Experimental research on dynamic response characteristics of transition subgrade induced by heavy-haul trains

The dynamic responses of subgrade under moving train loads can provide reference for subgrade settlement prediction, condition evaluation and so forth. The field dynamic tests were conducted on transition subgrade in Shuo-Huang heavy-haul railway in China. The variation rules of peak dynamic displacements along the track and the subgrade slope were analyzed, and the random distribution characteristics of the peak dynamic displacements at subgrade shoulder were studied. The response characteristics of subgrade during the train passage were investigated, and the attenuation regularities of vibration along the subgrade slope were revealed. The results indicate that the action of train moving loads on subgrade has obvious periodicity, and two bogies in the adjacent wagons can be regarded as one loading unit. The peak dynamic displacements at the subgrade shoulder obey normal distribution under the repeated loading of the loading units. The vibration frequency mainly distributes between 0 and 20Hz under the loading of heavy-haul trains. The vibration energy attenuates severely from the subgrade shoulder to the slope toe. The subgrade bed is influenced dramatically by dynamic loadings of trains, and moving train loads have little influence on the part below the subgrade bed. The research results can provide basis for the evaluation of instantaneous and long-term dynamic stability of subgrade, and offer guidance for simulating the train moving loads precisely in model test and numerical analysis to study the dynamic response of subgrade. © 2019, Editorial Office of China Civil Engineering Journal. All right reserved.