1,721,004 research outputs found
Shear mechanisms and viscoplastic effects during impulsive shearing
No full textIn clay formations, the co-seismic reactivation of preexisting landslides involves dynamic shear actions on sliding surfaces characterised by attritive states. Impulsive shear motions were applied, after the attainment of the fully softened and residual conditions, by means of an appropriately modified ring-shear apparatus. The kinematics parameters that characterise shear motions are related to co-seismic displacements of rigid landslide bodies, as defined by Newmark's approach. The results of the tests, performed on clay samples with different index properties, highlight the influence of the initial spatial disposition of particles on the shear mechanisms. In addition, it seems that these mechanisms control both the inviscid and viscous components of the shear stress. For high shear rates, an increase of the viscous strength in the residual condition determines a greater viscoplastic strength than that in the fully softened condition. On this basis, different behaviours in seismically induced reactivation of landslides can be explained
The 1998 Sarno landslides: Conflicting interpretations of a natural event
No full textLandslides affecting on 5-6 May 1998 the towns of Sarno, Quindici, Siano and Bracigliano in Southern Italy represent a case history of great significance both from a scientific and technical point of view. The casualties, the huge economic damage and the severe destruction attracted great attention on the part of the scientific community. Following the landslides, both the national and international scientific community and technicians have given rise to numerous studies in order to provide suitable elements for designing remedial works. From the scientific side, till 2010 hundreds of articles and reports were produced concerning researches carried out on the Sarno-type landslides. In order to make comparisons not only on different methodologies adopted but even on contrasting interpretations and results concerning landslide triggering and propagation mechanisms in a global and comprehensive picture of the knowledge, more than 200 scientific papers on this type of instabilities, published on national and international journals and conference proceedings, were collected. Analyses on specific aspects of the landsliding frequently show huge disagreements among different authors and research groups. The discussion particularly focuses on landslide classification aspects, criteria adopted and their real application. Wide-ranging ambiguities cause uncertainties in applying landslide classification criteria. © 2011 Casa Editrice Università La Sapienza
Methodology for seismic and post-seismic stability assessment of natural clay slopes based on a viscoplastic behaviour model in simplified dynamic analysis
No full textA co-seismic viscoplastic sliding model, composed of two consequential behaviour phases, was realised in order to assess the co-seismic and post-seismic stability of natural slopes. The model takes into consideration the development and distribution of available strengths in pre-seismic conditions, as well as the viscoplastic behaviours manifested during monotonic and impulsive fast shearing tests on different clayey soils. In relation to the strength increase produced by the shear displacement rate, phase I is present during sliding on pre-existing failure surfaces at the residual state and/or in weak bands at the fully softened state. In this latter case, this is limited to small displacements. Conversely, phase II is characterised by strength decrease and occurs if and when the inertial dynamic load mobilises the "impulsive critical shear strength", which is greater than the shear strength available in the pre-seismic static field. This implies the development of a first failure or a new failure surface with high shear displacements along these surfaces. The simplified dynamic analysis for infinite slopes, integrated by the behaviour model introduced in this paper, highlights a less conservative nature in comparison to that of the classic Newmark approach with one single exception. This occurs on attainment of the "static break point" where the co-seismic displacements obtained are comparable or even greater than those attainable from the classic Newmark approach. Furthermore, in relation to the co-seismic development of shear strength, it is possible to estimate in the short term as well as in the long term the post-seismic instability after the main shock. © 2011 Elsevier Ltd
Slope angle as indicator parameter of landslide susceptibility in a geologically complex area
No full textSlope angles are a key parameter in estimating susceptibility to developing earth flows. In this paper, slope angles are used to estimate potential unstable areas in a pilot sector of the Benevento province in (Southern Italy). Since the study area is characterized by a complex lithological setting, landslide distribution was analyzed within four-groups of homogeneous litho-technical sequences. Slope angle frequency distributions were obtained from a landslide sample in accordance with the Weibull probability density distribution function. Their analysis shows that the largest occurrence of landslides fall within an interval of slope angles ranging from 9 to 14. As filed surveys confirm, the low frequency of instabilities on steeper slopes can be explained by a deficit of potentially involving materials, partially due to the presence of stony sequences. Consequently, the probability of failure was calculated only on slope angle ranges already affected by existing landslide phenomena. © Springer-Verlag Berlin Heidelberg 2013
Combined monitoring of earth-flow movement and its environmental drivers, Montaguto earth flow in southern Italy
No full textWe investigated movement kinematics of the Montaguto earth flow and dynamic of its most active sector using data from GPS surveys and an instrumentation station. Residual movement of the flow was concentrated where the basal slip-surface form risers, where deep drainages are not installed and/or where springs fed man-made earth-flow creeks. Movement within the most active sector of the earth flow, the Body, was characterized by short-lived acceleration and deceleration driven by water-table-level variation during the spring, and by a slow-persistent movement interrupted by small surges, triggered by rapid rises of the water table caused by heavy rainfall during the winter. Our results improve the knowledge of the behavior of the Montaguto earth flow and might contribute to a better understanding of its future evolution. © Società Geologica Italiana, Roma 2016
Computational and experimental study of seismic site effects on Amatrice hill
No full textAmatrice is considered the town symbol of the destructive effects induced by 2016 Central Italy seismic sequence. As a result of the two main shocks (August 24th, M=6.0 and October 30th, M=6.5) the ancient urban area of the municipality, located on a hilly promontory, was heavily damaged. Old buildings, but also renovated and new buildings, suffered many cracks and collapses. Subsoil geological, geophysical and geotechnical data were collected in the area and seismic data were also available. By using and interpreting the subsoil data, a 3D-GIS model was developed, that is the basic geometrical model for SiSeRHMap hybrid-analysis. Several 2D sections crossing the seismic station sites were extracted from this model and analyzed by 2D-FEM numerical approaches. Comparison of numerical results and seismic experimental data allowed to: i) validate the subsoil model used in the simulations; ii) show the significant role of the topographic effects in the area under study; and iii) point out the variability of the 2D numerical results depending on the direction of the analyzed cross-sections
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
Structurally controlled earth flows of the Benevento province (Southern Italy)
No full textThe paper reports an investigation into the distribution and type of landslides in the Benevento province in southern Italy, between 2001 and 2008. Field mapping was undertaken at various scales up to 1:10,000 depending on the features identified. Landslide types were recognized within 5-group lithotechnical sequences cropping out in the province, grouped according to their similar mechanical and lithological features. The analysis showed a widespread diffusion of Earth Flows, with reactivation linked to both rainfall and seismic events. They are structurally controlled related to bedding, stratigraphic/tectonic contact between more and less competent sequences and a high degree of tectonisation. © 2010 Springer-Verlag
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