Geotechnical assessment of a slope stability problem in the Citlakkale residential area (Giresun, NE Turkey)

Because of the rapidly growing population, new settlement areas are required, and finding an appropriate location is always difficult, especially in mountainous areas. In these regions, efficient use of the existing settlement areas or rehabilitating unsuitable areas for settlement is the most common application. The Citlakkale (Giresun-NE Turkey) District residential area, located on a steep slope where debris crops out, was selected as an application site for this study. Following the slope excavation to establish a new settlement in the study area, an instability problem occurred. In order to investigate the causes and mechanism of the failure and to determine the remedial measures, detailed geotechnical studies were performed. Inclinometer measurements revealed that it is a composite sliding with a very slow velocity. Stability of the slope debris was investigated using limit equilibrium (LE) and the finite element method-based shear strength reduction (FEM-SSR) analyses in three stages. These were slope stability analyses for pre- and post-excavation cases and possible remedial measures. According to the stability analyses, the slope excavation was found to be major factor in the occurrence of the failure. Based on the gathered data, retaining wall having a lateral active force higher than 9524 kN was considered to be economical and practical solution as a remediation method. Furthermore, integrating the LE and FEM-SSR methods give useful and reasonably reliable results in assessing the stability of soil slopes.