# Experimental Study on Dynamic Response Characteristics of RPC and RC Micro Piles in SAJBs
## 2 Experimental Program
### Soil Container and Soil Parameters  
The sand used in this test was from Min River in the Fujian province, China, where a number of SAJBs were constructed. The natural sandy soil was dried to reduce water content and filtered to remove impurities as well as large particles before the test. The nonuniform coefficient Cu = 3.16, which \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Specimen**} & **Diameter** & **Moment of** & **Modulus of** & **Relative** & **Flexural** & \multirow{2}{*}{**Section**} \\  & **(mm)** & **Inertia \(I\)** & **Elasticity \(E\)** & **Pile Length** & **Rigidity** & **Rigidity** \\  & **(\(\times\)10\({}^{-5}\) m\({}^{4}\))** & **(\(\times\)10\({}^{4}\) MPa)** & **z (m)** & **(kN-m\({}^{2}\))** & **(kN-m\({}^{2}\))** \\ \hline RPC pile & \multirow{2}{*}{100} & \multirow{2}{*}{0.49} & 4.41 & 3.49 & 216.7 & \multirow{2}{*}{circular} \\ \cline{1-1} \cline{5-6} RC(C40) pile & & & 3.25 & 3.78 & 159.3 & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of micro piles. Figure 2: Micro pile models (unit. mm). (**a**) Fabrication of micro-piles. (**b**) Reinforcement drawing. means the soil was basically homogeneous [33]. [PERSON]'s ratio was calculated by the Kulhawy method (1990) [34]. Its average SPT blow counts of the sand were 12. According to ASTM Standards [35], it is classified as medium sand. The parameters of sand are listed in Table 2.  
The boundary condition is a crucial factor to investigate the dynamic response of micro pile- soil interaction in this study. Theoretically, the larger the soil box, the more accurate the results. However, as a consideration of the lab space and economy, the dimensions of the soil box are usually of a limited size. [PERSON] et al. [36] conducted shaking table experiments and numerical analysis on the structure-soil interaction. It was concluded that, when the plan dimension of the soil box is five times that of the structure, the experimental errors caused by the boundary condition are small. In addition, the FEM method [37] was employed to analyze the soil box and determine the dimensions of the soil box. It indicated that the influence of the boundary can be neglected when the radius of the soil box is larger than five times of the pile's diameter. Based on the above results, a rigid square steel box with a width of 2.0 m, length of 2.0 m, and height of 2.1 m and wall thickness of 10 mm was employed to constrain the soil, as shown in Figure 3a. The soil box was welded by four steel plates of 10 mm thickness, and each steel plate was stiffened by a number of diagonal braces around its outside edge. In order to facilitate sand filling and unloading, three square steel plate doors with the dimensions of \(200\times 200\times 10\) mm were designed on three sides, respectively, at the lower outside surface of the steel plate, and these doors were closed when sand is filling into the soil box. The length and width of the soil box are approximately 20 times diameter of the micro-pile, which is sufficient to consider the boundary condition. The bottom of this box was welded to a bottom plate with dimensions of \(2200\times 2200\times 10\) mm. The bottom plate was then anchored on the shaking table surface by high-strength bolts through numerous screw rods with 16 mm in diameter to achieve a fix base condition, as shown in Figure 3a. To eliminate the deformation of the steel box for too small of a stiffness during seismic wave loading, a total of eight inclined angle steels were used as support on the outer side of the steel box. Four 150-mm long, steel angles were welded inside the box to the center of the bottom plate to fix the micro pile at its end tips before the steel box is filled with sand, which is shown in Figure 3b.