| The rainfall is one of the major factors causing the unsaturated soil roadbed slope failure in The Beijing—Kowloon Railway Line. This is related to the change of water content in soil. If the water content is changed, the shear strength of the soil body will be reduced, which will affect the stability of the roadbed slope.In order to solve the problem of slope stability under rainfall infiltration, this paper presents a finite element analysis model of unsaturated soil which considers hydraulic conductivity curve and soil—water characteristic curve by using SEEP/W module in Geostudio 2004. In this model, the main variable is moisture ratio. The moisture ratio under different raining condintion is calculated. So, using the SLOPE/W module in Geostudio 2004, the slope stability coefficient of the unsaturated soil can be calculated basing on Bishop Equilibrium balance method , Janbu Equilibrium balance method and Spencer Equilibrium balance method etc.The mian conclusion is as follows: when the designed slope stability coefficient is one, the rain fall more strongly,the slope stability coefficient drop more quickly, the raining time is longer, the stability is smaller. But the stability coefficient fall more slowly when the first moisture ratio is higher. Changes in slope stability lag behind the change of weather; Infiltration affect the stability of shallow slip surface greatly, the stability of deep slip surface relatively little; In the process of rain, the critical slip surface changes from deep surface to relative shallow surface. |
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