# Simulation Study on the Installation of Helical Anchors in Sandy Soil Using SPH-FEM
## 1 Introduction  
Helical anchors are composed of a central steel shaft and one or more helical plates welded onto the shaft [1]. Compared to the driving or excavation methods used for traditional pile foundations, the installation process of helical anchors is relatively simple. The helical anchor is screwed into the design burial depth by applying torque and vertical force at the top of the anchor rod using a helical drilling rig [2], as shown in Figure 1. Compared to traditional piles, helical anchors provide several distinct advantages. They enable rapid installation with minimal construction noise, become operational immediately after installation, and are designed for multiple reuses. These features have made helical anchors a preferred foundation option for a range of structures, including coastal wharves, wind power generators, overhead transmission lines, natural gas platforms, and high-rise skyscrapers [3]. With the application of large-diameter helical anchors in the field of marine engineering, the significant pressure and torque required during the installation process have attracted the attention of scholars [4]. A current research focus is on how to ensure the performance of helical anchor foundations while reducing the pressure and torque during the installation process. The installation of helical anchor foundations is mainly controlled by the advancement ratio (\(AR\)), which is defined as the ratio of the vertical displacement per rotation to the pitch of the helix, as shown in Equation (1), where \(p_{w}\) is the pitch and \(\Delta z\) is the vertical displacement for one complete rotation. The existing industry standards and guidelines [5, 6] typically recommend an \(AR\) of 1.0, which means advancing one pitch of displacement per rotation. This method of installation is also known as \"pitch matching\"or \"perfect\" installation. The main purpose of \"pitch matching\" installation is to minimize soil disturbance during the installation process. Most of the theoretical formulas [7; 8] for calculating installation force and torque proposed by scholars are also based on \"pitch matching\" installation. \[AR=\frac{\Delta z}{p_{w}} \tag{1}\]  
However, an increasing number of studies indicate that the \(AR\) not only affects the torque and force during the installation process but also influences the bearing capacity of the helical anchor. [PERSON] et al. [9] found through indoor model tests that the vertical resistance and torque during the penetration of helical expansion drilling tools decreased significantly with a reduction in the \(AR\). [PERSON] et al. [10] conducted indoor model tests to study the installation force and installation torque of single-helix anchors under three different \(AR\)s (0.25, 0.50, and 1.00). Their findings indicated that at the lower \(AR\) values, specifically 0.25 and 0.50, the required installation forces and torques were close to each other and significantly lower than those observed at the higher \(AR\) of 1.00. [PERSON] et al. [11] simulated the installation and load-bearing of helical anchors under different \(AR\)s using the Discrete Element Method (DEM), finding that installing helical anchors with a low \(AR\) not only significantly reduces installation force but also increases the anchor's uplift capacity. [PERSON] et al. [3], however, reached different conclusions through indoor model tests, observing a decrease in the uplift capacity of helical anchors installed with a low \(AR\). Current research on \(AR\) is still in its preliminary stages, with no unified conclusions yet, and the impact of \(AR\) on the installation and bearing capacity of helical anchors requires further study. Previous studies on the installation process of helical anchors have predominantly been experimental, with limited numerical modeling efforts. This scarcity is largely due to the substantial soil deformations involved, which challenge traditional mesh-based finite element methods.