Abstract: Based on the multilayer soil water content equation of VG (Van-Genuchten) model， the governing equation of water content and matrix suction is established， with the slope inclination angle taken into account， and the calculation method of infiltration depth of multilayer soil slope with different permeability coefficient ratios between layers is proposed. One-dimensional and two-dimensional models of multilayer soil are established by Seep/w plate in Geo-Studio software to analyze the formation of saturated stagnant water zone at soil interface during rainfall infiltration and the variation characteristics of multilayer soil slope stability under different rainfall conditions. The correctness of the calculation method is verified. The results show that the volume water content and pore water pressure at the interface of multilayer soil slope change greatly during rainfall. For multilayer soil slope with different permeability of each layer， the larger the ratio of permeability coefficients is， the more the rate of downward dissipation of stagnant water at the interface decreases， the larger the range of pore water pressure at the interface is. The pore water pressure increases sharply after the saturated stagnant water area forms， which leads to the sudden decrease of shear strength of soil and the large-scale reduction of stability coefficient of soil slope. The conclusions provide a reference for the early warning of soil slope under rainfall conditions.

Key words: rainfall infiltration, pore water pressure, saturated stagnant zone, multilayer slope, stability