Characterization of high and steep slopes and 3D rockfall statistical kinematic analysis for Kangyuqu area, China

Abstract

In the mountainous areas passed by the Sichuan–Tibet Railway, rockfall is one of the important geological hazards with characteristics of unpredictable and sudden occurrences. For high and steep slopes, this study employs nap-of-the-object photogrammetry with the characteristic of close flight distance to reconstruct a 3D geological model, which is clear and qualified for discontinuity identification. For the rockfall investigation of areas where unstable blocks are widely distributed, this study proposes a new methodology for 3D rockfall risk statistical analysis to conduct well-directed rockfall simulations and perform a rockfall analysis on a tunnel portal. This methodology first narrows down the rockfall source regions through a field investigation and by slope aspect. Then, the critical source areas that threaten the tunnel portal are determined by preliminary simulation results. Finally, unstable blocks within the critical source areas are interpreted, and well-directed simulations are performed. The rockfall risk analysis on the tunnel portal is conducted on the basis of trajectory distributions and kinematic parameters. This methodology greatly simplifies the rockfall simulation process and reduces the workload of unstable block identification and interpretation. As a consequence, in the Kangyuqu area, several unstable blocks are identified for simulations. Results indicate that rockfalls reaching the tunnel portal have a kinetic energy range of 300–20,000 kJ, a velocity range of 8–30 m/s, and a maximum jump height of 25 m.