# Dynamic Stability Finite Difference Time Domain Analysis of Landfill Based on Hypergravity Test
## 6 Conclusions  
Based on the results of centrifuge tests, the FDM nonlinear dynamic analysis method was used to analyze the seismic response of landfills under different water levels and seismic intensities. Utilizing state data stored during the seismic modeling process of the landfill, time-history curves of the dynamic safety factor for different water levels and seismic intensities were obtained. The numerical modeling results are consistent with the test results and phenomena. The main conclusions are as follows:  
1. The seismic acceleration, pore pressure, and deformation response of the landfill obtained through FDM nonlinear dynamic analysis are consistent with the results of centrifuge tests. The development process of pore pressure and deformation under seismic action matches the acceleration time history;
2. The time history curve of the safety factor obtained based on the seismic response of the landfill is closely related to the dissipation of deformation and excess pore pressure, providing an approach to clearly and effectively assess the seismic stability of landfills. Under low water levels and small earthquake magnitude conditions, the stability of the landfill is good, though the cumulative deformation caused by earthquakes can slightly decrease the safety factor. Under high water levels and high-intensity earthquakes, the safety factor of the landfill may decrease to a critical point;
3. The instability of the landfill during earthquakes lags behind the earthquake loading process, which is related to the development of deformation and pore pressure during earthquakes. In the initial stage of earthquake loading, the safety factor of the landfill slightly increases as negative excess pore pressure accumulates. However, as the accumulated deformation caused by earthquake action weakens the landfill and the rebound of negative excess pore pressure reduces the effective stress, the safety factor  
Figure 10: The dynamic safety factor of a high-water-level landfill is calculated using the strength parameters when the destruction strain is 10% and 20%. gradually decreases. After the dissipation of negative excess pore pressure, the safety factor reaches its minimum value;
4. The parameters of MSW are conservative in terms of the value taken via the 10% strain at failure, leading to landfill instability during strong earthquakes. When the strength parameters are determined based on a 20% strain at failure, the stability of the high-water-level landfills is good under seismic intensities of Level III, but instability still occurs under maximum seismic intensity;
5. The strength parameters of MSW directly affect the seismic stability of high-water-level landfills. When the strength parameters are determined based on 10% and 20% strain at failure, instability occurs in high-water-level landfills under maximum Level I seismic intensity. This differs from observations made in centrifugal model experiments. Further research is needed to determine strength parameter values in the dynamic response analysis of solid waste;
6. Factors that affect the difference between centrifuge test results and FDM nonlinear analysis results include assumptions, boundary conditions, parameter values in numerical calculations, and experimental factors such as loading, operation, and equipment, which have not been explored. L.S. : supervision, writing--review and editing. J.L. : conceptualization, methodology, formal analysis, writing--original draft. H.L. : supervision, writing--review and editing. All authors have read and agreed to the published version of the manuscript. This work presented in this paper was jointly supported by the Basic Public Welfare Research Program of Zhejiang Province (Grant No. LGF21E080013) and the Basic Science Center Program for Multiphase Media Evolution in Hypergravity of the National Natural Science Foundation of China (Grant No. 51988101). Data Availability Statement: Data can be acquired upon reasonable request.