Slope stability evaluation and monitoring of a landslide: a case study from NE Turkey

Landslides are quite common natural hazards in the eastern Black Sea region of NE Turkey. Following the heavy rainfall in the Koprulu (Rize) village settlement area, located in this region where the slope debris overlies the agglomerates, a failure occurred. Due to the developed tension cracks and deformations on the ground, houses, tea gardens, and roads were damaged completely. To figure out the causes and mechanism of the sliding and to suggest the precautions, a detailed geotechnical study was carried out. Along the five survey lines, twelve boreholes were drilled with a total depth of 300 meters. Also, the geophysical surveys on ten profiles were conducted and the inclinometer measurements were taken in five boreholes. Undisturbed and disturbed samples were collected and laboratory experiments were performed. Inclinometer measurements indicated that the sliding started in the slope debris and then spread to the agglomeratic bedrock. The slope stability was examined using the limit equilibrium (LE) and finite element (FEM) analysis methods. The results of the slope stability analyses showed that the failure mode is talus slide with composite shape and outputs coincide with the inclinometer monitoring results. Based on the collected data, it is determined that there will be unavoidable engineering problems if no precautions are taken. Because of the negative reasons which make the application of supporting methods meaningless in the study area, it is considered that transferring the residences to a safer place without risk of natural hazards will be economical and reliable.