Abstract：Based on analyzing rock and earth structure in unconsolidated slopes，the style and intensity of permeability pressure in slopes during regulating water level in the Three Gorges Reservoir are discussed. Due to many unsolved boundary problems in simulating variation of water flow in slope，a new formula for calculating permeability pressure in slope is proposed，by studying on permeability pressure in certain boundary conditions with one-dimensional seepage theory. With this formula variation of phreatic surface and permeability pressure in Beimengou landslide in the Three Gorges Reservoir area，are calculated. The results show this formula is reasonable and effective for certain boundary；and it can provide a basis for appraising the stability condition of slopes and designing control projects.
