1,721,061 research outputs found
La Deformazione Gravitativa Profonda (DGPV) di Beauregard: Modellazione Numerica di Prove di Taglio
No full textIn particular I studied the deep-seated gravitational deformation recognized on the western slope of the stream named Dora di Valgrisenche, upstream of Valgrisenche (Aosta), and its interaction with the Beauregard arcgravity dam. A complete understanding of these DSGSD phenomena and their interaction with the Beauregard dam implies a correct definition of the geological-structural model and a geotechnical characterization of the affected materials. In order to test the cataclastic materials which come from the shear zone of the studied phenomena, the Multidisciplinary High Quality Laboratory DIPLAB (DIsaster Planning LABoratory) of the Structural and Geotechnical Engineering Department of the Politecnico of Torino, in collaboration with G.D.S. Instrument Ltd., developed a new direct shear test apparatus (High Pressure Back Pressure Shear Apparatus - HPBPSA) which allows to control the value of the pore pressure in the sample, simulating the rise of the groundwater level. To reproduce the functioning of HPBPSA, a numerical model was built, in order to simulate a direct shear test carried out with the High Pressure Back Pressure Shear Apparatus on the shear zone material of the Beauregard DSGSD. The numerical model, which was built with FLAC 5.0 (finite difference analysis), works accepting some simplified assumptions with respect to the experimental reality
How to model the stability of terraced slopes? : the case study of Tresenda (northern Italy)
No full textTerraces are very common morphological features all around the Mediterranean Basin. They have been built to adapt the natural morphology of the territory to the development of anthropogenic activities, particularly agriculture. However, the increasing land abandonment during the last century is leading to soil degradation and stability issues, mainly due to lack of maintenance of these peculiar environments. The objective of this study was to develop a coupled hydrologic-stability model to identify possible triggering areas of superficial landslides during intense rainfall events. The model was tested on a slope uphill of the village of Tresenda, in Northern Italy, which experienced several superficial landslides in the last 35 years. Distributed stability analyses are usually carried out using an infinite slope approach, but in the case of terraces some basic assumptions of this method fail: the parallelism between topographical surface and potential sliding surface and the high ratio between slope length and failure surface depth are the most important examples. In addition, the interest is more on the stability of the terrace system (dry stone retaining wall and backfill soil) and
not on soil alone. For these reasons, a stability analysis based on the global method of equilibrium is applied and soft coupled to a well know hydrological model (STARWARS). Sections of terrace, one cell wide, are recognized from the base of a wall to the top of the closest downstream one, and each cell (1 x 1 m2) is considered as a slice. The method of Sarma for circular and non-circular failure is applied. The very fine horizontal resolution (1 m) is crucial to take into consideration the hydrogeological and mechanical properties of dry stone walls (0.6-1.0 m wide). A sensitivity analysis was conducted for saturated water content, initial volumetric water content, the cohesion and friction angle of soil and walls and soil depth. The results of the sensitivity analysis showed that instability never occurs if less than 60% of the soil depth is saturated. In addition, a variation of 10% in the cohesion and friction angle of soil leads to changes in critical acceleration (factor of safety) of 4%
and 5%, respectively. On the other hand, a variation of 10% in wall cohesion and friction angle leads to changes in the critical acceleration of around 4% and 1.5%, respectively. The use of a soil depth map with slightly different depths caused a different distribution in the number and location of instabilities. This underlines how this parameter, which is difficult to determine at high resolution, plays a central role in controlling location and volume of potential unstable masses. The model was finally evaluated on historical events and it demonstrated to be a good and reliable instrument to reproduce water levels and localise the most critical area for the triggering of superficial landslides on terraced slopes. In detail, field-measured water levels are modelled with a normalized RMSE of about 10%. Regarding stability, the triggering areas of the two superficial landslides occurred in May 1983 were well reproduced both temporally and spatially
Parametrization of a dry retaining wall on a terraced slope in Valtellina (Northern Italy) and stability analysis
Full text linkThe mechanical characterization of dry retaining walls is a key issue for the stability analysis of slopes in Valtellina, where vineyard cultivated terraces have already been involved in rapid mass movements. The study presents the solution adopted to approach the problem by numerical modelling, focusing on the difficulties in the parameterization of dry walls.
While geotechnical field and laboratory measurements allowed to define the backfill soil properties following conventional procedures, no standards are proposed for dry walls. The walls are likened to equivalent rock masses, where blocks with different shapes and dimensions, are separated by “discontinuities” characterized by aperture, filling and roughness. Direct observations and images analysis allowed to assign to the walls a Geological Strength Index, applying the Hoek & Brown criterion, and to calculate the wall equivalent values of cohesion and friction angle.
The performed stability analysis is supported by a previous hydrological model, which allows to define a temporary perched groundwater level when a rainfall is simulated. The infiltration phase has been calibrated and validated comparing the in situ water levels, recorded by continuous piezometric datalogger, with the simulated ones, using as input rainfalls registered with a meteorological station. Then two different rainfall scenarios, with similar duration and return period, are reproduced: the first caused three mass movements in 1983 while the second had no instability consequences. Once the hydrological models have been reconstructed, the stress-strain modeling is performed to verify the worth of the geomechanical parameters assigned to the wall, and eventually calibrate them.
The present work emphasizes the importance of direct measurements and monitoring activities to develop reliable conceptual models for numerical analysis of groundwater flow and stability in an anthropogenic impacted geological context. Moreover it highlights the importance of field measures to reduce the uncertainty of parameters that are almost impossible to be measured directly
Modeling the stability of terraced slopes: an approach from Valtellina (Northern Italy)
No full textThis study focuses on the relationships between hydrological processes and the stability of terraced slopes. Emphasis is given to the presence of dry-stone retaining walls and how to explicitly consider them when performing a distributed stability analysis. Valtellina, an Alpine valley of Northern Italy, is selected as study area. In detail, the slope uphill the village of Tresenda, affected by several superficial landslides since 1983, is studied. Dry-stone walls heavily influence the hydrological and geotechnical processes at the slope scale, and it is therefore crucial to consider them when performing a stability analysis on mountainous terraced areas. Walls are usually 0.60–1.00 m wide, and therefore, base maps (Digital Elevation Models and soil depth map) with a horizontal resolution of 1 m have been appositely derived. Working at this horizontal resolution leads to the failure of some basic assumptions of the infinite slope method, usually applied for distributed stability analysis. In this study, we propose an alternative approach based on the global method of equilibrium applied to sections of single terraces one cell wide. A specific sensitivity analysis allowed to fix some constrains to the model, in order to improve the reliability of the results under different mechanical and hydrological conditions. The proposed stability model was calibrated and evaluated on recorded past rainfall events. It resulted to be a good instrument for the identification of the most unstable areas when stressed with high pore-water pressure conditions
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Relazioni tra precipitazioni e sviluppo di falde sospese in versanti terrazzati
Full text linkIl lavoro vuole contribuire alla comprensione delle dinamiche di infiltrazione e circolazione idrica, in un versante terrazzato con muretti a secco, per capire i meccanismi di formazione di falde sospese temporanee,i il loro rapporto con gli eventi di precipitazione e con la stabilità dei muri. Sulla base di dati di precipitazione e misure piezometriche recenti è stata proposta una soglia pluviometrica di sviluppo di falde sospese e un’analisi degli eventi meteorologici dal 1980 ad oggi. Si è poi costruito un modello numerico che riesce a riprodurre la formazione e lo sviluppo di falde sospese sul versante
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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