Cross-Bedding and Structural Mapping for Rockfall Assessment of a Tunnel using Hi-Resolution LiDAR (Fribourg, Switzerland)

2021 ◽  
Author(s):  
Tiggi Choanji ◽  
Charlotte wolff ◽  
Li Fei ◽  
Lidia Loiotine ◽  
Amalia Gutierrez ◽  
...  
Keyword(s):  
Incidence Angle ◽  
Point Clouds ◽  
Surface Geometry ◽  
Rockfall Hazard ◽  
Rock Face ◽  
Sedimentary Structures ◽  
Cross Bedding ◽  
Lithology Identification ◽  
Discontinuity Mapping ◽  
Rock Strata

<p>Lithology identification and discontinuity mapping are necessary for rockfall hazard assessment in tunnels. However, the restricted exposure and variability of rock face orientation in tunnels ought to be taken into account. Therefore, using Light Detection and Ranging (LiDAR) technique may significantly contribute to this task.</p><p>A historical carved tunnel in the Upper Marine Molasse (a poorly consolidated sandstone) of the City of Fribourg (Switzerland) was then investigated by fieldwork and LiDAR. Interestingly, it appears that in addition to joints and layering, some specific sedimentary structures, i.e. cross-bedding, have an important role in the tunnel roof stability. Cross-bedding is a sedimentary structure that can be identified clearly by the geometry of layer within one or more beds in a series of rock strata that does not run parallel to the plane of stratification.</p><p>In order to detect and analyse these sedimentary structures, the intensity of the backscattered LiDAR signal is analysed using the Oren-Nayar reflectance model, which considers range, incidence angle, scanned surface geometry (i.e. roughness). It provides corrected values of intensities that make possible to distinguish and identify geometry of cross-beddings in the tunnel.</p><p>An analysis of structural discontinuities was also performed using Coltop Software which identified joint sets developed inside the tunnel. Based on this approach, lithology characterizations, orientation of each discontinuity and bedding structures could be identified in point clouds confidently for understanding the mechanisms of potential rockfalls in the tunnel.</p>

scholarly journals A storm event during the Maastrichtian in the Cauvery basin, South India

2006 ◽  
pp. 35-40 ◽  
Author(s):  
Mu Ramkumar
Keyword(s):  
South India ◽  
Storm Event ◽  
Environmental Implications ◽  
Cauvery Basin ◽  
Sedimentary Structures ◽  
Cross Bedding ◽  
Depositional Setting ◽  
Cut And Fill

Sedimentary structures in the Kallankurichchi Formation of the Ariyalur Group, South India have been examined with a view of assessing the depositional setting of these rocks. Of the different sedimentary structures such as cross bedding, cut and fill, etc., hummocky cross stratification is significant as it resulted from a major storm event. This paper deals with the recognized sedimentary structures, their genesis and environmental implications.

scholarly journals Temporal-Spatial Frequency Rockfall Data from Open-Pit Highwalls Using a Low-Cost Monitoring System

2020 ◽  
Vol 12 (15) ◽  
pp. 2459
Author(s):  
Anna Giacomini ◽  
Klaus Thoeni ◽  
Marina Santise ◽  
Fabrizio Diotri ◽  
Shaun Booth ◽  
...  
Keyword(s):  
Monitoring System ◽  
Low Cost ◽  
Surface Mining ◽  
Open Pit ◽  
Rock Surface ◽  
Accurate Information ◽  
Stereo Pair ◽  
Mining Operations ◽  
Rockfall Hazard ◽  
Rock Face

In surface mining, rockfall can seriously threaten the safety of personnel located at the base of highwalls and cause serious damage to equipment and machinery. Close-range photogrammetry for the continuous monitoring of rock surfaces represents a valid tool to efficiently assess the potential rockfall hazard and estimate the risk in the affected areas. This work presents an autonomous terrestrial stereo-pair photogrammetric monitoring system developed to observe volumes falling from sub-vertical rock faces located in surface mining environments. The system has the versatility for rapid installation and quick relocation in areas often constrained by accessibility and safety issues and it has the robustness to tolerate the rough environmental conditions typical of mining operations. It allows the collection of synchronised images at different periods with high-sensitivity digital single-lens reflex cameras, producing accurate digital surface models (DSM) of the rock face. Comparisons between successive DSMs can detect detachments and surface movements during defined observation periods. Detailed analysis of the changes in the rock surface, volumes and frequency of the rocks dislodging from the sub-vertical rock surfaces can provide accurate information on event magnitude and return period at very reasonable cost and, therefore, can generate the necessary data for a detailed inventory of the rockfall spatial-temporal occurrence and magnitude. The system was first validated in a trial site, and then applied on a mine site located in NSW (Australia). Results were analysed in terms of multi-temporal data acquired over a period of seven weeks. The excellent detail of the data allowed trends in rockfall event to be correlated to lithology and rainfall events, demonstrating the capability of the system to generate useful data that would otherwise require extended periods of direct observation.

Landslide and Rockfall failures Characterization with Object-Based 3D Analysis

2020 ◽  
Author(s):  
Efstratios Karantanellis ◽  
Vassilios Marinos ◽  
Emmanouel Vassilakis
Keyword(s):  
Spatial Information ◽  
Point Clouds ◽  
3D Models ◽  
Vital Role ◽  
3D Analysis ◽  
Rockfall Hazard ◽  
Area Of Interest ◽  
Object Based ◽  
Great Heterogeneity ◽  
Close Range

<p>Geological failures from massive rockfall failures to small landslides of few cubic meters are a major geological hazard in many parts of the world. Based on the latest developments, close-range photogrammetry and individually UAV photogrammetry and Light Detection and Ranging systems have become indispensable tools for geo-experts in order to provide ultra high-resolution 3D models of the failure site. TLS suffers from the fact that is sometimes tricky to capture the holistic area of interest from the ground, while some areas may often be obscured by vegetation or negative inclinations. The science of photogrammetry has long been used to accurately detect and characterize landslide and rockfall failures. Due to the continuously increasing spatial resolution capability of new generation sensors, traditional pixel-based approaches are not capable to cope with the level of detail resulted from those sensors. Mostly, landslides present complex and dynamic geomorphological features with great heterogeneity in their spatial, spectral and contextual properties dependent on the specific failure mechanism. In the current study, an object-based 3D approach for the automated detection of landslide and rockfall hazard is presented based on detailed topographic photogrammetric point clouds and 3D analysis. Recent trends show that close photogrammetry will play a vital role on the geological and engineering geological assessments concerning geo-failures. The results show that object-based approach is closer to human interception due to integration of contextual and semantic, spectral and spatial information rather than translating pixel’s spectral information solely. The current procedure provides a detailed objective quantification of landslide characteristics and automated semantic landslide modelling of the case site.</p>

The assessment of rockfall hazard at the base of talus slopes

1993 ◽  
Vol 30 (4) ◽  
pp. 620-636 ◽  
Author(s):  
S.G. Evans ◽  
O. Hungr
Keyword(s):  
British Columbia ◽  
Physical Modelling ◽  
Analytical Models ◽  
Lumped Mass ◽  
Mass Model ◽  
Geological Evidence ◽  
Rockfall Hazard ◽  
Rock Face ◽  
Rock Fragments ◽  
Talus Slopes

Fragmental rockfall is characterized by the independent movement of individual rock fragments after detachment from a rock face. The continued operation of the process leads to the accumulation of talus slopes. On talus slopes the rockfall shadow extends beyond the base of the talus and consists of scattered boulders that have run out beyond the base of the slope. The landing probability of boulders in the shadow is examined; return periods of the order of 1000 years relative to a house site are typical. Rockfall behaviour particularly with respect to run out into the shadow can be assessed using geological evidence, empirical methods, physical modelling, and computer-based analytical models. An empirical minimum shadow angle of 27.5° (i.e., the angle between the distal limit of the shadow and the top of the talus slope) is suggested and would be useful in rockfall vulnerability studies at the base of talus slopes as a first approximation to shadow limits. It is preferable to the use of the rockfall fahrböschung as proposed by several authors. A random collision lumped mass model (ROCKFALL) is outlined, ROCKFALL uses two restitution coefficients and a transition to rolling criterion, ROCKFALL is used to analyse two fatal rockfall accidents in southern British Columbia, at Hedley in 1939 and Sunnybrae in 1983, which are documented in detail. An additional nonfatal incident is also analysed (Barnhartvale in 1974). Results based on an initial calibration were encouraging. Documentation of the three rockfall incidents shows that, in each case, rockfall fragments impacted on homes at equivalent shadow angles of 30° or more. This would suggest that a review of existing development within rockfall shadow areas at the base of talus slopes may be in order. Key words : rockfall, dynamics, talus slopes, landslides, British Columbia

scholarly journals GEOMETRIC POINT QUALITY ASSESSMENT FOR THE AUTOMATED, MARKERLESS AND ROBUST REGISTRATION OF UNORDERED TLS POINT CLOUDS

2015 ◽  
Vol II-3/W5 ◽  
pp. 89-96 ◽  
Author(s):  
M. Weinmann ◽  
B. Jutzi
Keyword(s):  
3D Reconstruction ◽  
Laser Scanning ◽  
Incidence Angle ◽  
Point Clouds ◽  
Urban Environments ◽  
Coordinate Frame ◽  
Consistency Check ◽  
Geometric Point ◽  
Feature Correspondences ◽  
Urban Accessibility

The faithful 3D reconstruction of urban environments is an important prerequisite for tasks such as city modeling, scene interpretation or urban accessibility analysis. Typically, a dense and accurate 3D reconstruction is acquired with terrestrial laser scanning (TLS) systems by capturing several scans from different locations, and the respective point clouds have to be aligned correctly in a common coordinate frame. In this paper, we present an accurate and robust method for a keypoint-based registration of unordered point clouds via projective scan matching. Thereby, we involve a consistency check which removes unreliable feature correspondences and thus increases the ratio of inlier correspondences which, in turn, leads to a faster convergence of the RANSAC algorithm towards a suitable solution. This consistency check is fully generic and it not only favors geometrically smooth object surfaces, but also those object surfaces with a reasonable incidence angle. We demonstrate the performance of the proposed methodology on a standard TLS benchmark dataset and show that a highly accurate and robust registration may be achieved in a fully automatic manner without using artificial markers.

scholarly journals COARSE POINT CLOUD REGISTRATION BY EGI MATCHING OF VOXEL CLUSTERS

2016 ◽  
Vol III-5 ◽  
pp. 97-103 ◽  
Author(s):  
Jinhu Wang ◽  
Roderik Lindenbergh ◽  
Yueqian Shen ◽  
Massimo Menenti
Keyword(s):  
Laser Scanning ◽  
Principal Component ◽  
Point Clouds ◽  
Data Sampling ◽  
Surface Geometry ◽  
Registration Method ◽  
Input Point ◽  
Coarse Registration ◽  
Point Distance ◽  
Fine Registration

Laser scanning samples the surface geometry of objects efficiently and records versatile information as point clouds. However, often more scans are required to fully cover a scene. Therefore, a registration step is required that transforms the different scans into a common coordinate system. The registration of point clouds is usually conducted in two steps, i.e. coarse registration followed by fine registration. In this study an automatic marker-free coarse registration method for pair-wise scans is presented. First the two input point clouds are re-sampled as voxels and dimensionality features of the voxels are determined by principal component analysis (PCA). Then voxel cells with the same dimensionality are clustered. Next, the Extended Gaussian Image (EGI) descriptor of those voxel clusters are constructed using significant eigenvectors of each voxel in the cluster. Correspondences between clusters in source and target data are obtained according to the similarity between their EGI descriptors. The random sampling consensus (RANSAC) algorithm is employed to remove outlying correspondences until a coarse alignment is obtained. If necessary, a fine registration is performed in a final step. This new method is illustrated on scan data sampling two indoor scenarios. The results of the tests are evaluated by computing the point to point distance between the two input point clouds. The presented two tests resulted in mean distances of 7.6 mm and 9.5 mm respectively, which are adequate for fine registration.

scholarly journals Terrestrial laser scanning in monitoring of anthropogenic objects

2017 ◽  
Vol 66 (2) ◽  
pp. 347-364
Author(s):  
Janina Zaczek-Peplinska ◽  
Maria Kowalska
Keyword(s):  
Laser Scanning ◽  
Incidence Angle ◽  
Geometric Analysis ◽  
Laser Scanner ◽  
Terrestrial Laser Scanning ◽  
Point Clouds ◽  
Angle Of Incidence ◽  
Point Distribution ◽  
Common Coordinate System ◽  
Cloud Of Points

Abstract The registered xyz coordinates in the form of a point cloud captured by terrestrial laser scanner and the intensity values (I) assigned to them make it possible to perform geometric and spectral analyses. Comparison of point clouds registered in different time periods requires conversion of the data to a common coordinate system and proper data selection is necessary. Factors like point distribution dependant on the distance between the scanner and the surveyed surface, angle of incidence, tasked scan’s density and intensity value have to be taken into consideration. A prerequisite for running a correct analysis of the obtained point clouds registered during periodic measurements using a laser scanner is the ability to determine the quality and accuracy of the analysed data. The article presents a concept of spectral data adjustment based on geometric analysis of a surface as well as examples of geometric analyses integrating geometric and physical data in one cloud of points: cloud point coordinates, recorded intensity values, and thermal images of an object. The experiments described here show multiple possibilities of usage of terrestrial laser scanning data and display the necessity of using multi-aspect and multi-source analyses in anthropogenic object monitoring. The article presents examples of multisource data analyses with regard to Intensity value correction due to the beam’s incidence angle. The measurements were performed using a Leica Nova MS50 scanning total station, Z+F Imager 5010 scanner and the integrated Z+F T-Cam thermal camera.

scholarly journals Rockfall monitoring by Terrestrial Laser Scanning – case study of the basaltic rock face at Castellfollit de la Roca (Catalonia, Spain)

2011 ◽  
Vol 11 (3) ◽  
pp. 829-841 ◽  
Author(s):  
A. Abellán ◽  
J. M. Vilaplana ◽  
J. Calvet ◽  
D. García-Sellés ◽  
E. Asensio
Keyword(s):  
Urban Areas ◽  
Laser Scanning ◽  
Mass Movement ◽  
Laser Scanner ◽  
Point Clouds ◽  
Basaltic Rock ◽  
Historical Record ◽  
Rock Face ◽  
The Village

Abstract. This case study deals with a rock face monitoring in urban areas using a Terrestrial Laser Scanner. The pilot study area is an almost vertical, fifty meter high cliff, on top of which the village of Castellfollit de la Roca is located. Rockfall activity is currently causing a retreat of the rock face, which may endanger the houses located at its edge. TLS datasets consist of high density 3-D point clouds acquired from five stations, nine times in a time span of 22 months (from March 2006 to January 2008). The change detection, i.e. rockfalls, was performed through a sequential comparison of datasets. Two types of mass movement were detected in the monitoring period: (a) detachment of single basaltic columns, with magnitudes below 1.5 m3 and (b) detachment of groups of columns, with magnitudes of 1.5 to 150 m3. Furthermore, the historical record revealed (c) the occurrence of slab failures with magnitudes higher than 150 m3. Displacements of a likely slab failure were measured, suggesting an apparent stationary stage. Even failures are clearly episodic, our results, together with the study of the historical record, enabled us to estimate a mean detachment of material from 46 to 91.5 m3 year−1. The application of TLS considerably improved our understanding of rockfall phenomena in the study area.

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