Terrestrial laser scanning of rock slope instabilities

Abstract

This manuscript presents a review on the application of a remote sensing technique (terrestrial laser scanning, TLS) to a well-known topic (rock slope characterization and monitoring). Although the number of publications on the use of TLS in rock slope studies has rapidly increased in the last 5-10 years, little effort has been made to review the key developments, establish a code of best practice and unify future research approaches. The acquisition of dense 3D terrain information with high accuracy, high data acquisition speed and increasingly efficient post-processing workflows is helping to better quantify key parameters of rock slope instabilities across spatial and temporal scales ranging from cubic decimetres to millions of cubic metres and from hours to years, respectively. Key insights into the use of TLS in rock slope investigations include: (a) the capability of remotely obtaining the orientation of slope discontinuities, which constitutes a great step forward in rock mechanics; (b) the possibility to monitor rock slopes which allows not only the accurate quantification of rockfall rates across wide areas but also the spatio-temporal modelling of rock slope deformation with an unprecedented level of detail. Studying rock slopes using TLS presents a series of key challenges, from accounting for the fractal character of rock surface to detecting the precursory deformation that may help in the future prediction of rock failures. Further investigation on the development of new algorithms for point cloud filtering, segmentation, feature extraction, deformation tracking and change detection will significantly improve our understanding on how rock slopes behave and evolve. Perspectives include the use of new 3D sensing devices and the adaptation of techniques and methods recently developed in other disciplines as robotics and 3D computer-vision to rock slope instabilities research.

Optimising 4-D surface change detection: an approach for capturing rockfall magnitude–frequency

“…The creation of a representative inventory is also a function of the smallest event size that can be detected and the temporal frequency of monitoring compared to the rate at which such small events occur. Abellán et al (2014) suggested that the spatial resolution of rockfall monitoring should be sufficient to discretise the smallest events in a magnitude-frequency distribution and that the recording frequency should fall below the timescale on which superimposition and coalescence may occur. In practice, defining this timescale a priori is challenging and requires the ability to monitor the rock face over a sustained period in (near) real time.…”

“…In this section we describe the protocol for scan alignment applied to the nearcontinuous dataset. As discussed by Abellán et al (2014), aligning point clouds can be undertaken using common surveyed and modelled targets combined with measured global coordinates (Teza et al, 2007;Olsen et al, 2009), featurebased registration based on the planarity and curvature of surfaces (e.g. Besl and Jain, 1988;Belton and Lichti, 2006;Rabbani et al, 2006), and point-to-point and point-to-surface methods, which use iterative closest point (ICP) alignment to progressively reduce the distance between two clouds (Besl and McKay, 1992;Chen and Medioni, 1992;Zhang, 1994).…”

A new approach for semi-automatic rock mass joints recognition from 3D point clouds

“…in order to enable fast advancement in the application of the sensor in disciplines such 48 as rock mechanics, geotechnics and earth sciences, development of new algorithms is 49 needed (Abellán et al, 2014). 50…”

A Comparison of Simulated Annealing, Genetic Algorithm and Particle Swarm Optimization in Optimal First-Order Design of Indoor TLS Networks

“…Architecture reconstruction (Santagati et al, 2013), heritage documentation and preservation (Fanti et al, 2013); 3. Environmental monitoring and disaster prevention (Abellán et al, 2014). Since the objects to be scanned are either large (e.g., a very tall building) or occluded/self-occluded (e.g., a complex industrial site), a scanning network consisting of multiple scan locations is usually required to provide complete coverage of the object, which is the focus of this paper.…”