Pore water pressure and water table in the tension crack will increase gradually under the long duration rainfall with high intensity and it will be adverse to the slope stability. In combination with transient unsaturated seepage calculation

an improved numerical procedure for critical slip field of slope with tension crack under intensive rainfall is proposed. In this procedure

transient pore water pressure field

the location of crack and hydrostatic pressure in crack can be taken into account

put forward under the condition of rainfall has a crack slope critical sliding field numerical simulation method

and its are verified. This procedure has been applied to the stability analysis of a typical clay slope. The results show that: (1) The method can search for any shape of the dangerous slip surfaces under the condition of considering the location of tension crack and hydrostatic pressure in crack; and the safety factor is reliable. (2) Hydrostatic pressure in crack has great influence on slope stability and searching for the sliding surface. (3) Crack location has great influence on slope stability under rainfall; and the closer to the slope shoulder the location of tension crack is

the more unstable the slope is. (4) There is a most disadvantageous depth of tension crack when tension crack is located at the most disadvantageous position.