Slope instability from ground-water seepage

Previous researchers have treated the magnitude and direction of the seepage vector as independent variables and found that seepage, parallel to the surface, does not result in the minimum stable seepage slope. In the present paper, the magnitude and direction of the seepage vector is shown to be uniquely related at the seepage face, and seepage parallel to the slope results is the minimum stable seepage slope. Slope failures under seepage are found to be progressive, and the stable slope angle depends on the direction of the seepage vector. The effect of seepage direction on static liquefaction is investigated, and the seepage directions that initiate static liquefaction depend on the slope angle and soil-unit weight. Analytical predictions of the minimum stable seepage slope compare favorably with experimental results.