# Slope Failure of Noncohesive Media Modelled with the Combined Finite-Discrete Element Method
## 5 Concluding Remarks  
In this paper, the slope failure behaviour of noncohesive media under gravity and earthquake excitation is investigated using the two-dimensional combined finite-discrete element method (FDEM). Basic aspects of the FDEM are addressed, and two examples are presented for comparison and validation.  
In example I, gravity is applied to a rectangular noncohesive soil heap. The soil heap is half bounded by a steel frame and consequently, the free vertical surface will fail naturally under gravity. The FDEM results are compared with data from SPH simulation, and good agreement is reached. Failure mode, repose angle and slope distance from the FDEM modelling agree quite well with those from SPH simulation.  
In example II, the Chiu-fen-erh-shan landslide induced by the Chi-Chi earthquake is studied using the FDEM. Noncohesive rock blocks are defined and the mountain is subjected to ground excitations. In the FDEM modelling, the mass flow of rock blocks is formed and the movement along the slope surface is recorded. By comparing the failure mode and horizontal travelling distance of the toe block with those from the DEM and MPM, it can be concluded that good agreement is reached. The FDEM is capable of simulating landslide behaviour of noncohesive rock blocks under earthquake.  
It should be noted that there are some differences between the results from the FDEM and results from existing literature in both examples. A clear sliding surface is observed in FDEM simulation in example I, while it is not available in SPH simulation, suggesting that the capability of particle movement in SPH simulation is larger. In example II, the finally formed slope surface by the FDEM is closer to the on-site record. These characteristics are rooted in the natural merits of the FDEM, showing that the FDEM has advantages over other computational tools in modelling slope failure behaviour of noncohesive media under both static and dynamic loads.  
Although this paper is based on 2D and may have some limitations for extending obtained results to 3D, it provides a new insight into the slope failure behaviour of noncohesive media using a novel computational approach, that is, the FDEM. By validation, the FDEM is proven to be applicable and reliable in modelling the slope failure of noncohesive media under both gravity and ground motions. Relevant three-dimensional modelling is under development and will be discussed in another article.  
[PERSON] contributed to the methodology, investigation, validation, writing and review of the original draft. [PERSON] contributed to the analysis, review and edit of the manuscript.  
This research was funded by National Natural Science Foundation of China (Grant No. 51808368), Suzhou University of Science and Technology Natural Science Research Fund (Grant No. XKQ2017008) and Key Laboratory of Structural Engineering of Jiangsu Province (Grant No. ZD1704).  
The authors appreciate the support on the FDEM program 'Y' from Professor [PERSON].  
The authors declare no conflict of interest.  
Figure 12: Time history of the velocity of the toe block.