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Dangers naturels dans une commune de montagne, Ormont-Dessus (Excursion SVSN - Dimanche 3 octobre 2010)
No full textLes dangers naturels en Suisse: pratiques et développements: Comptes rendus de la deuxième Journée de Rencontre sur les Dangers Naturels (Université de Lausanne, 18 février 2011)
No full textSafeLand D41 : Review of Techniques for Landslide Detection, Fast Characterization, Rapid Mapping and Long-Term Monitoring
No full text
Radar Wave Principles, Interferometric Radar Distance-Meter and Differential SAR interferometry
No full textQdc-2d: A semi-automatic tool for 2d analysis of discontinuities for rock mass characterization
No full textQuantitative characterization of discontinuities is fundamental to define the mechanical behavior of discontinuous rock masses. Several techniques for the semi-automatic and automatic extraction of discontinuities and their properties from raw or processed point clouds have been introduced in the literature to overcome the limits of conventional field surveys and improve data accuracy. However, most of these techniques do not allow characterizing flat or subvertical outcrops because planar surfaces are difficult to detect within point clouds in these circumstances, with the drawback of undersampling the data and providing inappropriate results. In this case, 2D analysis on the fracture traces are more appropriate. Nevertheless, to our knowledge, few methods to perform quantitative analyses on discontinuities from orthorectified photos are publicly available and do not provide a complete characterization. We implemented scanline and window sampling methods in a digital environment to characterize rock masses affected by discontinuities perpendicular to the bedding from trace maps, thus exploiting the potentiality of remote sensing techniques for subvertical and low-relief outcrops. The routine, named QDC-2D (Quantitative Discontinuity Characterization, 2D) was compiled in MATLAB by testing a synthetic dataset and a real case study, from which a high-resolution orthophoto was obtained by means of Structure from Motion technique. Starting from a trace map, the routine semi-automatically classifies the discontinuity sets and calculates their mean spacing, frequency, trace length, and persistence. The fracture network is characterized by means of trace length, intensity, and density estimators. The block volume and shape are also estimated by adding information on the third dimension. The results of the 2D analysis agree with the input used to produce the synthetic dataset and with the data collected in the field by means of conventional geostructural and geomechanical techniques, ensuring the procedure’s reliability. The outcomes of the analysis were implemented in a Discrete Fracture Network model to evaluate their applicability for geomechanical modeling
Evaluation of InfraRed Thermography Supported by UAV and Field Surveys for Rock Mass Characterization in Complex Settings
Get PDFThe InfraRed Thermography (IRT) technique is gaining increasing popularity in the geo-sciences. Although several studies on the use of this technique for rock mass characterization were reported in the literature, its applicability is challenging in complex environments, characterized by poor accessibility, lithological heterogeneity, karst features and disturbances, such as vegetation and human activities. This paper reports the results of specific tests carried out to explore the application of IRT methods, supported by UAV surveys, for rock mass characterization in complex conditions. In detail, a 24-h monitoring was performed on an appropriate case study to assess which type of information can be collected and what issues can be expected. The results of the thermograms were compared with data reported in the literature and discussed. A novel method to detect correlations between the temperature profiles at the air-rock interfaces and the rock mass properties is presented. The main advantages, limitations and suggestions in order to take full advantage of the IRT technique in complex conditions are reported in the final section
Comparison of remote sensing techniques for geostructural analysis and cliff monitoring in coastal areas of high tourist attraction: the case study of Polignano a Mare (Southern Italy)
Get PDFRock slope failures in urban areas may represent a serious hazard for human life, as well as
private and public property, even on the occasion of sporadic episodes. Prevention and mitigation
measures indispensably require a proper rock mass characterization, which is often achieved by
means of time-consuming, costly and dangerous field surveys. In the last decades, remote sensing
devices such as high-resolution digital cameras, laser scanners and drones have been widely used as
supplementary techniques for rock slope analysis and monitoring, especially in poorly accessible
areas, or in sites of large extension. Although several methods for rock mass characterization by
means of remote sensing techniques have been reported in specific studies, there are very few
contributions that focused on comparing the different methods in an attempt to establish their
advantages and limitations. With this study, we performed digital photogrammetry, Terrestrial Laser
Scanning and Unmanned Aerial Vehicle surveys on a cliff located in a popular tourist attraction
site, characterized by complex geological and geomorphological settings, as well as by disturbance
elements such as vegetation and human activities. For each point cloud, we applied geostructural
analysis by means of semi-automatic methods, and then compared multi-temporal acquisitions for
cliff monitoring. By quantitative comparison of the results and validation by means of conventional
geostructural field surveys, the pros and cons of each method were outlined in attempt to depict the
conditions and goals the different techniques seem to be more suitable forRock slope failures in urban areas may represent a serious hazard for human life, as well as private and public property, even on the occasion of sporadic episodes. Prevention and mitigation measures indispensably require a proper rock mass characterization, which is often achieved by means of time-consuming, costly and dangerous field surveys. In the last decades, remote sensing devices such as high-resolution digital cameras, laser scanners and drones have been widely used as supplementary techniques for rock slope analysis and monitoring, especially in poorly accessible areas, or in sites of large extension. Although several methods for rock mass characterization by means of remote sensing techniques have been reported in specific studies, there are very few contributions that focused on comparing the different methods in an attempt to establish their advantages and limitations. With this study, we performed digital photogrammetry, Terrestrial Laser Scanning and Unmanned Aerial Vehicle surveys on a cliff located in a popular tourist attraction site, characterized by complex geological and geomorphological settings, as well as by disturbance elements such as vegetation and human activities. For each point cloud, we applied geostructural analysis by means of semi-automatic methods, and then compared multi-temporal acquisitions for cliff monitoring. By quantitative comparison of the results and validation by means of conventional geostructural field surveys, the pros and cons of each method were outlined in attempt to depict the conditions and goals the different techniques seem to be more suitable for
Implementation of InfraRed Thermographic surveys in complex coastal areas: the case study of Polignano a Mare (southern Italy)
Get PDFInfraRed Thermography (IRT) spread quickly during the second half of the 20th century in the
military, industrial and medical fields. This technique is at present widely used in the building
sector to detect structural defects and energy losses. Being a non-destructive diagnostic
technique, IRT was also introduced in the Earth Sciences, especially in the volcanology and
environmental fields, yet its application for geostructural surveys is of recent development.
Indeed, the acquisition of thermal images on rock masses could be an efficient tool for identifying
fractures and voids, thus detecting signs of potential failures.
Further tests of thermal cameras on rock masses could help to evaluate the applicability,
advantages and limits of the IRT technology for characterizing rock masses in different geological
settings.
We present some results of IRT surveys carried out in the coastal area of Polignano a Mare
(southern Italy), and their correlation with other remote sensing techniques (i.e. Terrestrial Laser
Scanning and Structure from Motion). The case study (Lama Monachile) is represented by a 20
m-high cliff made up of Plio-Pleistocene calcarenites overlying Cretaceous limestones. Conjugate
fracture systems, karst features, folds and faults, were detected in the rock mass during field
surveys. In addition, dense vegetation and anthropogenic elements, which at places modified the
natural setting of the rock mass, represent relevant disturbances for the characterization of the
rock mass. In this context, IRT surveys were added to the other techniques, aimed at detecting the
major discontinuities and fractured zones, based on potential thermal anomalies.
IRT surveys were carried out in December 2020 on the east side of the rock mass at Lama
Monachile site. Thermal images were acquired every 20 minutes for 24 hours by means of a FLIR
T-660 thermal imager mounted on a fixed tripod. Ambient air temperature and relative humidity
were measured during the acquisition with a pocketsize thermo-hydrometer. A reflective paper
was placed at the base of the cliff to measure the reflected apparent temperature. In addition,
three thermocouple sensors were fixed to the different lithologic units of the rock face. These
parameters, together with the distance between the FLIR T-660 and the rock face, were used in
order to calibrate the thermal imager and correct the apparent temperatures recorded by the
device, during the post-processing phase. Successively, vertical profiles showing the temperature
of the rock face over time were extracted from the thermograms. Thermal anomalies were
correlated with stratigraphic and Geological Strength Index profiles, obtained by means of field
surveys and Structure from Motion techniques. The presence of fracture and voids in the rock
mass was also investigated
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