Assessment of cut slope stability in western Black Sea Region (Turkey)

Özköse, Merve
Cut slopes are intensely prone to weathering in the cause of excavation effects. Weathering effects can reduce strength of rocks and results in instabilities in the long run. By the reasons of rocks containing joints, fractures, faults, bedding planes and pore spaces, they are likely to be weathered because of wetting-drying cycles, climate changes, and chemical action of solutions absorbed. This study is mainly concerned with the slope stability analysis for sixteen permanent cut slopes that are composed of limestone, sandstone, marl and mudstone, having heights between 8 and 60 m, along the highways within the borders of Karabük, Zonguldak and Düzce province at Western Black Sea Region in Turkey. Stability analyses were conducted by considering weathering effects with the help of field works, laboratory tests and computer softwares. The purpose is to reveal instability possibilities occurring throughout the determined slopes, chances that the road cuts may move downslope, and the most vulnerable slopes. Within the scope of this thesis, literature researches, field studies, laboratory works, and stability analyses were conducted. Field studies were performed in order to investigate the rock types that were encountered at the studied road cuts. Field observations about weathering degree and excavation types of the road-cuts have been done to examine their effects on stability, geometry and geological characteristics of the studied cut slopes. Scan line surveys were carried out with the aim of obtaining discontinuity-related data of the road-cuts. As an in-situ test, Schmidt hammer rebound test was carried out in the field to assess the strength of the rock units. Laboratory tests as unit weight, point load and uniaxial compression strength (UCS) tests have been performed on the rock specimens that were taken during field works for determining strength parameters and investigating the differences in weathering degrees of the rocks with the tests of methylene blue and slake durability. Slope stability analyses of the road-cuts were performed in accordance with strength parameters values of the rocks as weathered and relatively fresh types. The analyses were performed by modeling surface of the cut slopes as weathered rock with the determined depths and modeling rest of the slope material as relatively fresh. In addition to the slope stability analyses, rockfall analyses were performed in order to investigate the rockfall risks of the studied cut slopes. Taking into account of the studies performed, instability risks were assessed and prevention about drainage channels were recommended as a remedial measure due to surficial failures of the cut slopes.