Abstract: Shanghai Laogang Landfill is built over the soft soils, and the shear strength of the soft soild is a key factor in the stability of the landfill. There is a ton-bag type fly ash landfill area built on the landfill, and the characteristics of the ton-bag fly ash are different from traditional waste and paved fly ash, resulting in insufficient understanding of the stability of the soft soil underlying the landfill. Based on the preliminary geological exploration data, the design parameters of the underlying soil layer of the fly ash landfill are estimated. By using the PLAXIS software, a finite element numerical model of the landfill-foundation is established. Considering the consolidation settlement of the soft soil under layered landfill, the strength reduction method is used to estimate the safety factor of the fly ash landfill slope; The effects of the landfill height, the grade of slope, the loading rate, and the filling method on the underlying soft soil layer are evaluated. The feasibility of expanding the capacity of fly ash landfills, and propose design suggestions to ensure the safety and stability of fly ash landfill are presented.

Key words: Fly Ash Landfill, Underlying Foundation, Stability, Numerical Simulation