# Study on Shielding Effect of the Pile Group in a Soft-Soil Foundation
## 1 Introduction  
In regions with deep soft soil, pile group schemes are frequently used to reinforce the foundation of infrastructure in order to control settlement. Hydrostatic piles are widely used in soft soil foundations due to their high strength, efficient construction, and low noise generation [1]. However, the installation of hydrostatic piles generates horizontal additional stress in the surrounding soil, which can easily induce deformation in the adjacent foundation and cause damage to existing structures. As urban land resources become increasingly scarce, many construction projects are conducted in close proximity to residential buildings, railways, and bridge structures, amplifying the issue of disturbance resulting from pile installation. Notably, the deformation control of high-speed railway embankments in soft-soil areas has received significant attention [2]. Given the extremely high speeds of trains, even minor disturbances in the embankment can pose considerable risks [3]. Therefore, research on disturbance control during piling holds great significance for infrastructure development in soft-soil areas. Research on disturbance effects during hydrostatic pile installation has long been a focal point. Some field monitoring studies [4; 5; 6] and model experiments [7; 8; 9] have investigated the disturbance effects from piling on the surrounding soil, but long durations and high costs were required to reach an intuitive and accurate result. In terms of the analytical characterization of piling, researchers first proposed the cavity expansion method (CEM) [10; 11; 12; 13] and the strain path method (SPM) [14; 15] based on extensive theoretical and practical experience. In recent years, numerical simulation techniques have rapidly advanced. Many studies employed finite element methods to simulate the pile installation process using software. Simulations of single-pile installations have achieved promising results, as techniques such as the coupled Eulerian-Lagrangian (CEL) method [16; 17; 18], the arbitrary Lagrangian-Eulerian (ALE) method [19; 20; 21], the material point method (MPM) [22; 23; 24] and the press-replace method (PRM) [25; 26] are efficient at addressing grid distortion issues in pile penetration models. However, when multiple piles are present in the penetration model, computational efficiency tends to decrease [27]. In comparison, the expansion model based on the cavity expansion method has a better simulation effect on pile group installation [28; 29; 30; 31; 32], and is also the method used in this study. The shielding effect is significant for piling sequences and construction technology. Existing studies have pointed out the presence of a \"shielding effect\" during pile installation. [PERSON] et al. (2020) proposed a two-pile analytical model for soil displacement based on the shielding effect [33]. [PERSON] et al. (2021) further investigated the response mechanisms of existing piles and of soil to the neighboring pile installation, and enhanced the analytical model for pile group responses based on the shielding effect [34]. In addressing the shielding effect, some studies have compared the magnitude of disturbance caused by different pile group construction sequences and provided optimized construction approaches for pile groups. [PERSON] et al. [35] and [PERSON] et al. [32] established numerical models for bored piles and CMC piles, respectively, comparing the lateral displacement response of soils under different sequential construction orders, and then they concluded that constructing the pile closest to the disturbance control zone first, followed by piles farther away, resulted in smaller soil disturbances. [PERSON] et al. [36] conducted model experiments to verify the shielding effect of previously installed surrounding piles on subsequently installed center piles, and [PERSON] et al. [37] reached the same conclusion through finite element numerical simulations.