Abstract：The dynamic responses of subgrade, containing dynamic stress, vibration acceleration and vibration velocity, have been obtained in the filed test under EMU load in the Wuhan~Xianning typical section in Wuhan-Guangzhou high-speed railway , carried out separately in the alignment league try stage and during operation after 2 years. In the paper, the relationship of train speed and the dynamic response has been analyzed; the law of dynamic respone along the roadbed depth, and the change of the dynamic respone of subgrade before and after the operation has been discussed. The results indicate that along the subgrade surface cross section, the dynamic stress response has the nonuniform distribution, the measured value under rail bigger than the median line area; the most intense dynamic respones are measured on the surface and graded gravel area; it reduces sharply with the increase of depth. The speed of train loads has a smaller impact on the dynamic stress, while a greater influence on the vibration acceleration. Comparing during operation 2 years later with in the alignment league try stage, the dynamic stress and vibration velocity of the surface layer of subgrade bed differ little, but the corresponding acceleration change greatly. Practical experiments show that the range of attenuation rate of dynamic stress and dynamic acceleration at z=2.7m is respectively 73.40%~79.30% and 79.28%~86.90% , while 82.99%~89.06% and 92.78%~96.31% at z=4.2m; the scope of attenuation rate of vibration velocity at z=2.7m is 75.62%~80.80%.
2013, Vol. 32 
