Abstract: The settlement and stability evaluation of the expressway embankment slope have become more and more mature. This paper analyzes the variation of the matrix suction of an expressway embankment slope under the rainfall conditions. The stability of the slope is evaluated by the strength reduction method using ABAQUS finite element software. The results show that: when the total amount of rainfall is the same, the longer the rainfall duration, the greater the infiltration depth of the slope. The longer the rainfall duration is, the deeper the infiltration depth is. When the total rainfall remains the same, the greater the rainfall intensity is, the easier it is to form a transient saturation zone on the surface of the slope. Because the seepage will be hindered by the slope soil, when the rainfall intensity is strong enough, the rainwater has no time to flow down, so it will accumulate in the surface soil, thus forming a transient saturation zone. It is also related to the permeability coefficient of soil. The rainfall can promote the development of slope displacement, which is related to rainfall intensity, rainfall duration and slope gradient. When the rainfall is over, the vertical displacement of the slope will rebound and the horizontal displacement will continue to develop due to the rainfall infiltration; the rainfall has an adverse effect on the stability of the slope, and the more severe the rainfall is, the easier it is to reduce the safety factor of the slope. When the rainfall reaches a certain degree, the slope toe area will first enter the plastic zone, and then develop the sliding surface upward, resulting in the slope instability.

Key words: Finite Element Strength Reduction Method, Expressway, Elope Engineering, Rainfall