A New Framework for Geometrical Investigation and Stability Analysis of High-Position Concealed Dangerous Rock Blocks

The rock slopes along the Sichuan–Tibet railway are characterized by noncontactless, inaccessible, dramatically fluctuating topography and large-scale areas. Numerous high-position, concealed dangerous rock blocks (HPCDRBs) are located on such slopes, potentially threatening the construction and safety operation of the Sichuan–Tibet railway. To this end, a new framework is proposed for geometrical investigation and stability analysis of HPCDRBs. The main steps of the framework are: (1) establishment of a three-dimensional high-resolution rock surface model using a new unmanned aerial vehicle-based photography method; (2) identification of possible HPCDRBs based on the theory of structure-controlled rock mass; (3) geometrical characterization of possible HPCDRBs utilizing polyhedral models; and (4) application of block theory for the stability analysis of possible HPCDRBs. In this framework, the actual positions and geometric information of these blocks are well-reflected, and the obtained parameters can directly serve the stability analysis. The proposed method is applied to an ultrahigh-steep rock slope located on the left bank of the Kang Yu Qu (KYQ) Bridge of the Sichuan–Tibet railway. A total of 40 HPCDRBs with volumes between 2.1 and 148.2 m 3 are determined, and the geometric shapes are mainly hexahedron and heptahedron. The mean sliding orientation of these blocks is 124.6°∠51.4°. A seismic stability analysis is finally conducted to further discuss the stability of the HPCDRBs under a real earthquake. In summary, the collapse of the unstable HPCDRBs may cause single block falls which pose a potential threat to the KYQ Bridge.