# A Novel Strutless Double-Row Structure for Deep Excavation: Working Mechanism Study and Analysis
## 4 Engineering Example  
This study focuses on the foundation pit engineering of the south side plot of Jinzhonghe Avenue in Tianjin, analyzing the support performance of the ARPW structure. The project, located in Tianjin's Hebei District, includes six high-rise buildings, four multi-story buildings, and a one-story basement (partially extending to a  
Figure 27: Comparison of bending moment (H = 500 mm). Figure 26: Comparison of 6D bending moment with excavation. second underground floor). The excavation area measures approximately 25,700 m\({}^{2}\), with a depth of 4.5 m. The western side of the underground structure is 3.6 m from the red line boundary, and a six-story residential building is situated 7.4 m outside this boundary. Traditional cantilever support methods are inadequate for ensuring the safety of surrounding buildings and subway lines in localized engineering areas. Implementing a single-row pile with an overall horizontal support system would complicate soil removal and increase construction time and costs. Therefore, at the A-A cross-section, the project utilizes a DRPW structure. Both the front and rear piles are 11 m long, with a diameter of 0.6 m, a center-to-center distance of 2 m, and a spacing of 2.2 m between the front and rear rows. The foundation pit layout is depicted in Figure 28. To ensure safe excavation and assess the performance of the support structure, the displacement of pile tops and deep displacement of support piles were monitored. The lateral displacement of the DRPW structure was measured using an inclinometer. The measured displacement of the front piles is illustrated in the figure below. The inclinometer results of the A-A cross-section support piles are shown in Figure 29. It is evident from Figure 29 that the deformation pattern of the support piles resembles that of SPW with a horizontal support at the top. The maximum horizontal displacement of the front piles of the DRPW structure is 14.2 mm. To further investigate the deformation characteristics of the support structures and compare the performance of irregular double-row piles, this study employed Abaqus 2016  
Figure 28: Foundation pit plan. Figure 29: Horizontal displacement of the front pile. software to create numerical models of SPW, DRPW, and ARPW structures based on the project's real support structure. The modeling approach used is similar to that described for the previous models and will not be reiterated here. The dimensions of the pile structures in each model were constructed according to the actual dimensions of the DRPW structure, and the settings were consistent with the previously described numerical models. The rear wall of the ARPW was set to a thickness of 0.4 m, and the spacing between piles was kept consistent with that of the DRPW structure (as shown in Figure 30). The properties of each soil layer are presented in Table 5. The distance of the left boundary from the pile wall and the height of the model are both 20 m. The displacement diagrams of the piles obtained from the simulations are shown in Figure 29. From the figure, the horizontal displacement of the pile obtained through numerical simulation closely matches the measured displacement of the pile top. Using the DRPW structure as an example, it can be observed that the simulated horizontal displacement of the front piles of the model is consistent with the trend of the measured horizontal displacement, with a maximum pile displacement of 13.5 mm. The calculated maximum error between the simulated and measured horizontal displacements above the excavation surface is 9%, which is within an acceptable range. The comparison of the obtained horizontal displacement data of the piles reveals that the maximum horizontal displacements of the SPW, DRPW, and ARPW structures are 22.0 mm, 13.3 mm, and 9.9 mm, respectively. The maximum pile displacement of the DRPW and ARPW structures is reduced by 39.5% and 55%, respectively, compared to the SPW structure.