Vertical cuts are prone to several types of failure, such as piping, ground heaving and deep seated or base failure. The latter is the subject of this study and probably attracts less attention in comparison with other types of failure. Although it is commonly believed that such a failure is rare in normal conditions; in presence of the seepage flow, deep seated failure is much likely to initiate and advance prior to other types of failure. In this paper, the stability analysis of vertical cuts in granular soils in presence of the seepage flow is studied against the deep failure. To do so, the stability analysis is made by the use of the well-known method of stress characteristics with inclusion of the seepage flow force. This nonuniform flow field renders the stability analysis quite complex. A semi analytical approach, based on complex algebra, is presented to find the flow filed which is accurate and much faster for calculation of the seepage force at arbitrary points in the field. The solution of the flow field is a background solution for the stress field which is to be found to assess the stability.