# Lateral Dynamic Response of Helical Pile in Viscoelastic Foundation Considering Shear Deformation
## 1 Introduction  
The helical pile is a new type of variable cross-section pile foundation, whose side surface is attached by helixes to enhance the interaction between the pile body and soil [1, 2, 3]. The existence of helixes can raise the lateral friction resistance of helical piles, leading to their increasingly widespread application in engineering, especially for some structures that mainly undergo lateral loads such as wave load, wind load, and seismic load [4, 5, 6]. Therefore, in recent years, many scholars have paid attention to investigating the static and dynamic characteristics of helical piles due to their bearing advantages [7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]. At present, many scholars mainly utilize model tests, field tests, and theoretical research methods to investigate the vertical deformation mechanism of helical piles. In the field of the vertical uplift bearing characteristics of helical piles, [PERSON] et al. [19] conducted in-depth research on the transfer mechanism of pull-out load among the helixes, pile body, and soil by considering the size effect of the helixes. [PERSON] et al. [20] obtained the distribution law of soil pressure on the side of a helical pile with a helix at its bottom under the condition of uplift. [PERSON] et al. [21] conducted a comprehensive comparison of the freeze-pull characteristics of helical piles and cylindrical piles in cold soil areas, confirming that helical piles can reduce the freeze-pull disease of foundations in cold regions. [PERSON] et al. [22] studied the interaction between the helixes of the multi-helix helical pile and its influenceon the vertical uplift bearing capacity of the helical pile. [PERSON] et al. [23] studied the influence of pile formation effect on the vertical uplift bearing capacity of the single-helix helical pile, and obtained the corresponding calculation formula of vertical uplift bearing capacity. [PERSON] and [PERSON] [24] studied the uplift performance of the grouting helical pile in residual soil. [PERSON] et al. [25] investigated the vertical uplift bearing capacity of the micro helical pile in different soil layers under different loading modes through on-site experiments. In terms of the vertical compressive bearing characteristics of the helical pile, [PERSON] et al. [26] and [PERSON] et al. [27] successively carried out systematic model tests on the vertical compressive bearing characteristics of helical piles in sand and soft clay. Furthermore, [PERSON] et al. [28] carried out systemic model tests to study the influence of design parameters of the helical pile on its vertical compressive bearing capacity and obtained the reasonable combined design parameters of the helical pile. Through model tests, [PERSON] et al. [29], [PERSON] et al. [30; 31], [PERSON] et al. [32], and [PERSON] et al. [33] successively investigated the calculation theory of the vertical compressive bearing characteristics of the helical pile under different loading conditions and different soil properties, and obtained a series of useful calculation formulas. According to the above literature review, the research on the vertical deformation mechanism of the helical pile has been extensive and in-depth, but there are still relatively few existing research results on the lateral bearing characteristics of the helical pile. However, [PERSON] et al. [34] found that the existence of helixes would improve the lateral bearing capacity of the helical pile through a series of model tests. [PERSON] and [PERSON] [9] as well as [PERSON] et al. [35] also confirmed that the presence of helixes could improve the seismic resistance of the helical pile through large-scale shaking table tests. Meanwhile, [PERSON] et al. [36] derived a calculation formula for the lateral vibration characteristic of the helical pile by the equivalent stiffness method, and once again demonstrated that the changes in the pile parameters of the helical pile have a significant influence on its lateral vibration characteristics.