186,186 research outputs found
Stability analysis of an active marble quarry by DEM modelling
No full textThe marble quarry herein considered is located in the Apuan Alps (Italy), at the base of a deep gully cut by vertical walls, reaching a height of 180 m. The rock mass is cut across by different discontinuity sets, whose spacing is generally wide. The various sets significantly differ in persistency and thus affect the overall strength. In this paper the stability of a plane section of a typical steep face is studied by the Distinct Element Method. The stress-strain behaviour of the discontinuities is represented by the Barton-Bandis model and the presence of rock bridges is explicitly accounted for. The influence of different lengths of rock bridges and spacings on the overall stability was investigated by means of sensitivity analyses. Three different indexes were adopted to synthetically represent the severity of the stress state in the successive stages of excavation. Comparison among such parameters highlights similar trends as the excavation advances, thus indicating that the three indexes generally provide a “measure” of stability. The quarry faces exhibit a very limited amount of displacement and stability is obtained in each of the excavation steps
Analisi delle condizioni di sicurezza di una cava in esercizio con modelli del discontinuo. Memorie Gruppo Naz. Ing. Geotec
No full textAnalisi delle condizioni di sicurezza di una cava in esercizio con modelli del discontinuo
No full textEmpirical and numerical analysis of the blast - induced structural damage in rock tunnels
No full textOne of the main hazards in rock tunneling by using the drill and blast method is the damage of the nearby pre-existing underground structures due to ground vibrations generated by the explosion. A simplified empirical approach is commonly adopted for the assessment of blast - induced structural damage, based on the peak particle velocity (PPV) and related empirical threshold values. A more sophisticated approach consists in numerical analysis of rock – sup-port interaction under the dynamic load induced by blasting. This allows evaluate ground vibrations and internal forces inside the underground structures. Both approaches are applied in the present paper for evaluating the feasibility of a drill and blast tunnel excavation in the vicinity of a pre-existing tunnel. Based on the presented results, it is possible to conclude that the simplified empirical approach significantly overestimates the risk of the blast - induced structural damage compare to the numerical stress analyses
Analysis of convergence data and 3D numerical modelling of tunnels excavated in fine-grained soils
No full textThis paper focuses on the convergence measurements of twin motorway tunnels under excavation in a Pliocene formation in the South of Italy. The tunnels are driven full face, with a cross-section of 120 m(2), by means of a conventional excavation method, up to a maximum depth of 120 m. The primary lining is an open arch made up of shotcrete and steel sets; the definitive lining consists of concrete cast in three different stages. Convergence measurements were analyzed on the basis of the curve-fitting technique proposed by Sulem et al. (1987). Then, the influence on tunnel deformation of overburden and lining construction sequence is investigated. Finally, the role of the primary and final linings in reducing tunnel convergence is investigated by means of a three-dimensional stress-strain analysis, performed with FLAC3D code
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
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