Integrating rigid body methods with rockfall simulation to evaluate instability along Tegalrejo road, Gunung Kidul, Indonesia

Summary

Abstract

Rockfall along transportation corridors is strongly controlled by slope geometry, discontinuity conditions, block size, surface material properties, and impact energy loss. This study integrates rock mass characterization, RMi-based block volume estimation, restitution coefficient calibration, and rigid body rockfall simulation to evaluate slope instability along Tegalrejo Road, Gunung Kidul, Indonesia. Field mapping, scanline measurements, and laboratory data were used to characterize interbedded tuffaceous sandstone and siltstone slopes. Rock Mass Rating (RMR) values range from 41 to 63, while Geological Strength Index (GSI) values range from 36 to 58, indicating fair to good rock mass quality. Potential block volumes estimated using RMi range from 0.000265 to 0.0588 m³ and were used as rigid body inputs in RocFall3. The calibrated normal restitution coefficients are 0.315 for sandstone and 0.28 for siltstone, producing rebound heights of 4.96 cm and 3.92 cm from an initial drop height of 0.50 m. These values indicate low rebound behavior on weathered and rough slope surfaces. The unprotected simulation shows that several trajectories may reach the road corridor, with maximum kinetic energy, translational velocity, and total runout distance reaching 28.58 kJ, 31.17 m/s, and 332.05 m, respectively. A 6 m flexible rockfall barrier with an energy capacity of 111 kJ is proposed to reduce rockfall propagation toward the road.