1,721,051 research outputs found
Assessment of the behavior of an active earth-slide by means of calibration between numerical analysis and field monitoring
No full textThe assessment of hazards associated with active landslides and the related risk management takes advantage nowadays of using the integration of information arising from field monitoring data, including both displacement data, at ground surface and at depth, and pore pressure measurements well distributed throughout the landslide area, along with the results of numerical models. This paper provides an example of the application of this methodological approach to a case study represented by an active sector of the large Montaguto earthslide, located in the Italian Southern Apennines, which has shown in recent years a continuous slow movement, despite the draining interventions executed in 2011 and the general stability of the other portions of the earthslide. The near real-time topographic monitoring network installed in 2010 shows the presence of different kinematic sectors within the same landslide body, characterised by different velocities and evolution trends. After the proper emergency phase occurred in 2010, a specific area has still shown in 2011 and 2012 clear signs of activity, with acceleration stages generally recorded in the Spring. In order to explore the factors that presumably control the activity of this landslide sector, a two-dimensional finite element model has been developed by using PLAXIS-2D code. Based on the available geological information, pore water pressure measurements and soil geotechnical properties, the numerical results indicate the role of geometry of the landslide mass in sector E as a factor promoting the instability of this specific area. The numerical results are in good agreement with the displacement field measured throughout the landslide channel and confirm that numerical modelling can represent a reliable support for the interpretation of the landslide failure mechanism and the corresponding evolution, when calibrated against the in situ landslide behaviour reconstructed through a monitoring system
Reliability and uncertainties of the analysis of an unstable rock slope performed on RPAS digital outcrop models: The case of the gallivaggio landslide (Western Alps, Italy)
Full text linkA stability investigation based on Digital Outcrop Models (DOMs) acquired in emergency conditions by photogrammetric surveys based on Remote Piloted Aerial System (RPAS) was conducted on an unstable rock slope near Gallivaggio (Western Alps, Italy). The predicted mechanism of failure and volume of the unstable portion of the slope were successively verified on the DOMs acquired after the rockfall that effectively collapsed the May 29th, 2018. The comparison of the pre-and post-landslide 3D models shows that the estimated mode of failure was substantially correct. At the same time, the predicted volume of rock involved in the landslide was overestimated by around 10%. To verify if this error was due to the limited accuracy of the models georeferenced in emergency considering only the Global Navigation Satellite System/Inertial Measurement Unit (GNSS/IMU)-information of RPAS, several Ground Control Points (GCPs) were acquired after the failure. The analyses indicate that the instrumental error in the volume calculation due to the direct-georeferencing method is only of the 1.7%. In contrast, the significant part is due to the geological uncertainty in the reconstruction of the real irregular geometry of the invisible part of the failure surface. The results, however, confirm the satisfying relative accuracy of the direct-georeferenced DOMs, compatible with most geological and geoengineering purposes
The Montaguto earthflow: A back-analysis of the process of landslide propagation
No full textEarthflow and mudflow processes represent a class of landslides that, owing to their typical long run-out, may generally induce huge damages to infrastructure lines, with negative economic impacts. Therefore, the analysis of the landslide propagation with time in such cases can provide useful information to mitigate landslide risk. The present paper discusses the case history of a huge earthflow developed in 2005-2006 in the area of Montaguto town (Southern Apennines, Italy), that produced significant damages to a national road and a national railway at the slope toe. The average displacement rate during the first critical stage of propagation was of some m/day. The aim of this contribution is the reconstruction of the propagation stage of this landslide during the first high-mobility stage. A detailed geomorphological analysis aimed at defining the main features of the in-situ landslide propagation is firstly described. Later on, a back-analysis of the kinematical features of the same landslide process, based on a simple infinite-slope sliding-consolidation model, is presented to investigate the role of different factors in the process of landslide propagation. The application of this analytical solution suggests that the development of high excess pore water pressures due to undrained loading processes and the consequent consolidation process can represent a reasonable way to explain the earthflow mobility. The application of the analytical model to the specific case study is also supported by the field evidence of the existence of excess pore water pressures in the landslide mass which have been measured in situ during the recent monitoring campaign and the corresponding data are also discussed in the work. © 2013 Elsevier B.V
An Open-Source Algorithm for 3D ROck Slope Kinematic Analysis (ROKA)
No full textThe Markland test is one of the most diffused and adopted methods of kinematic analysis for the identification of critical intersections of rock discontinuities that could generate rock failures. Traditionally, the kinematic analysis is based on the use of a stereographic approach that is able to identify the critical combination between the orientations of discontinuities and the rock wall. The recent improvements in the use of Digital Outcrop Models (DOMs) created the conditions for the development of a new automatized approach. We present ROck Slope Kinematic Analysis (ROKA) which is an open-source algorithm aimed at performing the Kinematic Analysis using the discontinuity measures collected onto a 3D DOM. The presented algorithm is able to make a local identification of the possible critical combination between the identified discontinuities and the orientation of the slope. Using this approach, the algorithm is able to identify on the slope the presence of critical combinations according to the traditional kinematic analysis of planar failure, flexural toppling, wedge failure, and direct toppling modes of failures and then visualize them on DOMs. In this way, the traditional approach is more effective and can be adopted for a more detailed analysis of large and complex areas
DICE: An open-source MATLAB application for quantification and parametrization of digital outcrop model-based fracture datasets
No full textAn open-source MATLAB application (app) named Discontinuity Intensity Calculator and Estimator (DICE) was developed in order to quantitatively characterize the fractures, or in more general, discontinuities within a rocky outcrop in three-dimensional (3D) digital data, such as digital outcrop model (DOM). The workflow proposed for the parametrization of the discontinuities consists of the following steps: (1) Analysis and mapping of the fractures detected within the 3D DOMs; (2) Calculation of the orientation, position and dimensions of discontinuities that are represented by best-fit circular planes; (3) Determining the discontinuity parameters (dimension, distribution, spacing and intensity) by the DICE algorithm using different 3D oriented sampling techniques (3D oriented scanline, 3D oriented circular scan window and spherical scan volume). Different sampling methods were bench tested with a synthetic, as well as a natural case study, and compared in order to understand the advantages and limitations of each technique. The 3D oriented circular scan window appears to be the most effective method for fracture intensity estimation with high accuracy (error 0.4%) and stability with variations in scan radius. (c) 2023 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/)
The use of remotely piloted aircraft systems (RPASs) for natural hazards monitoring and management
No full textThe number of scientific studies that consider possible applications of remotely piloted aircraft systems (RPASs) for the management of natural hazards effects and the identification of occurred damages strongly increased in the last decade. Nowadays, in the scientific community, the use of these systems is not a novelty, but a deeper analysis of the literature shows a lack of codified complex methodologies that can be used not only for scientific experiments but also for normal codified emergency operations. RPASs can acquire on-demand ultra-high-resolution images that can be used for the identification of active processes such as landslides or volcanic activities but can also define the effects of earthquakes, wildfires and floods. In this paper, we present a review of published literature that describes experimental methodologies developed for the study and monitoring of natural hazards
Monthly velocity and seasonal variations of the Mont Blanc glaciers derived from Sentinel-2 between 2016 and 2024
No full textWe investigated the temporal variability of the surface velocity of 30 glaciers in the Mont Blanc massif (European Alps). We calculated the monthly velocity between 2016 and 2024 using digital image correlation of Sentinel-2 optical imagery. The main objectives of the study were (i) to characterize the variability of the velocity fields of such glaciers (referring to both their temporal seasonal and inter-annual and spatial variations) and (ii) to investigate relationships between the morphology of glaciers and their kinematics. We measured monthly velocities varying from 12.7 to 487.4 m yr(-1). We observed an overall decrease in the velocity between 2016 and 2019 and an unexpected rise in 2020-2022, which are especially visible in most glaciers on the southern side of the massif. Considering the whole period, half of the glaciers showed positive acceleration, which reached values > 4 m yr(-2) in three glaciers. In general, the trend's absolute value in the cold season is higher in the case of positive acceleration and lower in the case of negative acceleration. We found that smaller glaciers have a more pronounced seasonality, with winter-summer velocity differences of 50 %-100 %. Finally, in 2016, 2018, and 2022, we observed an exceptionally high winter-summer velocity difference in the 0.3 km2 wide Charpoua Glacier, when summer velocities increased by 1 order of magnitude
Impact of Deep-seated Gravitational Slope Deformation on urban areas and large infrastructures in the Italian Western Alps
No full textDeep-seated Gravitational Slope Deformations (DsGSDs) are huge ground-deformation slow evolving phenomena, highly widespread in alpine territory. Their long-lasting evolution, with continuous deformation rate, may represents a natural hazard, able to endanger various anthropic structures and infrastructures. Until today, the development of technical and regulatory tools, aimed to effectively manage the interactions between DsGSDs and anthropic elements, has been generally lightly considered in risk management and land use planning. The definition of the type and severity of impacts on the anthropic elements, becomes increasingly important in terms of urban planning and risk management, and deserve an update in the current adopted procedures. Focusing on the Western Italian Alps, we implemented an interdisciplinary analysis, based on multi-source data, by means of geoinformatics, remote sensing and archive consultation approaches. Intersecting DsGSDs available information with the urbanized territory in a Geographic Information System environment, we obtained, despite the high data heterogeneity, an overall framework of the existing interactions. Specifically, we defined the interactions between these large phenomena and buildings, roads and rail networks, and linear infrastructures, as penstocks, waterworks or dams, also highlighing the state of activity of the inventoried phenomena. Moreover, we analysed the degree of the DsGSD impacts on the anthropic elements, detecting and classifying all the documented damages within the Italian Western Alps territory. The obtained results highlight the need for an innovative approach in DsGSDs risk assessment, both in terms of the definition of their behavior over time and of their impacts on the anthropic elements, for a more effective land use planning and a proper handling of these phenomena in the legislation framework
Detection and geometric characterization of rock mass discontinuities using a 3D high-resolution digital outcrop model generated from RPAS imagery – Ormea rock slope, Italy
Full text linkThe use of a remotely piloted aircraft system (RPAS) and digital photogrammetry is valuable for the detection of discontinuities in areas where field mapping and terrestrial photogrammetry or laser scanner surveys cannot be employed because the slope is unsafe, inaccessible, or characterized by a complex geometry with areas not visible from the ground. Using the Structure-from-Motion method, the acquired images can be used to create a 3D texturized digital outcrop model (TDOM) and a detailed point cloud representing the rock outcrop. Discontinuity orientations in a complex rock outcrop in Italy were mapped in the field using a geological compass and by manual and automated techniques using a TDOM and point cloud generated from RPAS imagery. There was a good agreement between the field measurements and manual mapping in the TDOM. Semi-automated discontinuity mapping using the point cloud was performed using the DSE, qFacet FM, and qFacet KD-tree methods applied to the same 3D model. Significant discrepancies were found between the semi-automatic and manual methods. In particular, the automatic methods did not adequately detect discontinuities that are perpendicular to the slope face (bedding planes in the case study). These differences in detection of discontinuities can adversely influence the kinematic analysis of potential rock slope failure mechanisms. We use the case study to demonstrate a workflow that can accurately map discontinuities with results comparable to field measurements. The combined use of TDOM and RPAS dramatically increases the discontinuity data because RPAS can supply a good coverage of inaccessible or hidden portions of the slope and TDOM is a powerful representation of the reality that can be used to map discontinuity orientations including those that are oriented perpendicular to the slope
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