In order to study the impact of groundwater on slope with planar failure surface

three common forms of water pressure distribution are generalized; and the rationality of assumption for water pressure is described. According to the limit equilibrium theory

using Matlab to program

and through two examples with or without tension fissures

combined the methods of quantitative and qualitative analysis

sensitivities of the factors such as water depth

failure surface angle in sliding surface

slope height

slope crest angle

horizontal angle of tension fissure are analyzed. Dynamic law of influence of the factors on slope safety factor is discussed under different water pressure distributions. The results show that the critical angle of planar sliding slope could be calculated by program according to limit equilibrium theory; and the variation of critical angle is obtained considering groundwater; 10% of empirical value is the floating range. Influence of factors on slope safety factor is enhanced as the rising of groundwater table. The influence of slope height is significant; but the influences of slope crest angle

horizontal angle of tension fissure

and distance from crest to tension fissure are not obvious.