(1. Key Laboratory of Karst Environment and Geological Hazards，Ministry of Land and Resources，Guizhou University，Guiyang，Guizhou 550025，China；2. Northwest Research Institute Co. Ltd. of CREC，Lanzhou，Gansu 730070，China；3. College of Resources and Environmental Engineering，Guizhou University，Guiyang，Guizhou 550025，China；4. College of Civil Engineering and Architecture，Southwest University of Science and Technology，Mianyang，Sichuan 621000，China)
Abstract：In order to further study the dynamic characteristics and deformation characteristics of a new type of long-short pile composite foundation with part-screw pile + cement soil compaction pile under long-term train load，the indoor dynamic model test of long-short pile composite foundation was carried out. The time-frequency domain characteristics，sub-band energy distribution and energy attenuation law of vibration response signal were analyzed，and the spatial transmission characteristics of vibration energy of long-short pile composite foundation were revealed. Based on the method of wavelet packet energy analysis，a vulnerability evaluation index ?ERMS was established，and the identification effect of ?ERMS index was verified by the dynamic strain response of piles and the displacement response of the soil between piles. The results show that：(1) The frequency of the vibration signal of the composite foundation of part-screw pile + cement soil compaction pile is mainly distributed in the range of 0–25 Hz，and the characteristic frequency causing the peak vibration response is mainly concentrated near the natural frequency of the train. (2) During the propagation of the vibration wave along the soil medium between the piles，part of the high frequencies are filtered out and the low frequency part continues to propagate，at a distance from the surface of the foundation the vibration energy is mainly concentrated in the low frequencies. (3) The vibration energy of the pile and the soil between the piles decays faster at the shallow level of the foundation but slows down as the depth of the foundation increases. (4) The ?ERMS index value has a good identification effect on the vulnerability of the pile. The vulnerability of the middle part of the long pile and the short pile is the largest，which belongs to the weak part of the vibration resistance. (5) The displacement of soil between piles increases gradually with the increase of vibration times. The value of ?ERMS index cannot effectively distinguish the damage and deformation degree of soil. The research results have certain reference significance for the engineering design of long-short pile composite foundation under train load.
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2024, Vol. 43 
