# A Novel Strutless Double-Row Structure for Deep Excavation: Working Mechanism Study and Analysis
## 6 Conclusions  
The ARPW structure represents an innovative, strut-free support system. In this paper, the deformation and stress characteristics and working mechanism of the ARPW structure, the DRPW structure, and the SPW structure are studied through indoor physical model tests and numerical simulation experiments. The key findings are as follows:  
1. The ARPW structure excels in controlling horizontal pile displacement and settlement outside the pit, outperforming both the DRPW and SPW structures. Although maximum lateral displacement occurs in the pile body for both ARPW and DRPW, the ARPW structure minimizes this displacement and directs it downward, leading to the smallest maximum lateral displacement across all row spacings. Soil settlement follows a triangular pattern for all structures, peaking behind the piles and diminishing with distance. Consistently, the ARPW structure achieves the lowest settlement outside the pit, regardless of row spacing. 2. The earth pressure distribution in DRPW and ARPW structures shows distinct patterns. As row spacing increases, the earth pressure against the pile walls in both structures rises, leading to an unloading effect above the excavation and a steep increase in pressure below. In ARPW structures, the earth pressure in front of the pile peaks in the middle, with lower values at the ends, and this pattern becomes more pronounced with wider row spacings. In contrast, DRPW structures exhibit a decrease in earth pressure in front of the piles with increasing row spacing. 3. The ARPW structure features a more evenly distributed bending moment compared to the DRPW and SPW structures. Both the DRPW and ARPW structures exhibit reverse bending points in their bending moment profiles. As excavation depth increases, the maximum bending moments rise, but the ARPW structure's maximum moment point is notably higher, displaced upward by 100 mm to 200 mm relative to the DRPW structure. 4. The ARPW structure capitalizes on the spacing effect, soil gravity, and back wall friction to achieve a balanced structural stress and enhanced anti-overturning capabilities, outperforming the DRPW structure in support performance. ARPW's larger contact area with the soil behind the piles allows for more effective use of frictional resistance and soil weight to counteract overturning moments, leading to a more stable and efficient support system. With equal pile lengths, the ARPW structure exhibits reduced deformation and a more uniform distribution of internal forces, along with improved anti-overturning strength. Experiments highlight that enhancing the transverse dimension of the support structure and utilizing soil stiffness between piles is effective for improving excavation stability. 5. Both ARPW and DRPW structures exhibit improved support capacity with increased row spacing up to an optimal range. DRPW performs best with row spacings between 2D and 6D, while ARPW thrives with 4D to 8D spacing. Beyond these ranges, the effectiveness plateaus, indicating the importance of avoiding overly wide row spacing in engineering applications. The case study of the Jinzhonghe Avenue South Side Plot in Tianjin serves as a practical testament to the ARPW system's efficacy, illustrating its ability to comply with stringent deformation requirements while reducing costs and offering a viable alternative to traditional support methods. This study provides valuable insights into the performance of the ARPW system under controlled conditions. However, it is important to note that our analysis does not account for groundwater-related phenomena, such as seepage and gushing, which are critical in practical applications. These phenomena can exacerbate both local and overall damage to the excavation, potentially leading to inaccurate predictions of actual field conditions. Future work should address these limitations to enhance the applicability of the proposed ARPW system in real-world scenarios.