# Dynamic Stability Finite Difference Time Domain Analysis of Landfill Based on Hypergravity Test
## 1 Introduction
Conventional analysis methods for assessing the seismic stability of dams or slopes are not directly applicable to landfills, given their unique characteristics. During earthquake activities, MSW may experience large-scale plastic yielding and plastic flow, which can increase the possibility of landslides or even flow slides in the landfill [11]. Additionally, a composite liner system, installed at the bottom of a landfill, consists of both a drainage system, typically composed of sand, and an anti-seepage system, comprising geotextiles, geomembranes, and clay layers. This composite system plays a vital role in preventing pollution by effectively containing and managing leachate. Nevertheless, it is important to note that the presence of such a liner system makes a landfill prone to sliding along its bottom liner [19]. Pseudo-static analysis has been applied to study the failure of landfills under seismic force [20; 21]. However, the seismic coefficient primarily influences the value of the safety factor, and the dynamic response cannot be obtained when taking this approach. [PERSON] and [PERSON] [15] pointed out significant differences in the dynamic characteristics of MSW and stated that nonlinear analysis methods should be used for the dynamic response analysis of a landfill. In their later work [22], the nonlinear analysis was incorporated into the analysis of seismic stability using [PERSON]'s sliding block analysis. [PERSON]'s method relies on the estimated deformation of a landfill to assess its seismic stability and fails to present the dynamic response of a landfill. Hence, traditional methods such as pseudo-static analysis and [PERSON]'s sliding block analysis are limited in studying the seismic stability of landfills. In recent years, some advanced numerical approaches, such as the finite element method (FEM) and finite difference method (FDM), have been employed to investigate the response and stability of landfills during seismic activities. Using the finite element method, equivalent linear analysis has been applied in many studies to investigate the seismic response of landfills [23; 24; 25; 26]. Yet, the equivalent linear model was considered unsuitable for cases where the acceleration exceeds 0.4 g [27]. [PERSON] and [PERSON] [28] adopted a nonlinear dynamic response analysis and used the ideal elastoplastic constitutive model and Mohr-Coulomb yield criterion to reflect the mechanical characteristics of bedrock and used the modified Cambridge model to reflect the mechanical characteristics of artificial solid waste. Their results obtained in FDM analysis using FLAC software were in good agreement with the measured data, suggesting that nonlinear analysis using the finite difference method could be considered reliable for analyzing the dynamic stability of landfills. Unfortunately, the study neglected to consider pore pressure within landfills, which is a critical factor influencing their dynamic stability. [PERSON] and [PERSON] [29] conducted the finite element analysis to investigate the seismic response of landfills, treating MSW as a mixture of solid and liquid components and considering the nonlinearity of material and contact. In their work, permanent displacement was utilized to assess the seismic stability of landfills. Even though the response of pore pressure within a landfill can be obtained in their study, it did not match well with the data of centrifuge tests. Moreover, the study neglected to build a relationship between the pore pressure response and the seismic stability of landfills. Therefore, improvements are necessary to better depict the seismic response of pore pressure of a landfill and to make the assessment of the seismic stability of landfills clearer and more effective.