# Review of the Double-Row Pile Supporting Structure and Its Force and Deformation Characteristics
## 4 Deformation Characteristics of Double-Row Pile Supporting Structures  
In the process of foundation pit excavation, the deformation of the double-row pile structure will run through the whole project. Due to the disharmony between pile displacement and soil deformation, the displacement of the pile body is greater than that of the soil, which leads to the phenomenon of pile-soil separation and further causes the bending and horizontal displacement of the pile end [60; 92]. This section mainly summarizes and analyses the deformation characteristics of the whole double-row pile structure and each component, which can play a certain reference role in how to effectively control the deformation of the foundation pit. [PERSON] et al. [96], [PERSON] et al. [97], and [PERSON] et al. [98] found that double-row pile supporting structures can give better play to their overall rigidity characteristics and have a better deformation control effect than single-row pile supporting structures through comparative analysis. Based on the excavation project of the square in front of Huaian East Station, [PERSON] et al. [99] selected different excavation sequences for different pit locations and found that the excavation sequence from far to near could reduce the surface settlement and reduce the deformation of the foundation pit supporting and retaining structure. However, it is not sufficient to control the horizontal displacement of the foundation pit only using a reasonable excavation sequence, which should be combined with other influencing factors. The specific application effect needs to be further studied [100; 101]. Based on the analysis of practical engineering examples, the deformation and stress of the double-row pile structure in the excavation process can be numerically simulated by using three-dimensional finite element theory to analyze the stress and deformation characteristics of the double-row pile structure [102; 103; 104]. [PERSON] et al. [37], [PERSON] et al. [105], and [PERSON] et al. [106], through numerical simulation tests, concluded that the strain and lateral displacement of piles in the front row were larger than those in the back row. Piles in the front row were mainly subjected to bending deformation, while piles in the back row were subjected to tensile deformation. [PERSON] et al. [107] and [PERSON] et al. [108] concluded that the front pile in the middle of the long side of the foundation pit would bear a larger bending moment and have a larger bending deformation, while the back pile would mainly play the role of uplift. [PERSON] et al. [44] used the \"space-time effect\" to reduce the deformation of the supporting structure in the double-row pile supporting project of a deep foundation pit adjacent to the subway and concluded that the deformation rule of the double-row pile in the supporting process is similar to that of a cantilever pile. Under the influence of pipeline excavation, shifting, and backfilling, the top of the supporting pile will appear deformed and show a sudden change. [PERSON] et al. [109] and [PERSON] et al. [110] further found that when the overall stiffness of the supporting structure is too small, it will cause excessive horizontal deformation as well as pile torsional deformation. The deformation of a double-row pile supporting structure is mainly horizontal, and the deformation of the pile structure accounts for a large proportion. The maximum horizontal displacement usually occurs at the top of the supporting pile, and the horizontal displacement along the deep direction of the pile shows a decreasing trend [35; 111]. [PERSON] et al. [112] studied the influence of different embedment depths of supporting piles on the deformation characteristics of double-row pile support structures and the stability of foundation pits through numerical modeling and other methods.