Investigation of rockfall potential of Zonguldak-Kilimli roadway (Turkey)

Rockfall is one of the serious worldwide natural hazards that endangers the safety of life and property. Roads and railroads passing near slopes, and residential areas built at the bottom of the slopes are under threat of rock falling. Rock block falling from the top of the slope with high velocity under the influence of gravity can result in damages to civil structures, disrupting transportation, injuries, and fatalities. This study investigates rockfalls on a roadway passing near the slope with a residential area. Rockfall analyses have been carried out on the Zonguldak-Kilimli roadway based on the field investigations, laboratory studies, and using the two-dimensional Rocfall v.4.0 software. The rock blocks falling in the study area have been observed for 2 years. As a result, a detailed discontinuity survey together with detached and already falling blocks was carried out. The average block size was 34.7 cm and the number of volumetric joints was calculated as 11.2 joints/m 3 . Ten-kilogram, 100-kg, 500-kg, and 1500-kg mass blocks were used in the analysis. The mean of the restitution coefficient (Rn and Rt) values which are the input parameters in the rockfall analysis was chosen as Rn 0.28 ± 0.79 and Rt 0.64 ± 0.11. Some of the falling blocks remain in the road ditch. The other blocks move out of the road ditch and move along the road. According to the results of the analysis, the blocks with a mass of 10 kg move 3.8 m towards the roadway. This situation endangers road safety. The kinetic energies of the blocks depend on their mass. The maximum kinetic energy value of the falling movement blocks was calculated as 160 kJ. The highest restitution value of the blocks that hit the ground is 1.85 m. It was calculated that the height of the restitution was 0.7 m at a distance of 1 m from the slope. Since it is not possible to change the slope geometry, concrete barrier along the roadside is recommended as a preventative measure. The concrete barrier is designed to absorb maximum total kinetic energy of 240 kJ with height of 1.3 m and 1 m ahead of the slope.