# Review of the Double-Row Pile Supporting Structure and Its Force and Deformation Characteristics
## 6 Conclusions and Prospect  
The continuous development of underground space has attracted more attention in terms of the design and construction of foundation pit wall protection engineering. Among them, double-row pile supporting structures are widely used in the infrastructure construction process of wharves, bridges, subways, tunnels, and high-rise and super-high-rise buildings due to their advantages of large stiffness, small lateral stiffness, and no need for internal support [166]. However, the mechanical and deformation characteristics and mechanisms of double-row pile supporting structures are extremely complex, and the mechanical analyses of the pile-soil interaction and corresponding calculation models are constantly optimized; the system is also relatively complex. Therefore, this reviewed and summarized the double-row pile structure, the influence of the soil arch effect on double-row pile-supporting structures, the deformation characteristics of double-row pile-supporting structures, and four aspects of the calculation model of pile-soil interaction. 1. This paper reviewed the research status of double-row pile structures. The influences of structural parameters such as the pile diameter, the pile length, row spacing, pile spacing, and the crown beam size on the performance of double-row pile supporting structures were introduced. It also conducted a comparative analysis of the double-row pile supporting structure under different conditions, such as the combination of long and short piles, whether there were connected beams or not, and different pile layout forms, and then summarized and evaluated the control effect of the double-row pile supporting structure on deformation under different conditions. 2. The mechanism of the soil arching effect was introduced, the relative motion of the soil and pile body and the mechanism of the deformation of double-row pile structures caused by interactions when the soil arching effect occurs was analyzed, and the influence of the soil arching effect and the double soil arching effect on the deformation of row pile structure was reviewed. 3. The research status of the deformation characteristics of the front pile, back pile, connecting beam, and crown beam by numerical simulation and field monitoring was further introduced, and their influencing factors were reviewed. 4. The paper focused on pile-soil force analysis and the calculation model based on classical earth pressure theory, soil arch effect theory, and Winkler theory, summarized the advantages and disadvantages of various calculation models, and put forward our own opinions. The study can provide a reference for the continuous improvement and optimization of the calculation model. The double-row pile supporting structure is a complex spatial integration framework [167; 168], which presents huge challenges for researchers in exploring pile-soil, pile-pile interaction, and deformation. With the development of engineering technology, different forms of double-row pile supporting structures are also being upgraded, such as the newly emerging prefabricated double-row pile supporting structure and multi-row pile supporting structure in recent years, which necessitates higher requirements for researchers in the study of deformation rules and mechanisms of foundation pit supporting structures and the establishment of force analysis and calculation models. Rooted in environmental protection and sustainable development, the new materials used for foundation pit engineering [169; 170; 171; 172] and the construction method based on artificial intelligence are also constantly being updated and iterated [173; 174; 175], which will also promote the development of the industry and greater impetus to reduce carbon emissions. Methodology, Y.W. ; Writing--review and editing, B.L. ; Supervision, W.W. All authors have read and agreed to the published version of the manuscript. This research was funded by the natural science foundation of Shandong Province, China (ZR2021 MD011). Not applicable.