# A Novel Strutless Double-Row Structure for Deep Excavation: Working Mechanism Study and Analysis
## 3 Analysis of Experimental Results  
### Deformation Analysis  
#### 3.1.1 Horizontal Displacement of Pile Top  
The FRP and BRW are in rigid connection, ensuring that the displacement of the crossbeam accurately reflects the horizontal displacement at the top of the double-row structure. Figure 12 illustrates the progression of horizontal displacement at the pile top throughout the excavation process. As the excavation depth increases, the displacement of the pile top for each supporting structure is observed to rise gradually. This trend is attributed to the increasing lateral earth pressure exerted on the piles as the excavation proceeds. Notably, the displacement rate tends to accelerate with deeper excavation, indicating a potential for increased structural response as the excavation nears completion. The maximum displacement observed in the SPW experiment is 5.061 mm, while the minimum displacement, recorded in the ARPW support with a 6D row spacing, is 0.51 mm. This disparity highlights the superior performance of the DRPW and ARPW structures in controlling displacement, particularly when optimized for row spacing. The steeper slope of the displacement curve for the SPW structure towards the end of the excavation suggests greater instability, which is consistent with the findings of previous studies [6; 38]. These studies have shown that the double-row configuration, with its distribution of loads, provides enhanced stability and control over deformation compared to traditional single-row systems.  
Figure 11: Numerical simulation model.  
Figure 12: Horizontal displacement of pile top during excavation.  
Figure 13 presents a comparison chart illustrating the measured and numerically modeled horizontal displacement of the structure tops for each structure following the excavation. From the chart, the horizontal displacement of the pile top obtained through numerical simulation closely matches the measured displacement of the pile top. The comparison, as depicted in Figures 12 and 13, indicates that both DRPW and ARPW exhibit less horizontal displacement at the pile topes compared to SPW. This observation underscores the superior displacement control capacity of the double-row structure compared to the single-row structure. For the DRPW structures with 2D, 4D, and 6D spacing, the ARPW structures show a significant reduction in final pile top displacement by 25.9%, 44.5%, and 79.7%, respectively. These results confirm the superior displacement control capabilities of the ARPW structure in comparison to the DRPW structure with equivalent spacing. Intriguingly, the DRPW structure exhibits its minimum displacement in the 4D row spacing test, whereas the ARPW structure records its lowest displacement under a 6D row spacing. These findings indicate that the optimal row spacing for the double-row structures supporting structure falls within the range of 2D to 6D, consistent with previous research results [39; 40]. From the numerical modeling results, the minimum displacement for the ARPW structure occurs within the range of 4D to 8D, which lags that of the DRPW structure.