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Abstract: A two-and-a-half-dimensional finite element model (2.5D FEM) was developed to investigate dynamic responses of the tracks and saturated porous ground subjected to moving loads caused by high-speed trains. The governing equation was derived from the Boit''s theory in frequency domain by applying the Fourier transform with respect to time, and 2.5D finite element equations in u–p format were then established using Galerkin method. The track structure was simplified as an Euler beam resting on a saturated layered porous half-space. The wave-number transform in the load moving direction was employed to reduce the three-dimensional (3D) dynamic problem to a two-dimensional one. The visco-elastic artificial boundary was derived for the saturated soil in the 2.5D FEM by assuming a semi-cylindrical wave front of body wave. The proposed approach was verified by the semi-analytical solutions for a 3D saturated half space subjected to a moving load. The results show that the vertical displacement of elastic medium is greater than that of saturated medium when the train speed is low, while smaller when the train speed becomes high. A large vertical displacement occurs when the train speed is greater than or approaches the shear-wave velocity of the saturated ground. The ground vibration is dominated by either the track resonance in the near-track zone or the train speed in the far-track zone. The attenuation of vertical displacement becomes much slow along distance for high-speed moving trains, and the decay can hardly take place beyond a certain distance from the track center. [Copyright &y& Elsevier]

Environmental vibrations induced by subway operation are harmful to human health and structures when they exceed a certain value. Therefore, effective measures should be taken to reduce the noise and vibration generated by the metro. Therefore, a method to reduce the vibration by the installation of honeycomb Duxseal-cement columns under the ballast is presented in this paper. A honeycomb Duxseal-cement column was embedded in the subgrade of Qingdao Metro Line 13. A field test to measure the vibration of Qingdao Metro Line 13 was conducted. In addition, the time history curve of the vibration acceleration was obtained by processing the data and a Fourier transform was conducted for the test data to obtain a corresponding frequency spectrum curve. The spectrum curve was then converted into the one-third octave spectrum. Finally, the average value of the frequency vibration levels was determined. The comparison between the vibration generated by the metro filling and non-filling Duxseal-cement columns was investigated in detail. The test results show that the subgrade of metro in-filled by the Duxseal-cement columns obtains a better isolation effect than that of non-filling Duxseal-cement columns. The honeycomb Duxseal-cement columns present in the metros decrease their vibration accelerations in three directions, the X-, Y-, and Z-directions, by 33%, 28%, and 40%, respectively, compared with the original. • Vibration reduction effectiveness for metro by Duxseal-cement is investigated. • Field test characterized Duxseal-cement with good wave absorption capability. • Vibration characteristics of ground vibrations due to metro were analyzed. [ABSTRACT FROM AUTHOR]

In this Technical Note, a new material (i.e., Duxseal) with high damping ratio is introduced to the wave impeding block (WIB) as an active vibration isolating barrier in the free field. To evaluate the performance of the Duxseal-WIB (DXWIB), a set of field tests are performed at three test sites of Jinan-Qingdao high-speed railway of China subjected to a moving load at a high speed of 250 km/h. Accelerations in the X-, Y-, and Z-directions are monitored at multiple distances away from the track. Characteristics of ground vibrations in both time and frequency domains are analyzed using the test data. The effectiveness of DXWIB in reducing the level of ground vibration is discussed and demonstrated by comparing with the case with traditional WIB. • A new barrier Duxseal-WIB is developed to apply to high speed railway. • Excellent isolation effectiveness of Duxseal-WIB is confirmed. • Difference of effectiveness between DXWIB and traditional WIB are compared. [ABSTRACT FROM AUTHOR]