1. Geological-Geotechnical Survey Engineer, District of State of Highways, Technical Research Dept., 34000 Kucukyali-Istanbul, Turkey.
2. Research Assistant, Dept. of Geological Engineering, Middle East Technical Univ., 06531 Ankara, Turkey.
3. Professor, Dept. of Geological Engineering, Middle East Technical Univ., 06531 Ankara, Turkey (corresponding author).