Abstract: Hydrostatic pressure can trigger the slope instability, especially for slopes with a large number fissures at top. However, the current slope stability analysis practice rarely considers the adverse effects of joint actions of fissures and the hydrostatic pressure. This paper presents the slope stability analysis results using upper bound limit analysis (UAM) and strength reduction methods on the fissured slopes. Slopes with various angles (30°~80°), various internal friction angles (10°~30°) and various amount of hydrostatic pressure in the fissures were analyzed and the factor of the safeties were reported. The results indicate that the hydrostatic pressure in the fissures can results in a large stability reduction in the slope and up to 30% of the reduction was reported. The critical location of the slip plane are similar in all instable slopes. 

Key words: fissures in slope, hydrostatic pressure, strength reduction, factor of safety