Many landfill cover system slidings have occurred and small shear strength in the interface between cover components has been evoked as the main reason of the observed failures. However, the poor compaction characteristics and low associated strength of some cover soils suggest that in some instances their can influence the cover sliding instead of interface between components. In this paper, the inclined plane test is used to determine geosynthetics interfaces and compacted soil shear strength in cases where the initial normal stress is small. It will be shown that the poorly compacted cover soil can determine the potential failure surface under some conditions and that an appropriate compaction can increase the angle of shearing resistence and to ensure the soil stability in the cover system.