Abstract Rockfalls are one of the major hazards in hilly regions which can impose significant damages to the structures as well as human lives and property. Understanding the behavior of a rockfall along its trajectory is essential in order to design and implement protection measures for providing safe environment. Coefficient of restitution is one of the most important parameters for predicting a rockfall behavior. Back analysis is an effective tool in estimating the coefficient of restitution for a specific area. This study presents the analysis of rockfalls around the Mardin castle by probabilistic methods after estimating the real coefficient of restitution. Run out distance, bounce height, kinetic energy and translation velocity are studied in the area and accordingly barriers in 4m height with capacities ranging from 3000 to 5000 KJ are suggested as protective measures.
1. Introduction Rockfalls are sudden rapid phenomenon with highenergy bearing features in hilly regions which cause significant threats to the environment aswell as human lives and property. A rock fall occurs when rock boulders detach from their original locations on a steep cliff, and travels down-slope (Varnes 1978, Hutchinson 1988). Generally, the detachment of rocks is due to the climatic or biological events causing a change in the forces acting on a rock. The main triggering factors can be pore pressure increases, weathering of the discontinuities, earthquakes, freeze–thaw process, weathering of the rock, root growth and hard winds (Hoek 2007). Once a failure occurs, blocks move downslope following four basic types of motions: free-falling, bouncing, rolling and sliding (Cruden & Varnes 1996). As the controlling parameters change, different types of scenarios may happen in rockfall events. Rockfall kinematics and dynamics depend on the slope topography, block geometry, mechanical properties of the slope forming material and the block such as friction angle, roughness, restitution characteristics and rolling resistances (Alejano et al. 2010). When a rockfall event reveals a threat to people or structures, it is essential to describe the trajectory of the falling rock along a slope in order to design and implement protection measures. The accuracy of the information on boulder velocity, bounce heights, kinetic energies as well as run out distance are the major features of a correct design as well as the verification of the protective measures (Volkwein et al. 2011).