# A Novel Strutless Double-Row Structure for Deep Excavation: Working Mechanism Study and Analysis
## 3 Analysis of Experimental Results
### Deformation Analysis
#### 3.1.3 Ground Settlement and Pit Bottom Uplift  
Figure 16 provides a comparison of soil settlement outside the excavation pit for each supporting structure during a 500 mm excavation for each round of excavation. The figure reveals a consistent pattern across all supporting structures; the soil settlement is greatest immediately behind the piles and diminishes progressively as the distance from the piles increases. The overall surface settlement forms a triangular pattern, which aligns with previous findings [40; 41].  
Figure 15: Horizontal displacement contour diagram (H = 500 mm). (**a**) SPW; (**b**) DRPW (4D); (**c**) ARPW (4D).  
At the same excavation depth, the soil settlement values vary among the different supporting structures. The SPW structure records a maximum settlement value of 1.01 mm, while the ARPW structure at a 6D row spacing exhibits the lowest settlement value of 0.228 mm at 120 mm from the supporting structure. In both the DRPW and the ARPW structures, the maximum settlement outside the excavation pit varies with the row spacing. Specifically, under a 2D row spacing, the DRPW structure experiences a maximum settlement of 0.712 mm, while the ARPW structure shows a slightly lower settlement of 0.482 mm. As the row spacing increases to 4D, the maximum settlement for the DRPW and ARPW structures decreases to 0.427 mm and 0.288 mm, respectively. Further increasing the row spacing to 6D results in a maximum settlement of 0.437 mm for DRPW and 0.228 mm for ARPW. The settlement outside the pit under the 4D DRPW, 6D DRPW, and 2D ARPW row spacings are relatively similar. At the same row spacing, it is evident that the ARPW structure exhibits superior control over settlement outside the excavation compared to the DRPW structure. Under 2D, 4D, and 6D rows, the average soil settlement at the observation points decreases by 32.3%, 32.5%, and 34.1%, respectively.  
Figure 17 depicts the displacement value of pit bottom uplift after excavation in the numerical simulation, a parameter that is challenging to monitor in model testing. The figure reveals that the distribution pattern of pit uplift values is inversely proportional to the settlement outside the pit. The soil uplift value in front of the pile is the smallest, and it progressively increases as one moves farther away from the supporting pile. Notably, there is no significant change beyond approximately 1000 mm from the pit wall. Additionally, uplift values differ notably among various structures, while variations within the same structure at different row spacings are relatively minor, consistent with prior research findings [40,42]. The SPW structure's maximum uplift value is 0.57 mm, whereas the DRPW structure reaches a maximum uplift value of 4.4 mm. Remarkably, the ARPW structure's maximum uplift value is 0.27 mm lower than others, resulting in a 22.8% reduction for the DRPW structure and a 52.6% reduction for the ARPW structure when compared to the SPW structure.  
Figure 16: Ground settlement outside the excavation pit (H = 500 mm).