Abstract: In the analysis of the basal heave stability of excavations, the reasonable failure mode and the slip surface are the basis for determining the safety factor. However, there are many different types of basal heave failures. The traditional stability analysis methods and the existing codes have differences and limitations in terms of the failure mode and slip surface. Based on the discontinuity layout optimization method (DLO), the influences of non-homogeneous soil strength and excavation width on the basal heave failure mode are investigated. The results show that the soil inhomogeneity should be considered in the basal heave stability analysis. Furthermore, the influences of the length and bending strength of the retaining piles on the slip surface are analyzed, and the method to distinguish the wide and narrow excavations is proposed. For the wide excavations, when the retaining structures are short, the slip surface is below the toe of the retaining structures, and the slip surface should be adjusted when the circular slip method is used. For the narrow excavations, the slip surface should also be modified to consider that the space effect is benefit for the basal heave stability.