Study On Vibration Source Intensity And Prediction Method Of Turnout Area In Metro

With the rapid development of urban rail transit,the problem of train-induced environmental vibration has gradually attracted widespread attention.The vibration has even been listed as one of the seven major environmental hazards.The rigid frog turnout widely used in urban rail transit becomes the most serious vibration pollution source in the line due to its inherent structural irregularity and dense joints.However,at present,the vibration reduction measures are lacking in pertinence at the turnout area.There is a high chance of causing damage to the turnout,deteriorating the rail/wheel contact relationship,and shortening the shock absorption life by copying the vibration reduction measures such as vibration reduction fasteners and floating slabs in the interval line.The problem is the lack of understanding of the vibration excitation source and the lack of standards for vibration assessment in the turnout area.So it is difficult to develop a set of vibration control methods suitable for the turnout.In view of the above problems,this paper took the No.9 simpleopening rigid frog turnout in urban rail transit as the research object.It carried out the research on the vibration prediction method and vibration source intensity characteristics in the turnout area.A fully coupled dynamic model of vehicle-turnout-tunnel-soil system was established,and the prediction and analysis of the whole process from train-induced vibration to propagation of elastic waves were realized under the unified model.Based on the vibration source intensity test and the rail receptance distribution test in the turnout area,the dynamic characteristics and vibration source intensity characteristics of the turnout structure were verified,and the vehicle-turnout-tunnel-soil system fully coupled dynamic model established in this paper was verified.The vibration induced by unique structural irregularity of the turnout track and other types of irregularities and their contribution to the vibration source intensity were analyzed,and detailed correction was put forward for the vibration source intensity of the turnout area.Based on the power flow method,the vibration transfer process of the switch area and the frog area was visualized.The vibration isolation effect of the steel spring floating slab for the turnout was analyzed from the perspective of energy.The elastic shear waves and longitudinal waves in the tunnel wall were analyzed.The energy distribution characteristics of shear waves and longitudinal waves provided a reference for the determination of the vibration source intensity in the turnout area.The main research contents and conclusions stated are as follows:1.The fully coupled model of vehicle-turnout-tunnel-soil systemA fully coupled dynamic model of vehicle-turnout-tunnel-soil system was established.The calculated receptance of railway tracks were compared with the tested receptance in space-frequency distribution law,which verified the accuracy of the model to simulate the dynamic characteristics of the track structure.The acceleration value of tunnel wall vibration calculated by the vehicle-turnout-tunnel-soil system fully coupled model was compared with the field measured value,and the model’s prediction of vibration source intensity was verified from multiple analysis angles of time domain,frequency domain,and time-frequency distribution law accuracy.2.Experimental research on the receptance of railway tracks in turnout areaTaking the No.9 simple turnout as the research object,the vertical and lateral acceleration receptance of various rails in the turnout area were tested through the field hammer impact test,and the receptance of the stock rail,the switch rail,the closure rail and the frog were analyzed by distribution properties in space-frequency domain.The influence of the change of rail section,the change of different rail types,the change of the fastener system,and the complex constraints such as the locking device,the stud,and the filler on the receptance of railway tracks were proved.Based on the receptance,the law of uneven distribution of vertical stiffness in the turnout area along the longitudinal direction was analyzed.3.Experimental research on the characteristics of vibration source intensity in the turnout areaFour groups of No.9 simple turnouts with different service times on the metro lines were selected,and field tests were carried out to test the rail surface roughness,rail profile and vibration source intensity characteristics in the turnout area.Two typical sections of the switch area and the frog area were selected,and the time-frequency distribution law of the vertical and lateral vibrations of the tunnel wall in the switch area and the frog area were investigated.The causes of vibration in the turnout area and the corresponding vibration source strength characteristics were analyzed,which provided verification for the numerical simulation prediction model.4.Research on vibration excitation source and vibration correction term in turnout areaBased on the fully coupled model of vehicle-turnout-tunnel-soil system,the effects of random irregularity,turnout structural irregularity,joint impact,and uneven stiffness distribution on the vibration source intensity were calculated and analyzed.Considering the train running through turnout main/branch in a facing/trailing direction,the time-frequency distribution characteristics of tunnel wall vibration acceleration due to the structural irregularity of the turnout track and the superimposed random irregularity are analyzed.The influence of various vibration sources on the intensity of vibration sources at different train speeds was analyzed.For the vibration correction term of the vibration source intensity on the rigid frog turnout,a detailed correction suggestion was given.5.Visualization research of vibration transfer in turnout area based on power flowBased on the fully coupled model of vehicle-turnout-tunnel-soil system,the structural sound intensity in the tunnel wall section was calculated and analyzed,and the propagation path of vibration energy in the track-tunnel-soil system was visualized in the form of power flow.The vibration energy flow law in different frequency domains was analyzed for the train running through turnout main/branch in a facing/trailing direction,the side reverse direction and the side forward direction.The model of the steel spring floating slab track in the turnout area was established,the distribution of vibration energy in the track layered structure was calculated and analyzed,and the vibration reduction effect of the steel spring floating slab track in the turnout area was evaluated based on the power flow method.The energy distribution and transmission direction of the transverse and longitudinal waves of the tunnel wall were analyzed,which provided a reference for the determination of the location and value of the vibration source intensity in the turnout area.