A method for full three-dimensional kinematic analysis of steep rock walls based on high-resolution point cloud data

Abstract

The predisposition of a slope to generate rockfalls is related to the intensity of rock mass jointing and the geometric arrangement of discontinuities intersecting the rock face. With the increasing use of terrestrial laser scanner (TLS) in rock slope surveying, methods have been proposed to semi-automatically extract the spatial properties of outcropping discontinuities from high-resolution topographic data. The present paper builds upon one of such methods (named DiAna), and extends it to enhance the assessment of rockfall susceptibility over steep rock walls. In particular, a Matlab routine (named DiAna-K) that incorporates a full three-dimensional derivation of kinematic analysis principles is introduced. Kinematic tests for plane, wedge, block toppling, flexural toppling, and free fall failure are formulated by explicitly accounting for the presence of overhanging areas of the rock face as well as varying frictional strengths across different discontinuity sets, planes, or intersections between planes. Results from a test application at an abandoned quarry site highlight the ability of the proposed procedure to provide detailed insights into the kinematic feasibility of structurally controlled instabilities. They also demonstrate the importance of properly defining failure mechanisms over steep (and usually undersampled) topographies in order to derive realistic quantifications of rockfall hazards.