Abstract: The waste soil landfill sites are numerous and widely distributed. Affected by various adverse geological hazards during the operation period, the stability of theses landfill stie vary significantly and some of them might be critical. Among various waste soil sites that with slope stability concerns, the mountain ditch type of landfill site is the most prominent. However, few studies are reported. This paper presents the stability analysis of the Mao’an waste soil landfill site. Based on the site topography survey and subsurface geotechnical investigation results, the three-dimensional numerical models were established with FLAC3D software. The surcharge conditions induced by the debris flow as the results of the strong rainfall are analyzed. The response characteristics of the debris flow in the field area are obtained through the stress and strain variation relation in the numerical simulation results. The results show that the rainfall infiltration and debris flow overflow loading lead to the increase of the surface tensile stress, which leads to a local tensile plastic yield. The potential failure form in the field is the shallow surface sliding due to the tensile failure of trailing edge. The research results can provide a reference for the remediation of the failed landfill site and protection of landfill sites of the same type.

Key words: Mountain Gully, Landfill, Stability Analysis, Debris Flow, Numerical Simulation