Simulation And Analysis Of TBM Gripping-Thrusting-Regripping Mechanism During Tunneling Operation

Tunnel Boring Machine(TBM)is a kind of large-scale tunnel construction equipment that can realize automatic excavation and one-time forming of tunnels.The Gripping-Thrusting-Regripping Mechanism(GTRM)is the core driving mechanism of TBM thrusting system.During tunneling operation,the mechanism vibrates violently under large alternating loads.It is easy to deviate from tunneling track and its parts and components are easy to be damaged.It is necessary to accurately analyze the static and dynamic characteristics of the mechanism.Based on the above engineering background,starting from the motion analysis of GTRM,this thesis studies the static,modal and dynamic finite element(FE)modeling methods of the mechanism,and analyzes its static and dynamic characteristics,so as to provide theoretical basis for TBM design and construction.In the aspect of motion analysis,the structure and working principle of GTRM are introduced at first.Then,the inverse position solution and workspace analysis are carried out under three working conditions of thrusting,regripping and gripping,according to the three strokes of a working cycle.The stroke variation of driving cylinders versus tunnel distance is solved,and the minimum turning radius under the influence of various structural parameters is obtained,which provides the basis for the FE modeling in the following part.In terms of static analysis,a static FE model considering the stiffness of the components,hydraulic oil and joints,the connection between joints and the actual load is established.Based on this,a modeling method which can rapidly build the FE models of the mechanism in various positions is proposed.Taking the parameters of the engineering prototype as an example,two typical load conditions are selected to analyze the force of the driving cylinders and the stress of the parts.The accuracy of the redundant drive cylinder equivalent rod model and the effectiveness of the rapid FE modeling method are verified.The forces of driving cylinders decrease with increasing tunnel distance.Under various loading conditions,the force of the propel cylinder is the same.The larger the vertical torque is,the greater the deduced gravity will be,and the smaller the torque cylinder will bear.The greater the horizontal torque,the greater the stress on the gripping cylinder.In regard to modal characteristic analysis,a modal FE model considering the stiffness of elastic elements and the connection between joints is established.The natural characteristic of the mechanism and its variation versus stiffness parameters are analyzed.The first six natural frequencies and corresponding vibration modes at the middle of tunneling distance are obtained.The natural frequency corresponding to some vibration modes varies obviously versus tunneling distance.The influence of the oil stiffness of propel and torque cylinders and the connection stiffness between the shield and the surrounding rock along all directions on the natural characteristics is obtained,and the weak elements of the vibration along all directions of the mechanism are determined.In relation to dynamic response characteristic analysis,a dynamic FE model considering the stiffness of elastic elements,the connection between joints,driving parameters and the actual load is established,and the dynamic response characteristics of the cutterhead were simulated and analyzed.Considering the force of cutter,the measured load spectrum and the arrangement of cutter on the cutterhead,the load history of the cutterhead is obtained.The displacement response of cutterhead along three directions is obtained when forced vibration occurs within ten seconds from the middle of tunnel distance.The vibration amplitude along the tunneling direction is the largest,followed by the horizontal direction and the vertical direction.