Evaluation of rock excavatability and slope stability along a segment of motorway,Pozanti, Turkey

The Çiftehan-Pozant segment of the Ankara-Pozant motorway is problematic due to the existence of lithological units with variable character. Seven cut slopes are planned along Km 358+000– Km 364+350 of the proposed motorway. The purpose of this study is to determine engineering geological properties of the rocks exposed along the motorway and to assess the excavatability and stability of the cut slopes. Both field and laboratory studies were carried out during this study. Field studies involved geological mapping, detailed discontinuity surveying and sampling. Laboratory tests were carried out to determine unit weight, point load strength index and shear strength parameters of the discontinuities. In the study area, recrystallized limestone, microgabbro, conglomerate and Quaternary deposits are exposed. However, the cut slopes are located within microgabbro and conglomerate. Hard to very hard ripping with local blasting for the fresh inner part of the rocks is recommended for the excavatability. In two cut slopes wedge failure is expected, whereas in another two slopes both wedge and toppling failures are likely to occur. Based on the field observations and stability analyses of the cut slopes, slope flattening with various angles, wire mesh, and drainage ditches are proposed.