Engineering geological investigations along the Ilıksu Tunnels, Alanya, southern Turkey

The main objective of this study is to assess the engineering geological characteristics of the rock mass and to suggest appropriate support recommendations along the two autoroad tunnel projects, named as Ilıksu 1 and Ilıksu 2, which are located along the Antalya–Alanya Highway. The study area consists of pelitic schist and calc schist overlain by a thick sequence of recrystallized limestone and an intercalation of pelitic schist, calc schist and graphite schist. The tunnel ground support types and categories were determined according to the Q-system, Rock Mass Rating (RMR) method and New Austrian Tunneling Method (NATM). Slope stability analyses were performed at the portal and cut slope sections. Kinematic and limit equilibrium analyses incorporating the effects of water pressure were performed for the failed rock slopes. Slope stability analyses of irregularly jointed, highly foliated lithologies were performed using soil slope stability software. The interactions of the tunnel support systems with the rock mass were analyzed through finite element analysis.