| In recent years,China’s high-speed railway has been vigorously constructed.By the end of 2018,China’s high-speed railway has reached 29,000 kilometers,more than two-thirds of the world’s total high-speed railway mileage.It has become the country with the longest high-speed railway mileage,the highest transport density and the most complex network operation scenario in the world.At the same time,China is also a country with frequent earthquakes,with wide distribution,high frequency and high intensity.The high-speed railway lines are dense and the departure time interval is short,which leads to a great increase in the probability of high-speed train running on track and the risk of train derailment when the earthquake occurs.Therefore,a three-dimensional finite element model of track-subgrade-foundation dynamic interaction under earthquake-train moving load coupling is established to calculate and analyze the environmental vibration characteristics of track,subgrade and foundation.The main contents are as following:(1)The 3D finite element model of track structure-subgrade-foundation is established.The train load unit is nested with ABAQUS by DLOAD subroutine to realize the application of train load.Seismic load is simulated by applying seismic horizontal acceleration at the bottom of the model.By applying viscoelastic boundary to simulate the propagation of wave from finite domain to infinite domain,the number of model elements is greatly reduced,and the calculation time and workload are shortened.The validity of the model established is verified by comparing the vertical dynamic stress and dynamic displacement of the top surface of bed surface.(2)The vibration displacement amplitude,acceleration and frequency spectrum of each structural layer of rail and subgrade in pile-supported subgrade under different conditions are calculated under train moving load.The results show that the amplitude of vertical vibration displacement of rail is larger than that of horizontal vibration displacement,and the amplitude of vertical vibration displacement is about 16 times of that of horizontal vibration displacement.The rail mainly vibrates at high frequency in horizontal direction,and the vertical dominant frequency is widely distributed,with low frequency,intermediate frequency and high frequency all distributed.Compared with free subgrade,the vibration displacement amplitude of pile-supported subgrade is obviously reduced,which is about 45%-60%of that of freestyle subgrade.(3)A three-dimensional finite element model of pile-supported subgrade under seismic load is estabslihed.The influence of pile parameters such as pile diameter,pile length,pile elastic modulus,pile spacing and embankment height in pile-supported subgrade on the dynamic response of rail and roadbed structures under seismic load is discussed.Considering comprehensively,the optimum pile diameter is 0.8m,pile length is 8-10m,pile spacing is 2m and pile elastic modulus is 20GPa,and the embankment height should not exceed 3m.(4)A three-dimensional finite element model is established under coupled seismic and train moving load considering the dynamic interacting of track-subgrade-foundation.The vibration displacement amplitude,acceleration and stress time history of each layer of track and subgrade are all analysed.The results show that the vibration displacement amplitude of rail and subgrade is mainly controlled by earthquake load,and the acceleration is mainly controlled by train load.The acceleration of rail and subgrade increases gradually,but the displacement decreases gradually with the increase of train axle load.With the increase of train speed,the amplitude of vibration displacement of the rail and roadbed tends to decrease first and then increase.After reaching a certain speed,the track acceleration increases again.The vibration acceleration of each layer of subgrade shows the trend of decreasing first and then increasing,and the train speed reaches the final decreasing,which is opposite to the vibration law of the track. |
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