Abstract
The main road to the Parangtritis Beach tourism site in the southern Yogyakarta Province, Indonesia, has full of local and economic activities. The road was made mainly by karst mountains cutting and resulting in almost vertical long and high slopes by its side. Rockfall is being the most potential hazards occurred in this area. The purpose of this study is to determine the rockfalls hazard assessment along the main road using Slope Mass Rating (SMR) analysis. Parameters used in rockfall hazard assessment are SMR with additional valuation from the slope height and the block size. The necessary data of each parameter obtained by direct measurement and the uniaxial compressive strength test in the laboratory. Geomechanics analysis, stereographic projection analysis, and hazard parameters weighting are needed to produce research results in form Rockfall Hazard Zonation Map in the research location. The results showed that the largest percentage of rockfalls hazard class is very low class, with 83,83% of the total hazard classes, associated with normal SMR score (51,66 – 51,75), slope height between 2,85 – 4,57 m, and block size 0,2 – 0,3 m. Followed by intermediate class with 7,16% of the total hazard classes with very bad to bad SMR score (5,82 – 38,15), slope height between 4,26 – 8,96 m, and block size 0,3 – 1,0 m. In the third position followed by a low class with 4,28% of the total hazard classes with bad to normal SMR score (31,17 – 53,03), slope height between 3,52 – 5,28 m, and block size 0,2 – 0,7 m. The last position was taken by high class with 4,19% of the total hazard classes with very bad to bad SMR score (18,31 – 36,50), slope height between 3,62 – 7,82 m, and block size 0,7 – 1,3 m. The SMR analysis also identified the influence of rock types with the rockfall occurrence. Hazard zonation map verification showed a congeniality with the results of rockfalls quantity inventory in the research area.
Influence of expertise on rockfall hazard assessment using empirical methods