Characterization and monitoring of the Åknes rockslide using terrestrial laser scanning

Abstract

Abstract. Terrestrial laser scanning (TLS) provides highresolution point clouds of the topography and new TLS instruments with ranges exceeding 300 m or even 1000 m are powerful tools for characterizing and monitoring slope movements. This study focuses on the 35 million m 3Å knes rockslide in Western Norway, which is one of the most investigated and monitored rockslides in the world. The TLS point clouds are used for the structural analysis of the steep, inaccessible main scarp of the rockslide, including an assessment of the discontinuity sets and fold axes. TLS acquisitions in 2006, 2007 and 2008 provide information on 3-D displacements for the entire scanned area and are not restricted like conventional survey instruments to single measurement points. The affine transformation matrix between two TLS acquisitions precisely describes the rockslide displacements and enables their separation into translational components, such as the displacement velocity and direction, and rotational components, like toppling. This study shows the ability of TLS to obtain reliable 3-D displacement information over a large, unstable area. Finally, a possible instability model for the upper part ofÅknes rockslide explains the measured translational and rotational displacements by a combination of southward planar sliding along the gneiss foliation, gravitational vertical settlement along the complex, stepped basal sliding surface and northward toppling toward the opened graben structure.

Use of LIDAR in landslide investigations: a review

“…Gravitational features as scarps, trenches and depressions forming the ''Les Pics DSGSD'' could be clearly identified. The real instability extend could be better defined using LIDAR-derived DEM than in aerial photographs or from topographic maps (Data from swisstopo) (Slob and Hack 2004;Jaboyedoff et al 2007;Oppikofer et al 2009;Sturzenegger and Stead 2009;Armesto et al 2009;Lato et al 2009), but still quite rare for ALS-DEM.…”

“…Monitoring surface displacements in rock slopes is, in a way, simpler than in soil slopes because the displacements can be considered as rigid body transformations (Teza et al 2007;Monserrat and Crosetto 2008;Abellan et al 2009;Oppikofer et al 2009). As a consequence, it is easier to identify and decompose the movements as a combination of translations and rotations of different parts of the slope.…”

“…The COLTOP technique (Jaboyedoff et al 2004a(Jaboyedoff et al , 2009b; Derron et al 2005) permits to visualize the orientation of each discontinuity set by a unique colour, which makes the approach very similar to a field data acquisition (COLTOP-3D, www.coltop3d.ch). The extracted data permit to analyse the rock instability mechanisms (Janeras et al 2004;Jaboyedoff et al 2008b;Oppikofer et al 2009). …”

“…Using this algorithm, the differences between points are iteratively reduced by a minimization of a mean square cost function. Alternatively, the alignment over discrete parts of the slope can be carried out using the Roto-Translation technique described by different authors (Teza et al 2007;Monserrat and Crosetto 2008;Oppikofer et al 2009). …”

Terrestrial Remote Sensing techniques to complement conventional geomechanical surveys for the assessment of landslide hazard: The San Leo case study (Italy)

“…Terrestrial remote sensing techniques, including both Terrestrial Laser Scanning (TLS) and Close-Range Photogrammetry (CRP), represent a useful complement to conventional field mapping and rock mass discontinuity characterization [Coggan et al, 2007;Ferrero et al, 2009;Bistacchi et al, 2011;De Souza et al, 2013]. Both these techniques were proven to be useful in the study of rock slopes by several Authors [Bitelli et al, 2004;Abellan et al, 2006;Oppikofer et al, 2009;Sturzenegger et al, 2009a;Jaboyedoff et al, 2010;Nguyen et al, 2011;Giardino et al, 2011;Matasci et al, 2012;Humair et al, 2013;Wolter et al, 2013;Barbarella and Fiani, 2013;Di Salvo and Lo Brutto, 2014]. The comprehension of the main strengths and limitations of the survey techniques (i.e., geomechanical survey, TLS and CRP) permits to understand how they can be complemented to achieve a better characterization of the rock mass.…”