Research On The Design Method Of Symmetrical And Non-uniform Layout Of Shield Propulsion System Under The Coupling Of Multi-directional Loads

Shield machine,as a modern large-scale engineering equipment which can make the tunnel form once,plays an extremely important role in the construction of metro tunnels to alleviate the urban ground traffic pressure.However,due to the imperfect design theory of shield propulsion system in China,unbalanced loads occur during the tunneling process and the segment is damaged,which affects the waterproof performance of the tunnel and greatly reduces the service life of the tunnel.Therefore,the research on the design theory of the propulsion system is the focus of the current shield field.In this paper,the anti-eccentric load characteristics of the shield propulsion system are studied in depth.The existing shield propulsion system is composed of more than ten or dozens of hydraulic cylinders with equal spacing.Because of the uniform layout of the propulsion system,it is not enough to solve the problem of segment rupture caused by excessive eccentric load.In this paper,a design method of non-uniform layout propulsion system based on relative force coefficient is proposed.The adaptability of non-uniform layout system based on relative force coefficient in composite stratum,the implementation method of non-uniform propulsion system and the stress of segments under different layout systems is studied in detail.Specific research contents are as follows:Firstly,the stress of shield propulsion system during tunneling is analyzed in detail.The analysis shows that under the coupling action of external tunneling resistance,horizontal resistance torque and longitudinal resistance torque,the hydraulic cylinder in the propulsion system will produce non-uniform thrust to overcome external resistance,which will lea d to eccentric load of the propulsion system.Secondly,according to the geological parameters and shield body parameters,a symmetrical and non-uniform layout scheme of propulsion system in composite strata is proposed.In order to get the layout parameters of the hydraulic cylinder,based on the mechanical model of the propulsion system,a symmetrical solution model is proposed,and the ADAMS simulation analysis shows that the propulsion system with the layout design method has better force transfer characteristics,which can effectively transfer the external load to the tunnel segment uniformly.Then,in order to reduce the eccentric load of the propulsion system,a planar four-bar mechanism is designed to adjust the position of the hydraulic cylinder in the circumference of the propulsion system.Considering the limitation of the workspace,the main space of shield machine and the ultimate strength of the segment,the comprehensive size of the regulating mechanism is designed.Under given stratum conditions,the force transfer performance of the propulsion system with adjus Tab.layout capability is verified by CV offset load evaluation index and virtual prototype.The results show that the adjusted non-uniform thrust system has better force transfer performance than the uniform thrust system.Finally,through a simulation experiment,it is verified that the non-uniform propulsion system has good anti-eccentric load characteristics in composite strata.This paper mainly uses Solidworks Simulation finite element method to analyze the stress of tunnel segment.Considering the influence of uniform system and symmetrical non-uniform system on the stress of segment in composite stratum,it is found that the deformation of segment is the most under symmetrical non-uniform layout by analyzing the deformation cloud and stress cloud.Small,the force is the most uniform.