## 2 Experimental Test
### Experimental Results
#### 2.5.4 Earth Pressure  
To eliminate the influence of the initial value difference on the measured data, the earth pressure gauge was set to zero after filling the sand and completing the installation of the specimen. The earth pressure-displacement (\(p\)-\(u\)) curves of different test cases are illustrated in Figure 11. The \(p\)-\(u\) curves of the test cases under push \(u_{\text{t}}\) are significantly different from those under pull \(u_{\text{t}}\). Under push \(u_{\text{t}}\), with an increase in \(u\), the \(p\) of \(S_{4}\) (the distal end of the FAS specimen) first rapidly increases, and then slightly increases, as shown in Figure 11a. With an increase in \(H,p\) increases up to a maximum value of \(56.78\) kPa. This is because, with an increase in \(u\), the sand at the distal end of the FAS specimen gradually approaches the limit bearing capacity state, and a slip surface is formed near the distal end of the FAS specimen. When a slip surface is formed, the peak resistance of the sand to the FAS specimen can be obtained, and the increment in \(p\) is significantly reduced. With an increase in \(H\), the effective vertical stress in the sand increases, resulting in the increment of the earth pressure at the distal end of the FAS specimen. With an increase in \(u\), the FAS specimen gradually moves away from the front wall. The \(p\) of \(S_{1}\) to \(S_{3}\) (lower part of the front wall) and \(S_{5}\) (upper part of the front wall) are nearly zero. This is because, when the FAS specimen gradually moves away from the front wall, the earth pressures of \(S_{1}\) to \(S_{3}\) and \(S_{5}\) decrease from the static earth pressure to the active earth pressure. The sand in some positions may even separate from the front wall to form voids. Under pull \(u_{\text{t}}\), with an increase in \(u\), the \(p\) of \(S_{5}\) (upper part of the front wall) rapidly increases firstly, and then slightly increases, as shown in Figure 11b. This is because the earth pressure of \(S_{5}\) increases from the static earth pressure to the passive earth pressure. The maximum \(p\) is \(14.64\) kPa when \(H\) is \(63\) cm. With an increase in \(H\) and \(u\), the \(p\) of \(S_{1}\) to \(S_{3}\) (lower part of the front wall) increased. The reason for this is that the mass of the \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Parameters** & \(x_{\text{1a}}\) & \(x_{\text{1b}}\) & \(w_{\text{1}}\) & \(v_{\text{s1}}\) & \(x_{\text{2a}}\) & \(x_{\text{2b}}\) & \(w_{\text{2}}\) & \(v_{\text{s2}}\) & \(\theta_{\text{1b}}\) & \(\theta_{\text{2a}}\) & \(\theta_{\text{2b}}\) \\ \hline
**Units** & & **m** & & **mm** & & **m** & & **mm** & & \({}^{\circ}\) & \\ \hline H21-Push & / & / & / & / & 2.05 & 2.47 & 0.42 & 40 & / & / & 36 \\ H31.5-Push & 0.13 & 0.19 & 0.06 & \(-55\) & 1.91 & 2.74 & 0.83 & 38 & 71 & 53 & 39 \\ H63-Push & 0.12 & 0.39 & 0.27 & \(-42\) & 1.67 & 3.04 & 1.36 & 36 & 70 & 49 & 38 \\ H21-Pull & / & / & / & / & 2.10 & 2.23 & 0.13 & \(-72\) & / & / & 74 \\ H31.5-Pull & 0.00 & 0.32 & 0.32 & 18 & 1.94 & 2.19 & 0.24 & \(-38\) & 35 & 78 & 76 \\ H63-Pull & 0.00 & 0.82 & 0.82 & 15 & 1.90 & 2.26 & 0.35 & \(-35\) & 32 & 65 & 77 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of sand surface deformation. FAS specimen and the sand above it produce additional stress on the sand below it [49]. The magnitude of the stress is proportional to the mass of the FAS specimen and the sand above it, and inversely proportional to the distance from the mid-length point of the lower surface of the FAS specimen. Therefore, with an increase in \(u\), the FAS specimen moves closer to the front wall. From \(S_{1}\) to \(S_{3}\), the corresponding distance to the mid-length point of the lower surface of the FAS specimen decreases, resulting in a larger additional stress and an increment in \(p\). With an increase in \(H\), the mass of the FAS specimen and the sand above it increase, resulting in a larger additional stress and an increment in \(p\). In addition, the maximum \(p\) decreases from \(S_{1}\) to \(S_{3}\).