1,721,015 research outputs found
Anisotropic dilatant behavior of rock fractures
No full textAmong the constitutive models for rock fractures developed over the years, Barton's empirical model has been widely used because it is easy to apply and includes several important factors associated with fracture characteristics. Different researchers investigated anisotropic behavior of rock joints experimentally. They proposed models that can deal with the strength, deformability, or dilatancy of rock fractures. These models include several parameters and they are much more complicated than Barton's model. Experimental data found in the literature are used in this paper to formulate a method to simulate anisotropic behavior of rock fractures in accordance with Barton's model. The shear strength, shear stiffness, and dilation displacement of rock fractures subjected to shearing in all directions can be predicted using the proposed model applied on Barton's failure criterion parameters. © 2012 American Society of Civil Engineers
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
Validation of a Modified Barton method and its use in numerical analysis for the stability valuation of key blocks in rock tunnels
No full textThis study, conducted at "The University of Texas at Austin" thanks to a joint research project with the Turin Polytechnic, concerns the effect of dilatancy on the stability of keyblocks in rock tunnels. This topic has been addressed from two point of view: - an experimental part to analyzed and validate a modified Barton's model to supplement some weakness points in the original Barton's model; - an analytic part to apply the modified Barton's model to evaluate the stability of keyblocks in rock tunnels. The advantages achieved through the adjustments of the Barton's model are validate from laboratory tests on four different rock types: limestone, sandstone, granite and metamorphosed limestone. The laboratory tests are Point Load Test, Schmidt hummer test, Uniaxial Compression Test, Direct Shear Test on sawed and rough artificial discontinuities. The elaborate continues with numerical simulations, conducted using an algorithm called "BS3D" (Tonon & Asadollahi, 2008) to evaluate the stability of keyblocks of different shapes at the rock tunnels boundary. The final considerations indicate that the modified Barton's model guaranties better approximations of the stress vs horizontal displacement graphs while the vertical displacement vs horizontal displacement graphs are predicted in an approximate way either through the Barton's model and the modified model. The modified Barton's model guaranties the best estimates of the peak shear displacement. At the end the numerical analysis show that the in situ stress is the geomechanical parameter that greater influences on the factor of safety
Validazione di un metodo di Barton Modificato e relativo utilizzo nelle analisi numeriche per la valutazione della stabilità di blocchi chiave in gallerie in roccia
No full textLo studio tratta l'effetto della dilatazione sulla stabilità di blocchi chiave in gallerie in roccia mediante lo sviluppo di un nuovo metodo analitico e prove di laboratorio dedicat
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
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