A Study On The Structure Design And Opening Characteristics Of The Shield Cutter Head In The Soft And Hard Interactive Stratum

Shield tunneling machine is the main mechanical equipment in tunnel construction.Its safety and reliability are very important for construction safety and efficiency.The cutter head is the key part of shield machine,which plays the role of excavating and stabilizing the tunnel face,mixing and discharging muck.However,in the current construction process,there are often some problems with cutter head such as blocking,cracking and abnormal tool wear.In order to ensure the safety of shield tunnel construction,different cutter head structure and opening design should be adopted in different strata.Unsuitable cutterhead structure and opening design may cause the cutterhead to crack and wear,which will affect the construction safety and efficiency.This paper provides a systematic theoretical study and numerical simulation analysis for the opening design,static and dynamic performance evaluation of the cutterhead.The research content of this paper includes the following four parts:(1)The cutterhead opening plays a role in discharging the muck from the excavation surface to the soil chamber.In view of the problem that the opening rate of cutterhead can not reflect the actual slag removal effect of the cutterhead opening,this paper proposes a method to replace the opening rate with the opening rate of cutterhead in different partition,and divides the cutterhead into several equal width ring-shaped partition,and calculates the opening rate for each of them to judge whether the opening size of is reasonable or not.The method proposed in this paper can evaluate the actual slag removal effect of the cutterhead more accurately and effectively.(2)In the process of construction,when the natural frequency of cutterhead is close to the external excitation frequency,the cutterhead will resonate,which will lead to cracking of it.In this paper,a set of equipment for monitoring the vibration of shield cutterhead was designed and successfully used in the vibration monitoring in Jinan Metro Project.After the vibration data is collected by the equipment,this paper used Kalman filter algorithm and FFT to process and analyze the vibration data,and obtained the main frequency of cutter head vibration,which provides a reference for avoiding cutter head resonance when designing.(3)The cutterhead cracking is a serious problem for shield machine.In order to study the structural strength of the cutterhead,this paper first collected the data of a shield section project in Jinan metro,and used FEA to simulate and analyze the stress and deformation of the cutterhead under the static force.After three times of welded steel plate reinforcement,the safety coefficient of the cutterhead structure was increased from 1.22 to 1.39.Secondly,this paper analyzes the influence of three structural parameters on the stress and deformation distribution of the cutterhead,which are the angle of the cutterhead bracket,the position of the bracket support and the wall thickness of the bracket.On this basis,the static performance of cutter head can be optimized.(4)The mode of cutterhead is a dynamic characteristic of cutterhead itself.In this paper,the modal analysis of the cutterhead of Jinan metro is carried out.After three times of welded steel plate reinforcement,the rigidity and natural frequency of the cutter head increased continually,and the factors affecting the cutterhead modal are analyzed.The influence rules of the angle of the bracket,the position of the bracket support,the opening rate of the cutter head and the wall thickness of the bracket on the cutterhead modal are obtained.According to this law,the natural frequency of the cutterhead can be changed to prevent the cutterhead from resonating,so as to optimize the dynamic performance of the cutter head.The results of this paper can provide theoretical guidance for the cutterhead designers when arranging the cutter head opening.It can also be used to optimize the structure design of cutterhead,and avoid the resonance and cracking owing to larger local stress and natural frequency close to construction frequency.The research results of this paper can further accelerate the research and development process of domestic shield cutterhead.