Abstract: In traditional methods for slope stability analysis, it is difficult to obtain continuous long time series of soil water content. Using the data series of precipitation, temperature and vegetation coverage in the study area, this paper develops a variable infiltration capacity (VIC) hydrological model for calculating the daily variations in soil water content that is used as a key factor in slope stability analysis. The results show that during 1970-2010, the spatial-temporal distribution of soil water content in the Wei River basin took an increasing trend, and that soil shear strength was decreased but approached a stable level at about 2‰ less. Calculations of the strength reduction method based on the M-C equal-area circle DP3 criterion show that during this period, the slope stability factor k was increased, and its value of larger than 1.2 covers more than 85% of the time period, with only 9% in the range of 1.0-1.2 and 5.5% below 1.0. A R/S analysis on the soil shear strength time series reveals that the Hurst coefficients of the τ-t curve and k-t curve are 0.5568 and 0.5888, respectively, falling in the range of no variation. Based on the calculations, we conclude that the sliding bodies are stable at present and in future, and our VIC method is effective in calculations of soil water content, soil shear strength, and slope stability.

Key words: variable infiltration capacity (VIC) model, soil water content, shear strength, finite element method, R/S analysis