aspect of natural characteristic analysis,based on the above dynamic model,the natural characteristics of GTRM and its variation with parameters are studied.The first four natural frequencies and their corresponding vibration modes of the mechanism in a certain pose are obtained by numerical simulation.The variation of the natural frequency with the parameters is revealed,and it’s reflect that the stiffness of hydraulic cylinder is the main factor affecting the low-order natural frequency of mechanism,and there are many modal transitions in the process of natural frequency changing with stiffness.The nature of the above phenomenon is revealed preliminarily,and the specific location of mode transition point is given.In the aspect of dynamic response analysis,the responses within the clearance of GTRM are simulated by using the Runge-Kutta method.Then,the influences of the clearance,stiffness of driving cylinder and speed of cutter head on the responses are analyzed by RMS(Root Mean Square).The research results show that the clearance has significant influence on the translational vibration at the horizontal direction and rotational vibrations around both vertical and tunnel axis.In addition,increasing the stiffness of the cylinder is an effective way to reduce the vibration amplitude,and the stiffness of the cylinder can be increased by adjusting its oil pressure during operation,so as to achieve the purpose of suppressing the vibration of the mechanism.