Abstract: To analyze the stability of a thick overburden slope under the effect of transient pore pressure, a method for calculating transient pore pressure was developed based on the formation and distribution of transient saturated area. A modification on Bishop limited equilibrium method was made with the consideration of the influence of transient pore pressure on stability, and a routine using VB was programmed. The proposed procedure was employed to analyze stability of an overburden slope along Ru-Chen expressway in two calculation conditions whether the transient water pressure was considered or not. The results show that the greater the thickness of transient saturated zone, the smaller the safety factor of slope. The lower safety factor exists in slope affected by transient water pressure under the same thickness of transient saturated zone. With the expansion of transient saturation zone, the decrease rate of slope safety factor keeps increasing, up to 39.79%. The potential sliding surface will be tangent to the wetting front and becomes deeper if the thickness of transient saturated area is over 4 meters.

Key words: transient saturated slope, improved Bishop method, transient water pressure, overburden slope