Abstract: Generally, reliability analyscs of landslide stability under rainfall infiltration only consider the spatial variability of calculated parameters of soil materials, while the influence of non-uniform distribution of initial water is ignored. To solve this problem, the governing equation for Green-Ampt infiltration model with arbitrary distribution of initial water content under different rainfall conditions is derived, and a variable-step compound Simpson method is used to solve the governing equation for exploring the functional relation between wetting front depth and rainfall duration with different spatial distribution of initial water content. Then, the time-varying probability of landslide during the process of rainfall infiltration is calculated using multidimensional normal cumulative distribution function (Mvncdf). Finally, an actual case is used for verification through comparative analysis. The results show that different spatial distribution of initial water content has a significant impact on the time-varying reliability of landslide stability under rainfall conditions. Compared with the uniform and trapezoidal distribution of initial water content, the exponential distribution has the smallest decrease rate of time-varying reliability for landslide stability under the same rainfall condition. The improved model is feasible for arbitrary distribution of initial water content of soil, which is conducive to the universal application of Green-Ampt model in landslide stability evaluation.

Key words: landslide stability, rainfall, improved Green-Ampt model, time-varying reliability