# Review of the Double-Row Pile Supporting Structure and Its Force and Deformation Characteristics
## 4 Deformation Characteristics of Double-Row Pile Supporting Structures
The results showed that the deeper the embedment depth of supporting piles, or the harder the soil or rock in the embedment area of the foundation pit, the higher the stability of the double-row pile support structure and foundation pit. [PERSON] et al. [113] further studied the influence of expansive soil moisture content on the supporting structure of foundation pits through numerical modeling and found that the maximum displacement and bending moment of supporting piles were positively correlated with the moisture content of expansive soil. Moreover, once the moisture content of expansive soil exceeds 24.4%, the maximum displacement and bending moment of supporting piles will significantly increase. In deep foundation pit engineering, deformation control is often the most important factor. [PERSON] et al. [114] also studied the influence of soil properties between the front and back rowsof piles on the displacement of the supporting structure through numerical modeling, and concluded that the improvement of soil between piles within 2-4 m below the top of the supporting piles has little effect on reducing the flexural deformation of the piles. [PERSON] et al. [115] and [PERSON] et al. [116] analyzed the support forms of negative angles and positive angles. The deformation characteristics of the negative-angle double-row pile supporting structure are the same as those of the double-row pile supporting structure in the general position. The deformation characteristics of the front and back piles of the double-row pile supporting structure with a positive angle are the same as those of the negative-angle pile. However, the displacement relationship between the lateral piles of the double-row pile supporting structure with a positive angle is opposite to that of the negative-angle type. The total deformation of the pillar pile at the corner is the largest, and the further away from it, the smaller the deformation. It is a pity that the deformation characteristics of the crown beam and connecting beam were not analyzed in the analysis. According to the statistics, the horizontal deformation characteristic curve of the crown beam of the double-row pile supporting structure is a sinusoidal function [117; 118; 119]. However, with the development of The Times, the excavation area of foundation pit wall protection engineering is constantly expanding, and the size of the crown beam is also constantly increasing, which extends the deformation mode of the new crown beam with curves on both sides and a straight line in the middle. [PERSON] et al. [120] and [PERSON] et al. [121] analyzed the difference in deformation modes between large and small crown beams, and the research showed that the intensity of the \"waveform characteristics\" of crown beams was controlled by the depth of the foundation pit and the expression of \"waveform characteristics\" was affected by its size. The spatially indeterminate structure composed of crown beams, connecting beams, and front and back piles can effectively reduce the horizontal displacement of the pile top. However, the deformation characteristics of crown beams and connecting beams are still in the description stage, and deformation characteristics such as ultra-large, ultra-long crowns, and linked beams are still to be explored [122; 123].