Abstract
Recent advances in remote sensing techniques and computer algorithms allow accurate, abundant, and high-resolution geometric information retrieval for rock mass characterization from 3D point clouds. The automatic application of the extracted information for local scale rockfall susceptibility assessment, where discontinuities characteristics play a major role in rocky slope stability, requires step by step logical procedures. This paper presents a novel methodology to use the extracted discontinuity set characteristics for a local scale rockfall susceptibility assessment, tailored for Uncrewed Aerial Vehicle (UAV) data acquisition. The method consists of 4 steps: (i) 3D slope model reconstruction using UAV digital photogrammetry, (ii) automatic characterization of discontinuity sets, (iii) slope stability analysis, and (iv) susceptibility assessment using a new Rockfall Susceptibility Index. The proposed method was applied to a road cut rocky slope in a mountainous area of the Samaria National Park, in Crete Island, Greece. Visual validation indicates that the areas of higher and moderate rockfall susceptibility on the 3D model of the rocky slope are adjacent to rockfall source areas marked by the presence of fallen blocks on the foot of the slope. The proposed methodological workflow presents novelties related to the use of point clouds for the estimation of the Rock Quality Designation (RQD) index, the visualization of discontinuity set spacing, the evaluation of the persistence and the Slope Mass Rating (SMR) index, as well as the incorporation of the persistence of overhangs into the rockfall susceptibility assessment and visualization.
Highlights
Moving from regional to local scale, rockfall susceptibility assessment methods variate from the GIS spatial analysis tools (Saroglou 2019) that exploit data layers including lithology and presence of geological faults, slope angle, and intensity of triggering mechanisms towards those based on the analysis of the local geological structure and strength of the rock mass (Andrea et al 2010; Irigaray et al 2003; Yilmaz et al 2012)
This work presents a novel methodology for Rockfall Susceptibility Assessment for 3D slope models in the form of point clouds. It consists of four steps: (i) 3D slope model reconstruction using Uncrewed Aerial Vehicle (UAV) digital photogrammetry, (ii) automatic characterization of discontinuity sets, (iii) slope stability analysis, and (iv) susceptibility assessment using a new Rockfall Susceptibility Index
The proposed approach can be used to refine the identification of potential rockfall source areas and to improve the input for hazard assessment, including rockfall run-out simulations
Summary
The rocky slope mapping and stability has transitioned from two dimensional (Baillifard et al 2003; Irigaray et al 2003; Günther et al 2012; Yilmaz et al 2012) to three dimensional (Abellán et al 2006, 2014, 2016; Gigli et al 2014; Bonilla-Sierra et al 2015; Assali et al 2016; Menegoni et al 2019; Zhang et al 2019b; Buyer et al 2020; Papathanassiou et al 2020). Local rockfall susceptibility assessment commonly takes place through the application of indicators such as the Slope Mass Rating index (SMR) of Romana (1993), which considers the angular relationship between the slope and discontinuities alongside basic rock mass characteristics such as discontinuity spacing, persistence, roughness, aperture, and infilling. These strategies can lead to the detection of potential source areas as points or lines to be used for the rockfall run-out simulation. Using such points or lines as potential rockfall initiation areas, conservative, on the
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