71 research outputs found

    APPLICATION OF LASER SCANNING SURVEYING TO ROCK SLOPES RISK ASSESSMENT ANALYSIS

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    The methods for understanding rock instability mechanisms and for evaluating potential destructive scenarios are of great importance in risk assessment analysis dedicated to the establishment of appropriate prevention and mitigation actions. When the portion of the unstable rock mass is very large, effective actions to counteract the risks are complex and expensive. In these conditions, an optimal risk management cannot ignore procedures able to faster and accurately acquire i) geometrical data for modeling the geometry of the rock walls and implementing reliable forecasting models and ii) monitoring data able to describe the magnitude and the direction of deformation processes. These data contributes to the prediction of the behavior of a landslide if the measurements are acquired frequently and reliable numerical models can be implemented. Innovative geomatic techniques, based on GPS, Terrestrial Laser Scanning Surveying (TLS), automated total station and satellite and ground SAR Interferometry, have been recently applied to define the geometry and monitoring the displacements of unstable slopes. Among these, TLS is mainly adopted to generate detailed 3D models useful to reconstruct rock wall geometry by contributing to the estimation of geo-mechanical parameters, that is orientation, persistence and apparent spacing of rock discontinuities. Two examples of applications of TLS technique to the analysis of a large front in a quarry and of a rock shoulder of a dam are presented

    Analysis of rock masses belonging to the Apennine-Maghrebide Orogen by means of in situ and remote methodologies applied to rockfall risk assessment

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    The rockfall attitude of rock slopes threatening a strategic spot of eastern Sicily has been studied herein with the aims of testing an innovative methodology for the remote survey of fractured rock outcrops and of assessing the rockfall risk along an important transportation corridor through a quantitative probabilistic approach. The study area, often involved in rockfall events, which cause serious damage to private and public infrastructures, is one of the most relevant places of Sicily due to the great tourism rate recorded every year between the resorts of Taormina and Castelmola, which are also considered an outstanding example of cultural heritage. The innovative procedure of rock mass survey through InfraRed Thermography is tested and proposed herein for the study of the fracturing condition of intensely jointed rock masses, to find out what kind of information can be assessed in this field of rock mechanics. Although this technique is widely used in several scientific fields, its direct application for such purposes is still pioneering. In this thesis, thermal imaging campaigns, carried out under different climatic conditions, are described, and interesting considerations are proposed with reference to a Cooling Rate Index, estimated to study how rock masses, conditioned by their fracture nets, behave during the heat transfer towards the external environment. Such an index was related to the degree of fracturing of the rock masses to find a relationship linking thermal data to one of the main quantitative fracturing indexes. Results return interesting matches between some geostructural features and thermal outputs, demonstrating the reliability of the application of such methodology to bare rock masses. Moreover, new experimental considerations are proposed, laying the foundations for future studies aimed to further validate the InfraRed Thermography as an effective remote survey technique. Risk assessment was carried out through the quantitative approach of the Event Tree Analysis, which was properly customized to take into account the peculiarity of the area and of the road path. Rock mass surveys, trajectory simulations and probabilistic models were taken into account with the aim of calculating the probability related to possible scenarios in case of rockfalls. Achieved outcomes demonstrate that such procedure is a reliable tool, which can be taken as reference to calibrate further risk models in comparable contexts of the world, where rockfall threaten communication routes. This would represent a helpful instrument to the scientific community and to local authorities dealing with one of the most troublesome natural phenomena affecting the public safety

    Modelling the Influence of Geological Structures in Paleo Rock Avalanche Failures Using Field and Remote Sensing Data

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    This paper focuses on the back analysis of an ancient, catastrophic rock avalanche located in the small city of Lettopalena (Chieti, Italy). The integrated use of various investigation methods was employed for landslide analysis, including the use of traditional manual surveys and remote sensing (RS) mapping for the identification of geological structures. The outputs of the manual and RS surveys were then utilised to numerically model the landslide using a 2D distinct element method. A series of numerical simulations were undertaken to perform a sensitivity analysis to investigate the uncertainty of discontinuity properties on the slope stability analysis and provide further insight into the landslide failure mechanism. Both numerical modelling and field investigations indicate that the landslide was controlled by translational sliding along a folded bedding plane, with toe removal because of river erosion. This generated daylighting of the bedding plane, creating kinematic freedom for the landslide. The formation of lateral and rear release surfaces was influenced by the orientation of the discrete fracture network. Due to the presence of an anticline, the landslide region was constrained in the middle-lower section of the slope, where the higher inclination of the bedding plane was detected. The landslide is characterized by a step-path slip surface at the toe of the slope, which was observed both in the modelling and the field. This paper highlights the combined use of a geological model and numerical modelling to provide an improved understanding of the origin and development of rock avalanches under the influence of river erosion, anticline structures, and related faults and fractures

    Training of Crisis Mappers and Map Production from Multi-sensor Data: Vernazza Case Study (Cinque Terre National Park, Italy)

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    This aim of paper is to presents the development of a multidisciplinary project carried out by the cooperation between Politecnico di Torino and ITHACA (Information Technology for Humanitarian Assistance, Cooperation and Action). The goal of the project was the training in geospatial data acquiring and processing for students attending Architecture and Engineering Courses, in order to start up a team of "volunteer mappers". Indeed, the project is aimed to document the environmental and built heritage subject to disaster; the purpose is to improve the capabilities of the actors involved in the activities connected in geospatial data collection, integration and sharing. The proposed area for testing the training activities is the Cinque Terre National Park, registered in the World Heritage List since 1997. The area was affected by flood on the 25th of October 2011. According to other international experiences, the group is expected to be active after emergencies in order to upgrade maps, using data acquired by typical geomatic methods and techniques such as terrestrial and aerial Lidar, close-range and aerial photogrammetry, topographic and GNSS instruments etc.; or by non conventional systems and instruments such us UAV, mobile mapping etc. The ultimate goal is to implement a WebGIS platform to share all the data collected with local authorities and the Civil Protectio

    An Integrated Procedure to Assess the Stability of Coastal Rocky Cliffs: From UAV Close-Range Photogrammetry to Geomechanical Finite Element Modeling

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    The present paper explores the combination of unmanned aerial vehicle (UAV) photogrammetry and three-dimensional geomechanical modeling in the investigation of instability processes of long sectors of coastal rocky cliffs. The need of a reliable and detailed reconstruction of the geometry of the cliff surfaces, beside the geomechanical characterization of the rock materials, could represent a very challenging requirement for sub-vertical coastal cliffs overlooking the sea. Very often, no information could be acquired by alternative surveying methodologies, due to the absence of vantage points, and the fieldwork could pose a risk for personnel. The case study is represented by a 600 m long sea cliff located at Sant\u2019Andrea (Melendugno, Apulia, Italy). The cliff is characterized by a very complex geometrical setting, with a suggestive alternation of 10 to 20 m high vertical walls, with frequent caves, arches and rock-stacks. Initially, the rocky cliff surface was reconstructed at very fine spatial resolution from the combination of nadir and oblique images acquired by unmanned aerial vehicles. Successively, a limited area has been selected for further investigation. In particular, data refinement/decimation procedure has been assessed to find a convenient three-dimensional model to be used in the finite element geomechanical modeling without loss of information on the surface complexity. Finally, to test integrated procedure, the potential modes of failure of such sector of the investigated cliff were achieved. Results indicate that the most likely failure mechanism along the sea cliff examined is represented by the possible propagation of shear fractures or tensile failures along concave cliff portions or over-hanging due to previous collapses or erosion of the underlying rock volumes. The proposed approach to the investigation of coastal cliff stability has proven to be a possible and flexible tool in the rapid and highly-automated investigation of hazards to slope failure in coastal areas

    Comparing manual and remote sensing field discontinuity collection used in kinematic stability assessment of failed rock slopes

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    Este artículo propone una metodología de reconstrucción de superficies mediante SfM-MVS a partir de fotogragrafías y puntos de control replanteados con pequeños puntos de plastilina, posicionados en el talud mediante brújula.This work was supported by the University of Alicante, within the framework of project GRE14-04. Additional funding was obtained from the Spanish Government, project number TIN2014-55413-C2-2-P

    Temporal-spatial frequency rockfall data from open-pit highwalls using a low-cost monitoring system

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    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

    Numerical limitations of the attainment of the orientation of geological planes

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    The paper discusses limitations of analytical attainment of the attitude of a geological plane by using three non-collinear points. We present problems that arise during computing the orientation of a plane generated by almost collinear points. We referred these errors to floating-point arithmetic inaccuracies. To demonstrate the problem, we examined a surface of constant orientation. We used Delaunay triangulation to calculate its local orientation parameters. We introduced a new measure of collinearity applicable for collecting attitude of planar triangles. Using this measure we showed that certain planes generated by the triangulation cannot be treated as a reliable source of measurement. To examine the relationship between collinearity and orientation, we used a combinatorial algorithm to obtain all possible planes from the given set of points. A statistical criterion of rejecting almost collinear planes was suggested

    Training of Crisis Mappers and Map Production from Multi-sensor Data: Vernazza Case Study (Cinque Terre National Park, Italy)

    Get PDF
    This aim of paper is to presents the development of a multidisciplinary project carried out by the cooperation between Politecnico di Torino and ITHACA (Information Technology for Humanitarian Assistance, Cooperation and Action). The goal of the project was the training in geospatial data acquiring and processing for students attending Architecture and Engineering Courses, in order to start up a team of “volunteer mappers”. Indeed, the project is aimed to document the environmental and built heritage subject to disaster; the purpose is to improve the capabilities of the actors involved in the activities connected in geospatial data collection, integration and sharing. The proposed area for testing the training activities is the Cinque Terre National Park, registered in the World Heritage List since 1997. The area was affected by flood on the 25th of October 2011. According to other international experiences, the group is expected to be active after emergencies in order to upgrade maps, using data acquired by typical geomatic methods and techniques such as terrestrial and aerial Lidar, close-range and aerial photogrammetry, topographic and GNSS instruments etc.; or by non conventional systems and instruments such us UAV, mobile mapping etc. The ultimate goal is to implement a WebGIS platform to share all the data collected with local authorities and the Civil Protection

    A review of laser scanning for geological and geotechnical applications in underground mining

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    Laser scanning can provide timely assessments of mine sites despite adverse challenges in the operational environment. Although there are several published articles on laser scanning, there is a need to review them in the context of underground mining applications. To this end, a holistic review of laser scanning is presented including progress in 3D scanning systems, data capture/processing techniques and primary applications in underground mines. Laser scanning technology has advanced significantly in terms of mobility and mapping, but there are constraints in coherent and consistent data collection at certain mines due to feature deficiency, dynamics, and environmental influences such as dust and water. Studies suggest that laser scanning has matured over the years for change detection, clearance measurements and structure mapping applications. However, there is scope for improvements in lithology identification, surface parameter measurements, logistic tracking and autonomous navigation. Laser scanning has the potential to provide real-time solutions but the lack of infrastructure in underground mines for data transfer, geodetic networking and processing capacity remain limiting factors. Nevertheless, laser scanners are becoming an integral part of mine automation thanks to their affordability, accuracy and mobility, which should support their widespread usage in years to come
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