Assessment of rock slope stability for a segment of the Ankara–Pozantı motorway, Turkey

Abstract

The Çiftehan–Pozantı segment of the Ankara–Pozantı motorway is problematic due to the existence of lithological units with variable characters. Ten cut slopes are planned along Km 352+350–Km 358+000 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 excavatability and stability of the cut slopes. Both field and laboratory studies were carried out during this research. Field studies involved detailed discontinuity surveys. 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, dolomite–limestone, microgabbro, reefal limestone, conglomerate and Quaternary deposits are exposed. However, the cut slopes are located within microgabbro, reefal limestone, dolomite–limestone and recrystallized limestone. Hard to extremely hard ripping with local blasting for the fresh inner part of the rocks is recommended for the excavatability. In eight cut slopes, wedge failure is expected. Based on the field observations and stability analyses of the cut slopes, slope flattening with various angles, wire mesh and drainage ditches are suggested.