Abstract: Finite element method often brings about errors in the calculation of uplift pressure. In view of this,two action modes of uplift pressure in the analysis of the deep sliding stability of double inclined planes were compared and analyzed. Then the methods of applying uplift pressure when analyzing the sliding stability of double inclined planes and gravity dam’s foundation planes using finite element method were researched. It’s found that uplift pressure,as surface load acting on the slip surface or as body load acting on the sliding block,though with approximately equal total force,doesn’t necessarily cause similar effect quantity (displacement and stress,etc) because sliding block is the deformation body. The difference caused by applying surface load or body load in the vertical direction is larger than that in the horizontal direction.

Key words: uplift pressure, gravity dam, FEM, dam foundation surface, double inclined planes