# Numerical Simulation of Seepage Surface and Analysis of
## 1 Introduction
[24] performed a transient seepage analysis of tailings dams considering the coupling of stress and seepage fields. [PERSON] [25] et al. showed the influence of a different dry and upstream slope ratio on the seepage and stability of a tailings dam and the longer the length of the dry beach, the lower the phreatic line and the greater the safety factor. The higher the upstream slope ratio, the lower the phreatic line and the greater the safety factor. [PERSON] et al. [26] concluded that the seepage field was an important indicator influencing tailings dam stability. [PERSON] et al. [27] analyzed the seepage field of seepage discharge facilities under normal operation and damage and concluded that the permeability of the starter dam was closely related to the seepage stability of tailings dams. [PERSON] et al. [28; 29] carried out numerical modelling analyses of two different types of tailings dams and concluded that the type of tailing dam and the duration of an earthquake directly affected the maximum displacement value formed on the ground. In another study, it was found that the use of cement and fly ash could improve the volume compressibility coefficient of the tailings, which was beneficial to the stability of tailings dams. [PERSON] et al. [30; 31] carried out numerical simulations and indoor physical modelling experiments when considering the number of factors influencing the seepage pattern of tailings dams under rainfall conditions. [PERSON] et al. [32] investigated the effect of beach width on the stability of tailings dams by three-dimensional seepage modelling. [PERSON] et al. [33] showed that the static and dynamic stability of fine-grained tailings dams in high-seismic areas could conform to the specification by constructing high starter dams and providing adequate seepage drainage facilities. [PERSON] et al. [34] found that higher water levels both lead head at the top dam, lower the bottom at the same time, and result in greater destabilization. [PERSON] et al. [35] studied the seepage characteristics of tailings dams, considering the special case of physical and chemical blockages. [PERSON] et al. [36] conducted a case study on the application of geotextiles in tailings dams, and the results showed that this method was effective for seepage control during construction. [PERSON] et al. [37] proposed a novel drainage system for seepage and stability analyses of tailings dams. This new drainage system could reduce the infiltration line and meet dam stability requirements. The study of tailings seepage failure belongs to a multidisciplinary field, which involves disciplines such as mining, geotechnical, hydrological, geological, seismic, slope, and seepage mechanics [38]. Current research has focused on the model test method and numerical simulation method. The model test method has the unique advantage of accurately depicting dynamic contours in specific projects [39]. However, it has limitations in reflecting the actual behavior of seepage, as it is difficult to determine the mapping relationship between the field and model length scales. Numerical simulation techniques are effective tools for studying seepage analyses of tailings dams, due to their ability to characterize models realistically [40]. In seepage analyses of complex projects such as tailings dams, the traditional method directly uses parameters obtained from tests for calculations; sometimes the test parameters may be biased, making it difficult to accurately reflect the seepage field. This research was performed to simulate a three-dimensional seepage and analyze the stability of a 210 m-high upstream tailings storage facility. In this study, seepage back analyses were carried out using measured phreatic line data to obtain seepage parameters that coincide with on-site seepage. The obtained seepage parameter values were then used as input parameters for numerical simulation to carry out seepage analysis.