GIS-based determination of rock slope instabilities on Torul-Kürtün (Gümüşhane) highway and 2-d rockfall modelling

The Torul-Kürtün-Tirebolu road is an alternative route for access between the Black Sea Region and the Eastern Anatolia Region, and has a high traffic potential. However, especially in the part of the route between Torul and Kürtün, rockfall events that occur frequently in almost every season may cause loss of life and property from time to time and interfere with the transportation as it is more frequently encountered. For this reason, the part of the route, which has a higher rockfall potential and poses a threat to rockfalls in this aspect, has been identified as the study area. In this study the potential rockfall mechanism in Torul-Kürtün (Gümüşhane) highway, the spreading distance of falling blocks, the bounce height of the tumbling rocks along the slope face, the total kinetic energies of the tumbling rock blocks were evaluated and the barrier applications and the possibility of preventing the possible blocks to fall were examined. In order to determine the rockfall mechanism in the study area, discontinuity orientation measurements taken from the Sarıosman Monzogranite and dacites of Kızılkaya Formations were evaluated by kinematic analysis method and the mechanisms of instability were defined. According to the susceptibility (instability) map produced for the planar, wedge and toppling type failures, the probability of toppling failure in the study area is higher than the planar and wedge type failures. In the study area, the probability of toppling type failure was found in 127 different locations and approximately 81133 m2 area, while wedge type failure was determined as 4762 m2 in 43 locations and 5 different locations and 2233 m2 for the probability of planar type failure. The cross-sectional lines determined on the slopes to the north of the Torul-Kürtün road route, where the dacites of the Sarıosman Monzogranite and Kızılkaya Formation are spread, were analyzed in the RocFall 4.0 computer program and the kinetic energies of the rock blocks, bounce heights of the tumbling rocks along the slope surface and the horizontal location of rock and points were determined. As a result of the analyses the rock blocks rolling in the sections SH1, SH2, SH3, SH4, SH5, SH6, which were located in the Sarıosman Monzogranite, reached to the road route and the rock blocks in the section analysis SH7 remained on the surface of the slope. In the rockfall analysis of dacites belonging to Kızılkaya Formation, it was determined that rock blocks rolling from all section lines reached to the road route. It was determined that the rock blocks falling to the applied barriers areas in the section lines have been damped. The potential rockfall areas determined in the light of these studies in the Torul-Kürtün road route should be include in the improvement planning as soon as possible by the General Directorate of Highways or AFAD. Keywords: Geographic Information System, Instability maps, Rockfall, Kinematic analysis, Torul-Kürtün hihgway