## 3 Experimental Setup and Procedure
### Soil  
Fujian sand, the Chinese standard sand adopted in the experimental program, was classified as well-grade sand (SW with a uniformity coefficient \(C_{\rm u}\) = 5.5, curvature coefficient \(C_{\rm c}\) = 2.7, and angular soil particles) as per the Chinese code GB/T 2021 [32] and the given grading curve (Figure 6). The minimum and maximum relative densities of the sand were further tested according to the Chinese code GB/T 2019 [33]. The test results indicated that the maximum and minimum dry unit weights of the well-graded sand were \(\gamma_{\rm{dmax}}\) = 18.2 kN/m\({}^{3}\) and \(\gamma_{\rm{dmin}}\) = 15.3 kN/m\({}^{3}\), respectively, (i.e., maximum void ratio \(e_{\rm{max}}\) of 0.718 and minimum void ratio \(e_{\rm{min}}\) of 0.441). The unit weight and moisture content of the fill were measured for each  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameters** & **Model** & **Prototype** & **Similarity Ratio** \\ \hline Width of pile cross-section (m) & 0.04 & 1.2 & 1:30 \\ Pile length (m) & 0.8 & 24 & 1:30 \\ Pile spacing (m) & 0.2 & 5 & 1:25 \\ Length of segment above ground (m) & 0.04 & 1 to 2 & 1:25 to 1:50 \\ Pile embankment distance (m) & 0.04 & 1 to 2 & 1:25 to 1:50 \\ Elastic modulus of piles (GPa) & 34.25 & 35.0 & 1:1.02 \\ Unit weight (kN/m\({}^{3}\)) & 17.7 & 17.9 & 1:1.01 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Parameters and similarity ratios of the model and prototype.  
soil layer using the oven drying method [33]. The average unit weight was \(\gamma=17.7\) kN/m\({}^{3}\), and the average moisture content was \(\omega=2.0\%\) (i.e., the relative density \(D_{\rm r}=65.8\%\), void ratio of \(e=0.536\)). In addition, the internal friction angle and specific gravity of the soil were \(\varphi=40^{\circ}\) and \(G_{\rm s}=2.68\), respectively, given by the direct shear test (sampled from the cutting ring) and specific gravity test [33]. The above parameters were also listed in Table 3 for convenience of query. In addition, the compression modulus of the sand was not accurately measured in this study because it is more difficult to measure sand that can be easily disturbed than cohesive soil, and a value smaller than the actual one would probably be obtained by potential human error. Interested readers can further obtain the compression modulus (or elastic modulus) closer to the actual one from the engineering experience and relevant references such as codes [34; 35; 36], handbooks [37], and studies [11; 38].  
Figure 5: Layout of the model tests: (**a**) planar graph; (**b**) elevation graph; (**c**) locations of instrumentations.  
In this study, focusing on the effects of pile inclination and pile tip constraint rather than the effect of sand relative density, only a uniform density is required without reaching a specific relative density using a delicate sand-raining device. The soil sample was rained from approximately 1.5 m above the soil level in the test tank as in [PERSON] et al. [15] and [PERSON] et al. [4], and the sand was evenly deposited and compacted in lifts to the designated depth. The uniformity of the fill was guaranteed by continuously checking the unit weight of the sample of each layer.