Investigating the Susceptibility to Failure of a Rock Cliff by Integrating Structure-from-Motion Analysis and 3D Geomechanical Modelling

Michele Perrotti,Paolo Allasia,Marco Baldo,Danilo Godone,Piernicola Lollino,Nunzio Luciano Fazio

doi:10.3390/rs12233994

Abstract

Multi-temporal UAV and digital photo surveys have been acquired between 2017 and 2020 on a coastal cliff in soft rocks in South-Eastern Italy for hazard assessment and the corresponding point clouds have been processed and compared. The multi-temporal survey results provide indications of a progressive deepening process of erosion and detachment of blocks from the mid-height portion of the cliff, with the upper stiffer rock stratum working provisionally as a shelf against the risk of general collapse. Based on the DEM model obtained, a three-dimensional geomechanical finite element model has been created and analyzed in order to investigate the general stability of the cliff and to detect the rock portions which are more susceptible to failure. Concerning the evolving erosion process, active in the cliff, the photogrammetric analyses and the modeling simulations result in agreement and a proneness to both local and general instabilities has been achieved.

Highlights

The acquisition techniques for accurate surveys of coastal cliffs have rapidly developed in recent years with the advent of the Unmanned Aerial Vehicle (UAV) technology, providing new opportunities mainly for the study of remote or inaccessible areas [1]
The combined use of SfM and UAV technologies has reached a great success for the 3D point cloud model reconstruction [3], providing the potential for reducing significantly the expertise and time required for generating such surface models [4]
The assessment of F19 and F18, reported in picture (b) of Figure 8, confirmed the insights provided by the previous analysis, highlighting only the ongoing erosion process on the block fragments which originated by the main block failure

Summary

Introduction

The acquisition techniques for accurate surveys of coastal cliffs have rapidly developed in recent years with the advent of the Unmanned Aerial Vehicle (UAV) technology, providing new opportunities mainly for the study of remote or inaccessible areas [1]. Powerful advancements in the Structure-from-Motion (SfM) approach, which combines well-established photogrammetric principles (basically, image matching and bundle adjustment) with modern computational methods [2] for estimating three-dimensional structures from two-dimensional image sequences, have been brought to the development of many software for image processing. The combined use of SfM and UAV technologies has reached a great success for the 3D point cloud model reconstruction [3], providing the potential for reducing significantly the expertise and time required for generating such surface models [4]. In [11], the authors summarize the parameters that affect the reliability of the data acquisition process over the marine environment using Unmanned Aerial

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Discussion

Conclusion