Dynamic Response Characteristics and Liquefaction Analysis of a Phosphogypsum Tailings Dam

Static and dynamic stability analyses are crucial components of engineering practice for ensuring the stability of phosphogypsum (PG) tailings dams. Within this context, the liquefaction analysis under seismic loads plays a pivotal role in ensuring the dynamic stability of PG tailings dams. Under seismic loads, the complicated dynamic response of the tailings dam has a significant effect on the stability of the tailings dam. In this study, considering the support of bedrock on the tailings dam, we perform a three-dimensional (3D) numerical analysis of the Zhuyuan PG tailings dam located in the city of Yichang, China, using FLAC3D. In order to consider the influence of the drainage system on the burial depth of the phreatic line, we consider a complete drainage system in the 3D model, which creates favorable drainage conditions for the tailings in its vicinity. The fully nonlinear numerical analysis method based on the Finn constitutive model and P2PSand model is employed to assess the tailings’ liquefaction potential under seismic loading. We also utilize the built-in FISH language in FLAC3D to judge, track, and label (visualize) current and past liquefaction zones in two groups, Liquefy-n and Liquefy-p, to emphasize the importance of past liquefaction zones for the dynamic stability of tailings dams. The results suggest that the P2PSand model demonstrates a stronger capability than the Finn model in capturing the development of excess pore pressure and the soil liquefaction trend over repeated cycles of loading. The liquefied PG is mainly located in the area below 5 m from the phreatic line, rather than in the area between 0 and 5 m from the phreatic line, where excess pore pressure can be quickly dispersed into the surrounding areas once it reaches the phreatic surface. Additionally, we perform a stability analysis using the strength reduction technique based on the postliquefaction residual shear strength to determine the factor of safety.