1,720,960 research outputs found
Analisi tridimensionale agli elementi finiti di una frana in argille innescata da scavo al piede e verifica della strategia di mitigazione del rischio
No full textLe frane di prima attivazione di versanti in argille consistenti sature, innescate da scavo al piede
nel lungo periodo come conseguenza dei processi di consolidazione negativa delle pressioni interstiziali, sono
state nel tempo oggetto di numerosi studi. Una frana di questa tipologia ha interessato tra il 1980 ed il 1998 un
versante in argille pleistoceniche a nord della città di Lucera (Foggia). Lollino e coautori (2011) hanno presentato una interpretazione dettagliata dell’evoluzione tenso-deformativa del versante nel tempo fino al raggiungimento delle condizioni di collasso con l’ausilio di analisi bidimensionali. Nel presente lavoro è stato sviluppato un modello tridimensionale agli elementi finiti del versante nell’ipotesi di comportamento elasto-plastico drenato del terreno al fine di indagare l’evoluzione 3-D del processo di frana; ulteriori analisi numeriche sono state quindi condotte per verificare l’efficacia degli interventi di mitigazione del rischio messi in opera in anni recenti. I risultati del modello sono in accordo con le osservazioni di sito e confermano che la strategia di intervento adottata sia da considerarsi efficace rispetto all’obiettivo di stabilizzazione del versant
Multi-approach for the assessment of rock slope stability using in-field and UAV investigations
Full text linkThe present study is aimed at analyzing the rockfall phenomena involving a carbonate rock scarp in San Donato di Ninea village (Calabria, south Italy), where some buildings and a portion of a road are exposed to a high hazard condition. The geomechanical investigations of the rock scarp were performed through a multi-approach based on in-field investigations, geophysical surveys, and high resolution of images acquired by a drone. The achieved data allowed to assess the quality of the rock mass and the susceptibility of rock slope to failure through the Rock Mass Rating and the Slope Mass Rating clas sifications, respectively. The obtained results showed slope conditions ranging between unstable and completely unstable. Geophysical surveys allowed to investigate the subsurface material and showed a high jointing rock mass in the shallower portion. In order to acquire the potential change in geomechanical features on the whole escarpment rock, high-resolution images were acquired by a drone. Thus, a 3D dense point cloud model was reconstructed in a setting of high accuracy based on 55 million of points with a density of 748.85 points for m2. The 3D model was imported into CloudCompare software to extract the geological planes through FACETS plugin, which allowed to recognize the jointing sets on the whole surface of rock escarpment. The digital data were compared with the ones collected by scanline method in order to verify their soundness, and further detailed digital investigations were carried out on human inaccessible areas to examine the corresponding fracturing degree
The role of post-failure brittleness of soft rocks in the assessment of stability of intact masses: FDEM technique applications to ideal problems
Full text linkStrain-softening under low confinement stress, i.e. the drop of strength that occurs in the post-failure stage, represents a key factor of the stress-strain behavior of rocks. However, this feature of the rock behavior is generally underestimated or even neglected in the assessment of boundary value problems of intact soft rock masses. This is typically the case when the stability of intact rock masses is treated by means of limit equilibrium or finite element analyses, for which rigid-plastic or elastic perfectly-plastic constitutive models, generally implementing peak strength conditions of the rock, are respectively used. In fact, the aforementioned numerical techniques are characterized by intrinsic limitations that do not allow to account for material brittleness, either for the method assumptions or due to numerical stability problems, as for the case of the finite element method, unless sophisticated regularization techniques are implemented. However, for those problems that concern the stability of intact soft rock masses at low stress levels, as for example the stability of shallow underground caves or that of rock slopes, the brittle stress-strain response of rock in the post-failure stage cannot be disregarded due to the risk of overestimation of the stability factor.
This work is aimed at highlighting the role of post-peak brittleness of soft rocks in the analysis of specific ideal problems by means of the use of a hybrid finite-discrete element technique (FDEM) that allows for the simulation of the rock stress-strain brittle behavior in a proper way. In particular, the stability of two ideal cases, represented by a shallow underground rectangular cave and a vertical cliff, has been analyzed by implementing a post-peak brittle behavior of the rock and the comparison with a non-brittle response of the rock mass is also explored. To this purpose, the mechanical behavior of a soft calcarenite belonging to the Calcarenite di Gravina formation, extensively outcropping in Puglia (Southern Italy), and the corresponding features of the post-peak behavior as measured in the laboratory, have been used as a reference in this work, as well as the typical geometrical features of underground cavities and rock cliffs, as observed in Southern Italy, have been adopted for the simulations. The numerical results indicate the strong impact for the assessment of stability when rock post-peak brittleness is accounted for, if compared with perfectly plastic assumptions, and the need for adopting numerical techniques, as the FDEM approach, to take properly into account this important aspect of the rock behavior is highlighted
Brief communication: Monitoring a soft-rock coastal cliff using webcams and strain sensors
No full textIn this brief communication, we describe a case study about monitoring a soft-rock coastal cliff using webcams and a strain sensor, located in the Apulia region (south-eastern Italy). In this urban and touristic area, coastal recession is extremely rapid and rockfalls are very frequent. Using low-cost and open-source hardware and software, we are
monitoring the area, trying to correlate both meteorological information with measures obtained from the crack meter and webcams, aiming to recognize potential precursor signals that could be triggered by instability phenomena
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
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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