This study investigates the failure characteristics of reinforced and unreinforced soil retaining structures backfilled with low quality fill material. Reduced scale model retaining structures reinforced with geotextile simulants were constructed on the firm and rigid foundations and then were exposed to an artificial gravity resulted from geotechnical centrifuge. The retaining structures are vertical walls, sloping walls,steep slopes and embankments with slope angles of 45°.By placing the models in an artificially increased gravitational field, however, to increase the self-weight of the soils, the streesses can be made equal at geometrically corresponding points in the models and the full-scale prototypes. The results indicate an overall better performance for models on compacted clay foundations compared with the cases of unyielding rigid foundations in terms of prototype equivalent heights and relative improvements. On the other hand, the rigid foundations pushed the failure surfaces back from the faces of the walls and slopes. Stability analyses incorporating the horizontal effect of reinforcement were found to be in good agreement with the experimental results.