# Review of the Double-Row Pile Supporting Structure and Its Force and Deformation Characteristics
## 3 Influence of the Soil Arch Effect on Double-Row Pile Supporting Structures  
With the excavation of the foundation pit, the soil arch effect is gradually generated and expanded, which is bound to have a certain influence on the stability and supporting effect of the double-row pile supporting structure. This section mainly analyses the relative motion state and interaction between the soil and the pile when the soil arching effect occurs and expands. The deformation mechanism of the double-row pile structure caused by the soil arch effect and the influence of the soil arch effect on the stress and deformation characteristics of the double-row pile supporting structure are reviewed. According to the available data, [PERSON] [88] first named the arch effect phenomenon, which means that the load in the unstable soil will be transmitted to the surrounding rigid boundary. [PERSON] [89] believed that the soil arching effect is a phenomenon of soil shear stress transfer. In the process of foundation pit excavation, the double-row pile supporting structure will produce displacement and flexural deformation in the direction of the pit when it bears the earth pressure generated by the soil mass under the action of dead weight or overload. Then, the relative displacement between the supporting pile and  
Figure 2: Schematic diagram of a plane model with an arched beam. the soil behind the pile will occur, and the soil will also deform due to the shear friction between the soil particles. At this time, the stress of the deformed soil will be released and transferred to the undeformed soil; that is, the earth arch effect occurs, and the collapse area before the arch is formed [90; 91; 92], as shown in Figure 3. [PERSON] et al. [93] and [PERSON] et al. [36] found that the outward expansion of the soil arch effect would make supporting piles bear additional indirect soil pressure transmitted between adjacent piles or even between pile groups based on direct soil action. The superposition of heavy earth pressure will cause the double-row pile supporting structure to continue to produce displacement and deflection in the direction of the pit. Different from single-row pile supporting structures, double-row pile supporting structures will produce a soil arch effect around the front and back piles, and the supporting system will be affected by the superimposed soil arch effect of these two parts. [PERSON] et al. [94] found through research that properly increasing the horizontal pile spacing in rows of piles could reduce the area of multiple soil arches as a whole, thus reducing the stress of the multiple soil arch effect as a whole. However, if the soil arch effect zones of the front pile and the back pile are compared and analyzed, the soil arch effect zone around the back pile is reduced, while the soil arch effect zone of the front pile is increased. At this time, the residual load of the front pile will increase, which is unfavorable to the horizontal bearing performance of the front pile [31; 32; 33]. [PERSON] et al. [95] and [PERSON] et al. [47] considered the double soil arching effect under the influence of the double-row pile support system, and the theoretical calculation value of the earth pressure is closer to the monitoring value of the earth pressure. In foundation pit wall protection engineering, there is soil pressure distribution transfer and balance at every stage of the development of the soil arch effect, which will always accompany the engineering. To simplify the calculation and facilitate analysis, the soil arching effect on a two-dimensional model is usually studied with emphasis; that is, a vertical section is taken out for analysis. However, the three-dimensional effect of soil cannot be ignored. The three-dimensional soil arching effect has a great influence on the supporting effect of the supporting structure [53; 84].