# Experimental Study on Dynamic Response Characteristics of RPC and RC Micro Piles in SAJBs
## 4 Observations and Conclusions  
To further discuss the dynamic response characteristics of micro pile-soil interaction, the shaking table tests on dynamic response of RPC and RC micro piles have been carried out in this paper. Meanwhile, the natural frequencies, the strains time history of micro piles-soil interaction, the bending moments and deformations of piles have been obtained under sine waves with different frequencies and seismic wave loads. The experimental results are described as follows.  
1. The first and second natural frequencies of the RPC micro pile are about 4.7 Hz and 16.3 Hz, and that of RC are 3.62 Hz and 15.4 Hz, respectively. Moreover, both compactness of sand and the natural frequencies of micro piles are increased under the load of repeated white noise.
2. Compared with the action of sine waves and the action of seismic waves, the frequency of sine wave is relatively monotonous, but the frequency of the seismic wave is abundant, inducing the reverse deformation and bending moment of the pile more remarkable under the dynamic excitation load. It is also found that the dynamic response characteristics of piles under artificial wave were the most significant, which was followed by the EI-Centro wave, and then by the Kobe wave. The responses of piles under seismic wave loads are larger than those of sine waves.
3. The maximum strains of piles were observed at the depth of 4.2 D (D is the diameter of the pile). Meanwhile, the maximum bending moments of the RPC and RC pile appear at the depth of 0.64D and 0.42 D, respectively, under a dynamic excitation. The peak horizontal deformations of piles were demonstrated at the pile head.
4. Compared with the dynamic responses of the RC pile, it can be seen that the bending moments and the strain responses of RPC are larger than that of the RC pile, and the maximum increased by 40% and 98%, respectively. In addition, although the horizontal displacements of the RC pile are larger than that of the RPC pile, the increments are slight at only the range of 15%. Therefore, the RPC micro pile with steel fiber has better crack resistance, higher ductility, and flexural rigidity than that of the RC pile.  
In addition, due to the relatively small amount of specimen, as well as the influence of artificial factors such as specimen fabrication, the measuring method, and so on. A large number of experimental data points need to verify the dynamic response performances of micro pile-soil interaction under shaking table tests.  
All authors substantially contributed to this work. [PERSON] and [PERSON] designed and fabricated the micro-pile model. [PERSON], [PERSON], and [PERSON] designed the experiment. [PERSON] and [PERSON] performed the experiments, analysis. [PERSON], [PERSON] ([PERSON]) wrote the paper and [PERSON] ([PERSON]) revised and finalized the paper. All authors helped with the writing of the paper.  
The authors gratefully acknowledge the financial supports provided by the Natural Science Foundation of China with Grants Nos. 51778147, the National key fundamental Research and development Funds for the 13 th five-year Plan (2016 YFC0701700), and the Hunan Provincial Innovation Foundation for Postgraduate.  
The authors declare no conflict of interest.