在经验性降雨阈值和边坡稳定性数值分析两大类研究的基础上，考虑了降雨入渗和非饱和土性质，使用岩土有限元软件Plaxis高级模式对滑坡预警降雨阈值进行研究分析。算例表明，将降雨量在降雨时间范围内分成2段后，得到的边坡稳定性变化与实际情况更接近，重新定义前期降雨为在给定初始条件下引起边坡最危险滑裂面到坡面之间土体吸力分布发生变化的降雨。前期降雨时长与潜在滑裂面最大深度成正比，与饱和渗透系数成反比。将前期降雨量引入到降雨强度—持时曲线中作为第三个空间坐标轴，将该曲线拓展为前期降雨量-降雨强度-持时曲面。通过一基岩型边坡算例展示了阈值曲面的建立方法，并通过与模型试验数据的对比验证了其可靠性。

Based on the research of empirical rainfall threshold and numerical analysis, the landslide early warning rainfall threshold was calculated with advanced model of FEM code Plaxis, considering the rainfall infiltration and the characteristics of unsaturated soil. The influence of rainfall distribution mode was firstly studied. The results show that separating rainfall into two phases is better than one averaged phase in slope stability calculation. Then, the antecedent rainfall is redefined with explicit physical significance as the rainfall causes the change of matric suction of the unsaturated soil within the slope surface and the potential slip surface. And the antecedent rainfall duration is directly proportional to maximum depth of potential slip surface and inversely proportional to the saturated permeability coefficient of the soil. The two parameters in the expression of the duration are investigated and the suggested values are given. Lastly, the amount of antecedent rainfall is introduced to the I-D curve as the third coordinate axis to develop A-I-D rainfall threshold surface. A case study of slope on bed rock is carried out to demonstrate the process for establishing this space curve, which is compared with the test data. This verification proves the reliability of the method proposed.