1,720,976 research outputs found
Finite element simulations of twin shallow tunnels
No full textUnlike for deep tunnels, prediction of displacements represents a key factor when analyzing tunnel excavation with low overburden, not only for defining the influence of the excavation on preexisting structures but also for providing a basis to put the observational method in place. The accurate assessment of the deformations induced by tunneling is strongly dependent on the choice of the appropriate constitutive model and on the parameter calibration against experimental data.
The case study presented in this paper deals with the construction works of a new highway in Southern Italy, including five twin tube shallow tunnels. Considering that two-dimensional analyses are usually not able to reproduce simultaneously all the aspects of the stress-strain response due to tunneling, three-dimensional finite element analyses were performed in order to compare the results of the numerical analysis with the monitoring data. The available database includes a wide range of displacement and deformation measurements
Numerical analyses of stability and deformation behavior of reinforced and unreinforced tunnel faces
No full textIn traditional tunneling, an analysis of the face stability is required to avoid failure mechanisms or excessive face extrusion. Face reinforcement can improve face stability and reduce deformations. In the present work a numerical study of both unreinforced and reinforced tunnel excavation faces by means of 3D FEM analyses is presented. The results are compared with those of the traditional limit equilibrium method and with an analytical solution based on previous numerical studies. It could be shown that the LEM may lead to non-conservative results. Finally, the deformation response is assessed and the benefits of face reinforcements are investigated
Comparisons of Eurocodes design approaches for numerical analysis of shallow tunnels
Full text linkAlthough Eurocode 7 is not meant to be applied to the design of tunnels, the lack of standard codes explicitly focusing on tunneling leads to the situation that it is increasingly used in practice, at least for shallow tunnels in soil. However, there is no general agreement on which of the approaches defined in EC7 is the most suitable for the design of shallow tunnels, in particular when it comes to applying them in combination with numerical analyses. In this paper, the results of numerical calculations aimed at assessing ultimate limit state conditions of a shallow tunnel in soil are presented. The focus of the present work is firstly on the verification of the applicability of the Eurocodes in combination with numerical analyses and the comparison of different design approaches. Secondly, the consequences of the choice of a nonlinear material model for the shotcrete primary lining are discussed
Slope Safety Factor Calculations With Non-Linear Yield Criterion Using Finite Elements
No full textThe factor of safety for a slope is calculated with the finite element method using a non-linear yield criterion of the Hoek-Brown type. The parameters of the Hoek-Brown criterion are found from triaxial test data. Parameters of the linear Mohr-Coulomb criterion are calibrated to the same triaxial data and the corresponding safety factor is calculated. Of the two safety factors the Hoek-Brown factor is the lower. Triaxial tests carried out with a wide stress range indicate that the failure envelope of soils is indeed non-linear, especially at low confinement stresses. As standard triaxial tests are carried out at much higher stress levels than present in a slope failure, this leads to the conclusion that the use of the non-linear criterion leads to a safer slope desig
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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