In this paper, some simple equations are developed for determining the Factor of Safety of slopes against planar sliding under a variety of groundwater conditions. The latter include a dry slope (with or without a tension crack), a saturated slope (with or without a tension crack), and partly saturated slopes with conditions of horizontal or bi-linear phreatic surfaces. The simple equations provide a means of rapidly determining Factors of Safety using a pocket calculator in situations where an approximate first estimate is required. The general equation can be used to calculate Factors of Safety for non-linear phreatic surfaces.
- © The Geological Society, London 1979