## 4 Experimental Results
### Failure Mode
For instance, \(\varepsilon_{\mathrm{(AB)-10 mm}}\) represents the \(\varepsilon\) on the back side of the abutment at a \(d\) value of \(-10\) mm. There were no cracks in the abutment of the IAP specimen at a \(d\) value of 40 mm (which is the maximum \(d\) value in the literature [36]), as shown in Figure 11a. For the GIAP specimen, under a negative \(d\), \(\varepsilon_{\mathrm{(AB)}}\) changed from tensile to compressive, and \(\varepsilon_{\mathrm{(AF)}}\) changed from compressive to tensile, respectively, from top to bottom, along the \(d_{\mathrm{E(A)}}\), as shown in Figure 10a. The tensile \(\varepsilon_{\mathrm{(AB)}d}\) was observed to be within the range of the \(d_{\mathrm{E(A)}}\), from 0.47 m to 0.75 m, with a peak value at a \(d_{\mathrm{E(A)}}\) of 0.65 m. The compressive \(\varepsilon_{\mathrm{(AB)}d}\) was observed to be within the range of the \(d_{\mathrm{E(A)}}\), from 0.2 m to 0.47 m, with a peak value at a \(d_{\mathrm{E(A)}}\) of 0.4 m. The compressive \(\varepsilon_{\mathrm{(AF)}d}\) was observed to be within the range of the \(d_{\mathrm{E(A)}}\), from 0.44 m to 0.65 m, with a peak value at a \(d_{\mathrm{E(A)}}\) of 0.65 m. The tensile \(\varepsilon_{\mathrm{(AF)}d}\) was observed to be within the range of the \(d_{\mathrm{E(A)}}\), from 0.2 m to 0.44 m, with a peak value at a \(d_{\mathrm{E(A)}}\) of 0.4 m. With an increase in \(d\), the peak tensile \(\varepsilon_{\mathrm{(AB)}d}\) increased progressively. When  
Figure 9: Concrete strain of the pile: **(a)** IAP under a negative \(d\); **(b)** GIAP under a negative \(d\); **(c)** IAP under a positive \(d\); **(d)** GIAP under a positive \(d\). The points with a tensile strain larger than 200 \(\mu\varepsilon\) were emphasized by red dash circle. \(d\) was \(-50\) mm, the peak tensile \(\varepsilon_{\text{(AB)}d}\) (219.73 \(\mu\epsilon\)) exceeded 200 \(\mu\epsilon\), while the peak tensile \(\varepsilon_{\text{(AF)}d}\) was 139.37 \(\mu\epsilon\). Cracking on the back side of the abutment for the GIAP specimen could not be observed during the test because of the filled sand. For the GIAP specimen, under a positive \(d\), the \(\varepsilon_{\text{(AF)}}\) changed from tensile to compressive, and the \(\varepsilon_{\text{(AB)}}\) changed from compressive to tensile, from top to bottom, along the \(d_{\text{E(A)}}\), as shown in Figure 10b. The tensile \(\varepsilon_{\text{(AF)}d}\) was observed to be within the range of the \(d_{\text{E(A)}}\), from 0.46 m to 0.65 m, with a peak value at a \(d_{\text{E(A)}}\) of 0.65 m. The compressive \(\varepsilon_{\text{(AF)}d}\) was observed to be within the range of \(d_{\text{E(A)}}\), from 0.2 m and 0.46 m, with a peak value at a \(d_{\text{E(A)}}\) of 0.4 m. The compressive \(\varepsilon_{\text{(AB)}d}\) was observed to be within the range of the \(d_{\text{E(A)}}\), from 0.43 m to 0.75 m, with a peak value at a \(d_{\text{E(A)}}\) of 0.55 m. The tensile \(\varepsilon_{\text{(AB)}d}\) was observed to be within the range of the \(d_{\text{E(A)}}\), from 0.2 m to 0.43 m, with a peak value at a \(d_{\text{E(A)}}\) of 0.4 m. With an increase in the \(d\), the peak tensile \(\varepsilon_{\text{(AF)}d}\) increased progressively. When the \(d\) was +50 mm, the peak tensile \(\varepsilon_{\text{(AF)}d}\) (202.09 \(\mu\epsilon\)) exceeded 200 \(\mu\epsilon\), while the peak tensile \(\varepsilon_{\text{(AB)}d}\) was 64.24 \(\mu\epsilon\). Cracks on the front side of the abutment for the GIAP specimen were found at a \(d_{\text{E(A)}}\) of 0.65 m (Figure 11b). Figure 11: Damage to the abutment: (**a**) IAP [36]; (**b**) GIAP. Figure 10: Concrete strain of the abutment in the GIAP specimen: (**a**) negative \(d\); (**b**) positive \(d\). The points with a tensile strain larger than 200 \(\mu\epsilon\) were emphasized by red dash circle. The failure modes of the piles and abutments in the IAP and GIAP specimens were analyzed based on \(\varepsilon_{\text{(PB),}d}\), \(\varepsilon_{\text{(PF),}d}\), \(\varepsilon_{\text{(AB),}d}\), and \(\varepsilon_{\text{(AF),}d}\) in Figures 9 and 10.