Experimental research on dynamic response of aeolian sand cored subgrade under train load

Coarse-grained soil fillers are extremely scarce along railways in the desert areas in China. However, there is abundant aeolian sand. Because aeolian sand has defects including being bad-graded and having open grains, it is not suitable to direct use as subgrade fillers. The aeolian sand-cored subgrade takes into account the economic, environmental protection and mechanical properties, it uses aeolian sand along the railway to fill the bottom layer of subgrade, and uses pebble soil to wrap the subgrade slope. By conducting dynamic tests on the novel subgrade, the spatial distribution characteristics of dynamic response and vibration energy of the subgrade and their changes with the train axle load and train speed were obtained. Results are shown as follows. (1) Attenuation of the dynamic stress on the subgrade with the depth is mainly concentrated in ranges of 0～0.6 m and 1.5～2 m below the subgrade surface. Attenuation of the acceleration along the slope is mainly observed in the range 5 m from the track center. The dynamic stress and acceleration amplitude both grow obviously with the increase in the axle load and train speed, while the attenuation rate reduces with the growing axle load. (2) The amplitude spectrum of dynamic stress follows the octave characteristic and the amplitude modulation effect, and the low-frequency vibration at 0～2 Hz exerts a control effect on the dynamic stress. The vibration acceleration level (VAL) is concentrated in the central frequency band of 12.5～31.5 Hz. The VAL in the low-frequency range of 0～10 Hz attenuates violently along the slope, while the VAL in the high-frequency range of 10～40 Hz attenuates slightly. (3) Almost 80% of the total vibration energy is dissipated along the subgrade slope. According to the aggregation quantity of total vibration energy in each frequency band, the frequency bands are listed in a descending order as frequency bands 2, 1, 3, and 4. The energy in each frequency band always grows with the increases in the axle load and train speed while the growth rate decreases progressively with the increase of frequency from frequency band 1 to frequency band 4. © 2024, Central South University Press. All rights reserved.