Model development for simulating mudslide and the case study of the failure of the gypsum tailings dam in East Texas in 1966

Abstract. Mudslides, avalanches, and mine dam-breaks can be serious disasters and cause severe damages but the detailed flow field description has not been completed yet. This paper developed a modified Bi-viscosity model (MBM) to solve the mudslide flow by adopting Bingham model (BM) and the conventional Bi-viscosity model (CBM). In both CBM and MBM, a yield strain rate is used to identify the plug and liquefied rheological prosperities. In the MBM, an extremely high plug viscosity adopted to represent the stratification effect. BM, CBM, and MBM are integrated into the Splash3D model, which solves Navier-Stokes equations with PLIC-VOF surface-tracking algorithm. The viscosity term is solved by implicit iteration. The model is carefully validated with theoretical results and laboratory data with good agreements. The Splash3D model is then used to study the failure of the gypsum tailings dam in East Texas in 1966, briefed as FGT66. A series of sensitivity analyses on the yield strain rate and grid resolution is performed. The results show that the predicted flood distance and flood speed by MBM is very close to the field data. The MBM results illustrate the process that the plug zone and liquefied zone is developed. The simulations show the initiation of the mudslide flow, the development of the slip surface, the flooding process, and the velocity ceasing process. The slip surface is developed automatically without empirical equations. By comparing the results of BM, CBM, and MBM to the field data, we conclude that the liquefied tailings are under the effect of stratification, and the stratification effect is presented in the extremely high plug viscosity in the Splash3D model.