1,721,050 research outputs found
High resolution 3D geomechanical characterization for the evaluation of rockslide susceptibility scenarios
No full textAllo scopo di valutare gli scenari di rischio connessi a scivolamenti di roccia, si propone una metodologia integrata basata su rilievi in situ geologici e geomeccanici di dettaglio, e sull’utilizzo di tecnologie di remote sensing basate a terra quali il rilievo laser scanning (Terrestrial laser scanning=TLS) e la termografia ad infrarossi (Terrestrial Infrared Thermography=TIR). L’obiettivo della metodologia proposta è di ottenere una accurata caratterizzazione del versante roccioso investigato con le seguenti finalità: i) svolgere una dettagliata caratterizzazione geomeccanica 3D dell’ammasso roccioso; ii) individuare le porzioni di ammasso roccioso più critiche in termini di fenomeni di instabilità di versante; iii) calcolarne i volumi; iv) svolgere una dettagliata analisi di stabilità. In particolare è stato utilizzato un tool di Matlab (DiAna= Discontinuity Analysis) allo scopo di estrarre dati geomeccanici tridimensionali di dettaglio dalla nuvola di punti ad alta risoluzione ottenuta dal rilievo TLS. È stato inoltre eseguito un rilievo termografico per la valutazione qualitativa della filtrazione in corrispondenza delle discontinuità delimitanti le porzioni di ammasso roccioso più critici. L’integrazione fra le tecniche di remote sensing utilizzate ed i rilievi tradizionali in situ svolti, ha consentito di investigare settori di versante roccioso altrimenti non accessibili, restituendo una dettagliata caratterizzazione tridimensionale geometrica e geomeccanica dell’ammasso roccioso investigato, fornendo inoltre accurati parametri di input per l’analisi di stabilità
Effectiveness evaluation of flood defence structures in different geomorphological contexts
Full text linkThe flood risk in different geomorphological contexts of two less developed countries are investigated in order to evaluate the efficacy of the existing flood defence structures. In particular, a recent floodplain crossed by a wide meandering river and a narrow mountain valley flowed by creek with a torrential regime have been chosen for such analysis in North Albania and central Mexico, respectively. Both areas have been affected by disastrous floods in past years with considerable damages to properties and people. Some safety countermeasures have been performed over time, even if in a non-systematic way. For this reason, the current inclination to flood risk was assessed by means of a freeware software designed to perform one-dimensional (1D) hydraulic modelling for a full network of natural and anthropic channels (HEC-RAS software by Hydrologic Engineering Center River Analysis System). This new analyses take into account: i) the natural morphological variability along the river path, ii) the anthropic interventions on the fluvial dynamics, iii) the landscape appearance after the soil exploitation in the past years, and iv) all the changes induced by an exceeded informal urbanization. The reconstruction of the river and bordering areas geometric data was carried out according to the physical characteristics of the local environment: a bathymetric survey and near-river DGPS acquisitions for the open spaces of the Albanian floodplain, and traditional topographic methods for the highly vegetated Mexican valley. In both cases, the results show that the existing works are, on their own, poorly efficient in containing the predictable floods. Albanians levees seem underdimensioned, while the channelling works are too narrow to contain large amounts of water and solid transport as typical of the Mexican study area. Evidently, a new territorial planning is required in these areas, and some projects are now in place. However, it would be desirable that local authorities were profitably inspired by the criticalities here mentioned
Clean and renewable energy from the Arno River: A feasibility study in the Province of Florence (northern Italy)
No full textDuring a joint project between the Provincia di Firenze Administration and the Earth Sciences Department of the University of Firenze, the Arno riverbed was studied from the terminal portion of the Upper Valdano up to the Middle Valdarno (about 75 km). In particular, we analysed the preservation status of the existing weirs, which are nowadays the most important hydraulic works as concern the profile riverbed conservation and the fluvial dynamics. Such research was oriented to perform a practical analysis useful for a complete recovery of the hydraulic functionality and also for a possible renovation of some structures in order to produce clean electricity, following the current sensitivity in many national and international institutions. This analysis resulted in the determination of a different degree of feasibility, identifying from a technical point of view the most suitable weir and its annex for a quick recovery intervention and highlighting their economic impact on potential investors that might be attracted to the economic income related to the sale of electricity to the local network
A way forward to enhance the coping capacity of communities threatened by floods: The Dajç experience (Northern Albania)
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Runout modelling of gravity-induced pyroclastic density currents at Stromboli volcano (Italy)
No full textGravity-induced pyroclastic density currents (PDCs) at Stromboli volcano were investigated by means numerical and empirical modelling. With the aim of testing the suitability of landslide numerical model DAN- 3D and empirical models are used related to gravity-induced PDCs, in particular this work presents the results of the back analysis of three events occurred on 1906, 1930 and 1944 at Stromboli volcano. These two methods were able to reproduce the extension and the order of magnitude of the thickness of the PDCs reported in the literature. The best results of DAN-3D models were obtained using a Voellmy model with frictional coefficient of f = 0.19 and a turbulence parameter ξ = 1000 m/s. The mobility terms, find with the numerical model, are compared with empirical data of literature of the similar events
Residual slope stability in low order streams of angangueo mining area (Michoacán, Mexico) after the 2010 debris flows
No full textMexico, largely a tropical mountainous region, is continually subjected to natural hazards like landslides induced by heavy rainfalls. At the end of January 2010, two cold fronts and low-pressure storms moved over the State of Michoacán (central Mexico) and in February the town of Angangueo, in the eastern sector of the Monarch Butterfly Biosphere Reserve, was devastated by a huge muddy debris flow. The in situ observations after the event showed that considerable material was removed from the countryside surrounding the urban area. In this framework two low order streams were indicated as the main suppliers of granular material to the Angangueo River: Melon and Catingón creeks. To evaluate the residual risk and slope stability along these two torrential watercourses, specific investigations were carried out. A GIS-based map of the most relevant hazardous features was performed at high level of detail by means of targeted field surveys that distinguished natural and anthropogenic elements like: (i) riverbanks and slopes with new signs of instability and already collapsed areas; (ii) large accumulations of debris and plant remains in channels and slopes; (iii) deposits of mining waste and abandoned mining areas; (iv) hydraulic works along the riverbeds and (v) cultural elements potentially at risk. In both circumstances, a generalized criticality emerged; moreover, all the riverbanks along the Catingón creek are almost still under unstable conditions, whereas Melon creek has precarious riverbanks only for about 1/3 of the considered slopes. In both cases, the depth of their rupture surfaces seems directly related to the different geotechnical properties of existing materials with some influence from gradients
Application of infrared thermography for landslide mapping: The rotolon DSGDS case study
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Integrating back analysis and forward modelling of a debris flow with GB-InSAR data to assess the risk in a mountainous valley floor
No full textDebris flows are water-laden collapsing masses of soil and fragmented rocks. Those related to slope failures rush down mountainsides, funnel into stream channels and form thick deposits on valley floors. Usually, they are also associated with intense erosion along their path, that leads to a substantial increase in volume, runout distance, and disruptive energy. The prediction of landslide runout and its effect is essential in landslide risk assessment, especially in populated mountainous areas. In these areas, in fact, most human activities are concentrated in valley floors, that correspond to the areas most impacted by the flow. Both analytical and empirical methods can be employed to evaluate the runout extension. The 4th November 2010 debris flow event, detached from the Rotolon DSGSD detrital cover (Vicentine Pre-Alps, NE Italy) and channelized into the Rotolon creek riverbed, was modelled by means of DAN-3D numerical code. The debris flow travel distance was roughly 4 km, and many damages to hydraulic works and to four villages situated along the creek banks were reported. The back analysis of the 2010 runout showed that amongst all the available rheological kernels, the best one is the Voellmy-type. Varying the rheological reference parameters, in fact, the model could reproduce with high accuracy: i) debris flow impact area; ii) deposit thickness; iii) velocity; iv) final flow erosion volume. Based on the back analysis results, a forecasting analysis to assess the Rotolon valley exposure to possible future debris flow events was performed. Also this analysis was carried out by means of DAN-3D. i) The same input data of the back analysis; ii) a new possible source area (detected by means of GB-InSAR displacement data analysis); and iii) different thicknesses (hypothesized on the basis of the statistical analysis of the differences between the pre- and post-2010 event DTMs), were taken into account. These simulations produced impact area maps useful to evaluate the different future debris flow scenarios. The results showed that the integration of the modelling technique with ancillary data (such as detailed geomorphological and topographic maps, location and characteristics of the hydraulic works along the creek bed), together with the GB-InSAR-derived displacement maps, can be a very useful tool for the scientific community and local administrations to manage the problem related to debris flow events. This working method could also represent a standard procedure in cases of areas prone to different types of debris flow where also are available the GB-InSAR displacement monitoring system data. Nevertheless, the final reliability of the proposed method lies in the skill of expert operators regarding the choice of plausible volumes of possible future debris flow events
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