# Numerical Analysis of the Installation Process of Screw Piles Based on the FEM-SPH Coupling Method
## 5 Conclusions  
In this paper, a FEM-SPH coupling model was developed to analyze the large deformation problem caused by the installation of a screw pile. The screw pile was modelled using the finite element method and the soil model was built using the SPH method; the installation process of the screw pile is well simulated. Further, the FEM-SPH simulation results were compared with the field tests' results and traditional finite element simulation result. In addition, based on the established FEM-SPH numerical model, the differences in different screw piles were analyzed during the installation process. Based on the analyses conducted in this paper, the following conclusions can be obtained:  
1. By comparing with the experimental results, the accuracy of the FEM-SPH coupling model is verified. FEM-SPH simulation results show a better agreement with the experimental results in terms of the installation torque and the soil deformation of the ground surface, indicating that the FEM-SPH method has good applicability in dealing with the large deformation caused by the installation of the screw pile.
2. Compared to the traditional FE (AIE) method, the FEM-SPH method possesses better efficiency and accuracy at the same time, which is more suitable for simulating the large deformation problem caused by the installation of the screw pile.
3. The FEM-SPH numerical model was used to analyze the installation process of the screw pile. The numerical results show that the interaction during the installation process between the screw pile and the surrounding soil is transferable, and the load transfer occurs throughout the installation of the screw pile. With the increase in the installation depth, the extent of damage to the soil caused by the screw pile will decrease. The installation of the screw pile results in heave damage to the shallow soil and exhibits cylindrical shear damage to the middle and deeper layers.
4. Based on the developed numerical model, the variability in the installation process of different screw piles was analyzed. The analysis shows that the two failure mechanisms (HFM and CSFM) have different effects on the soil during the installation of the screw pile. For HFM and CSFM caused by the installation of the screw pile, the influence range on the soil around the pile of HFM is only related to the pile diameter and is irrelevant to the spiral pitch. Unlike HFM, the influence range on the soil around the pile of CSFM is affected by the variations in both spiral pitch and pile diameter.  
Conceptualization, Q.Z.; Writing--original draft, Q.Z.; Formal analysis, Q.Z.; validation, Q.Z.; Project administration, Y.W. and Y.T.; Writing--review and editing, Q.Z. and Y.W.; Supervision, Y.W. and Y.T.; Data curation, Y.W. and Y.T.; Investigation G.R. and Z.Q.; Visualization Z.Q. and W.L.; Software, Z.Y. and W.L. All authors have read and agreed to the published version of the manuscript. The authors highly appreciate the financial support of this study by Guangdong Water Conservancy Science and Technology Innovation Fund project (No. 2017-31).