This study investigates the reasons of excessive movements of a group of reinforced-concrete retaining walls with a total length of over 300 meters, constructed in 2000 in Kocaeli, Turkey. The contractor had documented the construction stages in sufficient detail. Evaluation of available documents, field observations and engineering analysis has shown that the factor of safety for the walls was around one. In other words, the walls were slowly failing. Engineering errors on calculation of earth pressures and the use of wrong backfill were identified as the primary reasons. The factor of safety of the failing walls was significantly improved by using the combination treatment of backfill replacement, base enlargement, post-construction shear key enclosure and drainage improvement
