Stability Charts for Simple Earth Slopes

Charts are presented for cohesive-frictional soil which give safety factors and details of critical slip circles for depth factors of 1, 1.25, and 1.50 as well as toe circles. The charts are drawn for pore pressure ratios of 0, 0.25, and 0.50 and for slopes up to 45—. A variation of the friction circle method was used to construct the charts. The format of the charts is similar to Janbu's charts so that the need for so much interpolation, extrapolation, and iteration, a characteristic of earlier charts, has been removed. However, Janbu's method for allowing for pore pressure was found to be unacceptable except for small slope angles and low pore pressure ratios. For high slope angles and pore pressure ratios Janbu's method gives safety factors that are too high.