Research On Prediction Method Of Induced Earth Vibration By High-speed Train

The rapid development of high-speed rail has brought many conveniences,shortening travel times and boosting economic development,as well as environmental vibration and noise problems.The vibrations induced by high-speed trains affect the daily work and life of residents near the track,as well as the safety of buildings and the measurement accuracy of precision instruments.Therefore,it is of great significance to study the prediction method of high-speed train induced earth environmental vibration,and grasp the main excitation mechanism,relevant factors affecting vibration source,and vibration propagation law of high-speed railway line,which is of great significance for the design of high-speed railway line,reducing structural vibration noise and protecting the environment.Firstly,the research and prediction methods of environmental vibration of high-speed railways at home and abroad are summarized,and on the basis of the research of FTA environmental vibration prediction method,a prediction method for calculating train load density based on the nonlinear coupling model of vehicle track is proposed,and the transfer admittance prediction method is obtained by two methods: actual measurement and simulation.Secondly,by establishing the track-semi-infinite region geodetic model under point source impact loading,the analytical formula for predicting the acceleration of earth vibration caused by the train running on the track is derived.Then,according to the prediction formula,the dynamic model of the train-track nonlinear coupling system is established,and the program is compiled by MATLAB mathematical tools,and the cross-iteration algorithm is used to solve the problem,and the load density function of the 1/3 octave train is calculated.After that,the line source transfer admittance was obtained through the earth hammering test and finite element simulation,and the prediction formula was substituted to obtain the prediction result.Finally,the comparative analysis with the field measurement verifies the correctness of the prediction method proposed in this paper to calculate the train load density based on the track model,and obtain the transfer admittance through two methods: actual measurement and simulation.The results show that:(1)Based on the train load density function,line-source vibration transfer admittance and the coupling between building and ground,the track-semi-infinite region geodetic model under point source impact load is established,and the analytical formula for predicting the geodetic acceleration caused by the train running on the track is derived,which provides a theoretical basis for constructing the rail transit environmental vibration prediction method.(2)By establishing the dynamic model of train-track nonlinear coupling system,a numerical method for solving the dynamic equation of train-track coupling system and calculating train load density using cross-iterative algorithm is proposed,which avoids the problem of measured train load density function in the existing research methods,and makes the prediction method more practical and operable.In addition,under different speed conditions,the train load density function showed a trend of first rising and then decreasing,and with the increase of speed,the train load density function also increased significantly.The track structure has almost no effect on the train load density function when the center frequency is in the low frequency,mainly in the frequency band with a high center frequency,and the train load density function under the ballastless track structure is greater than the train load density function under the ballasted track.(3)Through the field test of earth hammering,a large open space near the Changjiu intercity railway line without interference from other environmental factors such as vibration sources was selected as the test site,and the hammering test at different excitation positions was designed,which proved the feasibility of using the shock load to measure the vibration transfer admittance of the large site source,and then using the numerical integration formula to calculate the admittance of the vibration transfer of the line source.(4)By establishing a three-dimensional dynamic finite element model of the soil layer,the pulse load is applied to the earth surface to simulate the vibration propagation of the land surface,which is used as the second method to calculate the admittance of line source vibration transfer.Consulting the geological data to determine the relevant parameters of the soil layer is done with the help of the large finite element software ANSYS.The acceleration time history data of the vibration response is extracted,and then the numerical integration formula is used to calculate that with the increase of the center frequency,the line source transfer admittance shows a trend of first rising and then decreasing.(5)A prediction method based on the model to calculate the load density of the train and the vibration transfer admittance of the ground line source measured on site is proposed,and the prediction results are in good agreement with the measured data,and the maximum error is2.8%,which shows the correctness of the prediction method.This method avoids the problem of measuring the load density of the train,and accurately obtains the transfer admittance of the test area through field tests,which has the characteristics of high prediction accuracy and easy implementation.(6)The second prediction method of calculating the load density of the train based on the model and the simulation calculation of the vibration transfer admittance of the earth line source is proposed,and the prediction results are in good agreement with the measured data,and the maximum error is 4.08%,which reflects the correctness of the prediction method.(7)The train load density function can be calculated based on the track model,which is easier to implement than the actual measurement;The prediction method of line source transfer admittance obtained by the earth hammering test is high,and the prediction accuracy is high,but the field test is large and difficult to test.The prediction method 2 of line source transfer admittance calculated by the established soil simulation model is realized through finite element software modeling,which solves the difficulty of field test and is easy to operate,but the prediction accuracy is lower than that of the prediction method.