# Numerical Analysis of an Upstream Tailings Dam Subjected to Pond Filling Rates
## 1 Introduction  
This study focuses on the effects of pond filling rates on excess pore water pressure and the stability of an upstream tailings dam. Owing to a low initial investment (as a small amount of building material is required), the upstream method is the most popular design for a raised tailings embankment, especially in low-risk seismic areas [1]. It should be noted that there are over 3500 tailings dams worldwide, of which 50% are of the upstream design [2]. One of challenges in an upstream tailings dam is to ensure the allowable rates of deposition in the pond (i.e., pond filling rates) and still maintain the stability of a tailings dam [3]. This is due to the fact that an upstream tailings dam is constructed by placing dikes on top of previously deposited soft tailings, which could lead to a decrease in dam stability [4] because of the build-up of excess pore water pressure. During the operation of an upstream tailings dam, a small starter dikes is first built at the extreme downstream toe. The dam wall is then progressively raised on the upstream side, mainly founded on the tailings beach. The pond filling operation process is then gradually accomplished as the height of the dam increases during the stage of construction [5, 6]. In general, an adequate pond filling rate allows excess pore water pressure to dissipate gradually during the consolidation process. However, if the consolidation process is not completed when a new dike is built, i.e., in case of high pond filling rates, the excess pore water pressure will not have enough time to dissipate. In this sense, excess pore water pressure could build up under the dikes, which could lead to a critical stability situation of the dam [7]. A close relationship can thereby be seen between the consolidation process and the stability of thedam. In the present study, an approach which can simulate both consolidation processes and stability for a tailings dam is needed. [PERSON] [8] investigated a slow deposition process in impoundments of slimes and tailings based on a nonlinear one-dimensional numerical approach. [PERSON] and [PERSON] [9] used a simple one-dimensional numerical approach for optimizing the allowable rate of deposition on tailings dams. However, due to the complexities of the consolidation process coupled with the stability analysis as well as the complicated behavior of tailings materials, an advanced numerical approach would be appropriate. Note that the actual consolidation in the facility is two-dimensional under the assumption of plane strain or axisymmetric conditions, at least at the straight portions of the tailings impoundments and dams [10]. With regard to the use of the advanced numerical approach for a tailings dam, there have been a number of studies addressing two-dimensional numerical simulations [7; 11; 12; 13; 14; 15] and three-dimensional numerical simulations [16; 17; 18]. In the study by [PERSON] and [PERSON] [12], an investigation on the mechanical behavior and the stability of a tailings dam under static and dynamic loading was performed. Two-dimensional numerical simulations were used in their study for three typical types of tailings dams. [PERSON] et al. [13] developed a numerical model to study the stability of tailings dams subjected to the role of capillarity. Their numerical model considered the consolidation processes under self-weight loads, continuous addition of water with the tailings discharge, infiltration of rainwater, and evaporation. [PERSON] et al. [7; 11] and [PERSON] et al. [15] boosted the two-dimensional finite element method for the simulations of both consolidation processes and the stability of an upstream tailings dam. [PERSON] et al. [7; 11] focused on static aspects, i.e., stability of a curved embankment and strengthening by rockfill embankments, whereas [PERSON] et al. [15] focused on earthquake-induced liquefaction of an upstream tailings dam.