# Review of the Double-Row Pile Supporting Structure and Its Force and Deformation Characteristics
## 1 Introduction
[45] found in their study on the connected beams of a double-row pile supporting structure that properly increasing the stiffness of the connected beams can play a certain control role in reducing the horizontal displacement of the supporting structure. However, when the stiffness increases, there is a node, and when the node is exceeded, the deformation control effect of the connecting beam on the double-row pile structure is no longer obvious, which provides a certain reference for the selection of the design parameters of the double-row pile members. In the process of foundation pit excavation, it must be accompanied by the release, transfer, and balance of soil stress, which is the direct cause of the deformation of the retaining wall structure [46; 47]. [PERSON] et al. [31] and [PERSON] et al. [36] believed that this transmission of stress will inevitably lead to a relative shift between the earth and the pile and continues to expand outward, which causes the double-row pile supporting structure to bear the direct soil pressure and the indirect soil pressure transmitted by soil between piles. The supporting pile is deformed under the combined action of these two earth pressures. To study the development process and deformation law of double-row pile supporting structures, many scholars have used centrifugal testing machines to carry out centrifugal simulation tests and other methods to carry out deformation coordination-related research, gradually carried out a theoretical analysis of force deformation of double-row pile supporting structures, and optimized the related pile-soil calculation model [48]. In terms of theoretical analysis and calculation, the pile-soil calculation model is mainly based on classical earth pressure theory, earth arch effect theory, and Winkler theory [49; 50; 51]. Among the three calculation theories, the Winkler model can easily consider the change in foundation reaction, so the elastic foundation beam method based on the Winkler assumption has been the most widely used [52]. In the Winkler model, the double-row pile supporting structure is approximately assumed to be a vertically placed elastic foundation beam embedded in the soil, the earth pressure and other constraints are assumed to be equivalent springs, and the rod system finite element method is used to calculate the deformation and internal force. However, for example, how the soil shear effect is reflected in the equivalent spring stiffness coefficient \(k\) and the influence of the spatial effect of the connected beam and crown beam on the double-row pile support system still need to be further studied [53, 54]. The above work specifically includes the following research directions: (1) study of double-row pile structure; (2) the influence of the soil arch effect on the double-row pile supporting structure; (3) deformation characteristics of double-row pile supporting structures; (4) the calculation model of pile-soil interaction. This article will be systematically sorted and summarized from the above four directions, with a focus on reviewing and commenting on the current research methods and conclusions on the mechanical deformation characteristics and pile-soil interaction calculation model of double-row pile supporting structures. Finally, the opportunities and challenges facing research on double-row pile supporting structures are described, and the application prospect and development trend of double-row pile supporting structures are forecasted.