1,720,970 research outputs found
Distributed optical fiber sensors and terrestrial laser scanner surveys for the monitoring of an underground marble quarry
Full text linkThe sensing applications nowadays are always more used for structural and engineering-geological applications. In this work, an experimental monitoring system of an underground marble quarry, located in the Apuan Alps (Tuscany, Italy) is presented.
The system is composed by Distributed Optical Fiber Sensors (DOFS) based on Brillouin Frequency Shift (BFS). By using a control unit, multitemporal data of strain and temperature were measured thanks to the installation of 250 linear meters of DOFS placed around two pillars.
Terrestrial Laser Scanning (TLS) surveys, aided by GNSS (Global Navigation Satellite System) and TS (Total Station) measurements, were executed with the aim of: i) identifying physically inaccessible rock joints (i.e. height of the pillars), ii) georeferencing the DOFS and, iii) locating any strain phenomenon. The integration of a DOFS monitoring system with geomatic technologies has given the possibility to initialize a real-time monitoring system aimed at protecting the safety of the workers from possible rocky wall collapses.
The results obtained in this work are the texturized 3D model of the analyzed pillars, the DEM and the orthophoto of the quarry, and the profiles of BFS, strain and temperature variation. This research was funded by Tuscany Region (Italy) though the POR FESR 2014-2020 plan
Fracture mapping in challenging environment: a 3D virtual reality approach combining terrestrial LiDAR and high definition images
Full text linkArticleThis is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.The latest technological developments in computer vision allow the creation of georeferenced, non-immersive desktop virtual reality (VR) environments. VR uses a computer to produce a simulated three-dimensional world in which it is possible to interact with objects and derive metric and thematic data. In this context, modern geomatic tools enable the remote acquisition of information that can be used to produce georeferenced high-definition 3D models: these can be used to create a VR in support of rock mass data processing, analysis, and interpretation. Data from laser scanning and high quality images were combined to map deterministically and characterise discontinuities with the aim of creating accurate rock mass models. Discontinuities were compared with data from traditional engineering-geological surveys in order to check the level of accuracy in terms of the attitude of individual joints and sets. The quality of data collected through geomatic surveys and field measurements in two marble quarries of the Apuan Alps (Italy) was very satisfactory. Some fundamental geotechnical indices (e.g. joint roughness, alteration, opening, moisture, and infill) were also included in the VR models. Data were grouped, analysed, and shared in a single repository for VR visualization and stability analysis in order to study the interaction between geology and human activities.The authors gratefully acknowledge the assistance of the personal of the Romana Quarry and particularly Corniani M. This paper was possible because of support from the Tuscany Region Research Project known as “Health and safety in the quarries of ornamental stones—SECURECAVE”. The authors acknowledge Pellegri M and Gullì D (Local Sanitary Agency n.1, Mining Engineering Operative Unit—Department of Prevention) and Riccucci S (Centre of GeoTechnologies, University of Siena) for their support of this research
3D geological modelling in support of underground mining industry
No full textThe present paper describes a working approach that involves the combination of Terrestrial Laser Scanning (TLS) and traditional geological surveys for creating the three-dimensional model of an underground quarry located on the Apuan Alps (Italy). The final model includes information on the geological structure and marketable marble varieties. TLS can be used to obtain detailed and accurate geometrical information in short working times by generating several point clouds that can accurately model the detected surfaces. The study area comprises a network of tunnels, for a total length of about 140 meters, and 20 different scan positions were necessary to cover the entire area. In order to register all the point clouds data to a unique reference system, a topographic survey was conducted. The coordinates of some optical targets, positioned at specific locations within the excavation area, were measured by employing a Total Station and two GPS receivers. Differential GPS surveys and post-processing procedures have guaranteed a sub-centimetric accuracy of the targets and, consequently, of the point clouds. From the 3D use of the data, the new topographic map of the quarry was generated at a scale of 1:500, and several 2D cross sections were created for better understanding of the quarry's actual scenario. The structural and morphological limits of the quarry surfaces were restituted directly from the point cloud data. Further, “non uniform rational basis-spline” surfaces (NURBS) were created by employing a specific modelling software, which allowed to create the 3D model of the quarry. The application of NURBS surfaces, instead of meshes has turned out to be a better option in terms of speed, accuracy, control of operations and for the requirement of powerful compute.
Detailed traditional geological were carried out and a new geological map including the marketable marble varieties was created. Five detailed geological cross sections were drawn by combining both surface and sub-surface data. Finally, the 3D geological model of the area was generated. The combination of the two models has helped in understanding the relationship between quarry and marble deposit and it allowed to make exact measurements of distances and to quantify the extractable marble volumes.
The present working approach can be adapted in different geological contexts, since it allowed to obtain a huge amount of data in short working times without sacrificing details and accuracy. Such properties make of it an important instrument to improve cultivation plans for both safety and commercial reasons
Hazard Assessment of Rocky Slopes: An Integrated Photogrammetry–GIS Approach Including Fracture Density and Probability of Failure Data
Full text linkNatural rock slopes require accurate engineering–geological characterization to determine their stability conditions. Given that a natural rock mass is often characterized by a non-uniform fracture distribution, the correct, detailed, and accurate characterization of the discontinuity pattern of the
rock mass is essential. This is crucial, for example, for identifying the possibility and the probability of kinematic releases. In addition, complete stability analyses of possible rockfall events should be performed and used to create hazard maps capable of identifying the most dangerous parts of a rock
mass. This paper shows a working approach that combines traditional geological surveys and remote sensing techniques for engineering–geological investigations in a natural rock slope in Northern Italy. Discontinuities were identified and mapped in a deterministic way by using semi-automatic
procedures that were based on detailed 3D Unmanned Aerial Vehicle photogrammetric-based point cloud data and provided georeferenced representations of thousands of fractures. In this way, detailed documentation of the geo-mechanical and geo-structural characteristics of discontinuities were obtained and subsequently used to create fracture density maps. Then, traditional kinematic analyses and probabilistic stability analyses were performed using limit equilibrium methods. The results were then managed in a GIS environment to create a final hazard map that classifies different portions of the rock slope based on three factors: kinematic predisposition to rockfall (planar sliding, wedge sliding, toppling), fracture density, and probability of failure. The integration of the three hazard factors allowed the identification of the most hazardous areas through a deterministic and accurate procedure, with a high level of reliability. The adopted approach can therefore be very useful to determine the areas in which to prioritize remediation measures with the aim of reducing the level of risk
Excavation stability analysis in an underground marble quarry in the Apuan Alps (Italy): Application of terrestrial LIDAR, conventional methods and numerical modeling
No full textThe excavation of tunnels in a rock mass changes the existing stress state and initiates deformation processes that, in some cases, can cause instability. Stability investigations, using methodologies capable of verifying both the safety conditions and of representing new scenarios in underground works can be greatly enhanced through the use of high-resolution 3D images acquired in combination with ground-based LiDAR. Data from ground-based LiDAR allows the extraction of geological and structural characteristics of the rock mass such as geometries, attitudes, persistence and spacing of joints, even in inaccessible areas. High definition terrestrial laser scanning was adopted in an underground marble quarry, called "Romana", located in the Apuan Alps (Italy), as a support for the geological, geostructural and engineering geological study. Discontinuities were identified and mapped in a deterministic way by using the Leica TruView plug-in which manages laser scanning data and allows representation of the fractures in a georeferenced way either by arcs or by a sequence of aligned points. Given the large quantity of information collected, data were filtered and added to a geodatabase that, after GIS processing and additional in situ engineering geological surveys, was used to create thematic maps illustrating the fracture trends. In this way detailed documentation of the geomechanical and geostructural characteristics of the discontinuities was obtained and subsequently used to model the face stability in different zones of the tunnels.
Preliminary analyses were performed by means of numerical modeling in order to calculate approximate stress values around the excavation, and to understand how they change when perturbed. The simulations were carried out using both finite element, (Phase2; without discontinuities), and distinct element methods (UDEC; including discontinuities derived deterministically from remote sensing data). The calculated stress values were then used to perform a 3D stability analysis of excavation rock wedges using block theory software, Unwedge. Model results showed that the presence of discontinuities considerably affects both the stress orientation and stress magnitude around the excavation zone, and must be taken into account to ensure accurate stability analyses. In this context the use of the most recent technologies of remote sensing, together with traditional engineering geological surveys, can provide an important and fundamental contribution. Results of the study to date have been analyzed and discussed with the managers of the underground quarry in order to optimize the planning of future excavations
Analisi di stabilità di un pendio detritico montano tramite impiego di georadar installato su drone
Full text linkIl presente lavoro descrive le attività svolte in merito alla verifica della stabilità di un pendio detritico naturale posto in zona montana di difficile accesso nella catena delle Alpi Occidentali.
I dati necessari alle analisi sono stati raccolti ed elaborati attraverso tecniche geomatiche quali, in particolare, rilievi fotogrammetrici con drone con lo scopo di acquisire delle foto prospettiche dalle quali produrre una nuvola di punti georeferenziata e successivamente un ortofotomosaico. Il rilievo è stato eseguito con un drone tipo DJI Mavic 2 Pro. Contestualmente ai rilievi fotogrammetrici sono stati eseguiti rilievi topografici di Ground Control Points necessari nella fase di orientamento esterno dei fotogrammi. I fotogrammi sono stati elaborati utilizzando il software Agisoft Metashape. La nuvola 3D densa prodotta è stata successivamente interpolata in modo da generare un modello digitale denso della superficie (DDSM) in formato raster. Sulla base del DDSM sono state ortocorrette le immagini fotografiche ottenendo degli ortofotomosaici.
Allo scopo di determinare lo spessore della coltre detritica naturale al di sopra del bedrock, sono stati eseguiti 2 rilievi geofisici utilizzando lo strumento COBRA Plug‐In GPR Model SE-150, installato su drone DJI M600Pro. L’indagine si è svolta sorvolandolo direttamente l’area di interesse a circa 1.5 metri dalla superficie e raggiungendo aree altrimenti non investigabili per motivi di sicurezza. I dati del rilievo georadar sono stati elaborati con l’ausilio dell’applicativo PRISM® 2.6.
La nuvola di punti 3D ottenuta dal rilievo fotogrammetrico ha permesso la ricostruzione delle corrette geometrie del corpo detritico naturale. Tramite il software open source CloudCompare Omnia, sono stati selezionati profili rappresentativi dell’area di interesse in seguito importati all’interno del software RocScience Slide2. La ricostruzione della profondità del contatto tra la copertura detritica e il bedrock è stata eseguita estrapolando le informazioni ricavate dalle tracce georadar più prossime al profilo di interesse.
Le verifiche sono state effettuate valutando diversi scenari quali: condizioni statiche, dinamiche con presenza di sisma, condizioni statiche con presenza di neve e dinamiche con presenza contemporanea di neve e sisma.
L’impiego del georadar installato su un drone si è dimostrato un ottimo metodo di indagine in situazioni in cui l’area di studio risulta essere inaccessibile alle classiche analisi geofisiche per motivi morfologici e di sicurezza. La combinazione quindi di dati ottenuti tramite rilievi topo-cartografici e areofotogrammetrici con rilievo geofisico da drone ha permesso lo studio della stabilità di un versante naturale in area critica
Ground Displacements Estimation through GNSS and Geometric Leveling: A Geological Interpretation of the 2016–2017 Seismic Sequence in Central Italy
Full text linkBetween August 2016 and January 2017, a very energetic seismic sequence induced substantial horizontal and vertical ground displacements in the Central Italian Apennines. After this event, the Italian Military Geographical Institute (IGM), owner and manager of the Italian geodetic networks, executed several topographic surveys in the earthquake area in order to update the coordinates of vertices belonging to the IGM95 geodetic network. The measurements began in the areas where the most significant deformation occurred: the localities of Amatrice and Accumoli, in the Rieti Prov-ince, and the area covering Norcia and Castelluccio, in the Province of Perugia, all the way to Visso (Province of Macerata). The activities described in this paper focused on the updated measurement of the IGM95 network points through GNSS and the restatement of extensive parts of the high precision geometric lines that were levelled until reaching stable zones. This unprecedented amount of data was used for a new geological interpretation of the seismic sequence, which confirms some of the previous hypotheses of the scientific community. In the analyzed territory, the latest estimate of the geodetic position points has allowed for an accurate determination of the east and the north and of the altitude components of the displacement induced by the earthquake through a comparison with the previous coordinates. The results confirm that the seismicity was induced by normal faults system activity. Still, they also indicate the possible influence of a significant regional thrust that conditioned the propagation of the seismicity in the area. The obtained maps of the displacement are coherent with other geodetic works and with a rupture propagation driven by the documented geotectonic structure
Il Lidar terrestre per la caratterizzazione degli ammassi rocciosi
No full textOperare in sicurezza e in tempi brevi è un aspetto importante quando si vuole eseguire uno studio geologico, soprattutto in cave in sotterraneo. L’attività estrattiva implica l'impossibilità di accedere ad alcune aree, perché non sicure, oppure non permette di soffermarsi su un affioramento per effettuare le osservazioni geologiche del caso.
Per questo motivo negli ultimi anni si è sviluppato un nuovo approccio di rilevamento attraverso il quale si possono ottenere modelli tridimensionali ad altissima risoluzione delle superfici investigate. In quest'ottica il lidar terrestre rappresenta attualmente uno dei più accurati e veloci strumenti investigativi per l’acquisizione a distanza d’informazioni geometriche riguardanti le superfici osservate. Grazie a tali peculiarità è possibile proporre questa tecnologia per la caratterizzazione degli ammassi rocciosi e, in particolare, per la mappatura di dettaglio delle discontinuità che lo caratterizzano.
Tuttavia, il solo dato puntuale ricavabile dallo scanner, senza foto di dettaglio, spesso non consente un’osservazione completa delle discontinuità tantomeno una corretta interpretazione. Da questa limitazione nasce l’idea di riconoscere e misurare le fratture non sulla nuvola di punti o sul Modello Digitale della Superficie, come viene spesso fatto nelle cave a cielo aperto o in versanti naturali, ma sfruttando il dato fotografico tramite il plug-in, libero per MicrosoftTM Internet Explorer, denominato LeicaTM Truview. Quest’ultimo permette di visualizzare la nuvola di punti attraverso una serie di immagini panoramiche (3D) ad alta risoluzione, di modificare la vista rispetto al punto di osservazione e di rappresentare le fratture in forma di insiemi di punti allineati e georeferenziati.
L’analisi spaziale dei dati puntuali permette successivamente di ricostruire la giacitura di ogni singola frattura identificata a monitor e misurare la sua persistenza e spaziatura. L'accuratezza con la quale il dataset geomatico viene ricostruito si verifica confrontando, nelle aree accessibili, gli stereonet ottenuti da un’analisi di densità con quelli elaborati a partire da misure effettuate in modo tradizionale (con bussola da geologo).
L’integrazione tra i rilievi geomatici e geomeccanici permette infine di creare un nuovo dataset costituito da immagini 3D ad alta risoluzione sulle quali vengono implementate le informazioni strutturali e geomeccaniche rilevate in campagna.
Infatti, nonostante i vantaggi ricavabili dalla procedura illustrata, non è possibile prescindere dal rilievo tradizionale di campagna per la misura di altre proprietà fondamentali delle singole discontinuità quali la scabrezza, l’alterazione, la resistenza a compressione, l’apertura, l’umidità, il riempimento e la terminazione.
In definitiva, i passi in avanti effettuati in campo geologico verso il digitale sono enormi anche se l'integrazione con i classici metodi di rilevamento è ancora oggi un fattore imprescindibile
An integrated remote sensing-GIS approach for the analysis of an open pit in the Carrara marble district, Italy: Slope stability assessment through kinematic and numerical methods
No full textOver the last decade, terrestrial laser scanning and digital terrestrial photogrammetry techniques have been increasingly used in the geometrical characterization of rock slopes. These techniques provide innovative remote sensing tools which overcome the frequent problem of rock slope inaccessibility. Comprehensive datasets characterizing the structural geological setting and geometry of the slopes can be obtained. The derived information is very useful in rock slope investigations and finds application in a wide variety of geotechnical and mine operations. In this research an integrated remote sensing – GIS approach is proposed for the deterministic kinematic characterization of the Lorano open pit in the Apuan Alps of Italy. Based on the results of geomatic and engineering geological surveys, additional geomechanical analysis using a 3D finite difference method will be presented in order to provide a better understanding of the role of stress-induced damage on slope performance
Application of an integrated geotechnical and topographic monitoring system in the Lorano marble quarry (Apuan Alps, Italy)
No full textPublishedThis is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.geomorph.2015.04.009Accurate slope stability analysis is essential for human activity in high-risk geological contexts. This may, however, not be enough in the case of quarrying where the dynamic and evolving environment also requires effective monitoring. A well-designed monitoring system requires the acquisition of a huge dataset over time, improving knowledge of the study area and helping to refine prediction from stability analysis.This paper reports the implementation of an integrated monitoring system in a marble quarry in the Apuan Alps (Italy) and some of the results obtained. The equipment consists of a traditional geotechnical monitoring system (extensometers, crackmeters and clinometers) and two modern topographic monitoring systems (a terrestrial interferometer and a robotic total station). This work aims to provide in-depth knowledge of the large scale rock mass behaviour as a result of marble exploitation, thereby allowing continuous excavation. The results highlight the importance of integrating different monitoring systems.The present study was undertaken within the framework of the Italian National Research Project PRIN2009, funded by the Ministry of Education, Universities and Research, which involves the collaboration between the University of Siena, “La Sapienza” University of Rome, and USL1 of Massa and Carrara (Mining Engineering Operative Unit - Department of Prevention)
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