1,721,005 research outputs found
Evoluzione geologico-ambientale e storia vitivinicola nel Delta del Po.
No full textDiscussione dei rapporti fra l'evoluzione idrografico deposizonale, la storia paleoclimatica, l'evoluzione paleambientale e la storia eno-viticola del delta padano e della pianura ferrarese
Down-hole geophysical characterization of middle-upper Quaternary sequences in the Apennine Foredeep, Mirabello, Italy
No full textThe 2012 earthquakes sequence stroke a wide area of the alluvial plain in the Emilia-Romagna Region and triggered a new research interest on the role of the subsurface stratigraphic architecture and petrophysical property distribution in the modulation of the local seismic effects. Few direct shear wave velocity VS data were however available below the depth of 50 m. The only available VS measurements were obtained from an anticline area, characterized by a reduced stratigraphic thickness and peculiar sedimentary facies, hardly representative of the majority of the alluvial plain
subsurface. The study provides the first VS profile available from middle-upper Quaternary successions deposited into a fast subsiding syncline area of the Apennine Foredeep Basin. The P-wave velocity VP and the S-wave velocity VS logs fill in the previous data gap on the geophysical parameters needed for the estimation of the local seismic response. Both VP and VS logs were continuously acquired to the depth of 265 m. The log records a velocity increase with depth, punctuated by sharp increases at some stratigraphic discordance surfaces. The value of 800 m/s that characterizes the “seismic bedrock”, as defined by the Italian building code [NTC 2008] was never reached at any depth. The investigated succession records a depositional evolution from deltaic-marine to alluvial plain conditions, punctuated by six glacio-eustatic depositional cycles, developed in Middle-Upper Quaternary times. The stratigraphic units described in the syncline log were correlated at a regional scale, with the thinner anticline succession of Mirandola. Correlatable units deposited into syncline and anticline areas reveal similar shear wave velocity values, supporting the regional extrapolation of the measured values
Pratiche correnti per le analisi di suscettibilità alla liquefazione negli studi di microzonazione sismica di livello 3
No full textQuadro di sintesi delle prove di laboratorio eseguite sui campioni di terreno liquefatto a seguito del terremoto del 29 dicembre 2020 a Petrinja (Croazia)
No full textRisposta sismica locale a supporto della microzonazione sismica: il caso di Pietracamela (Appennino Centrale)
No full textValorizzazione turistica di geo-bio-topi della Pianura del Po tramite tecniche di GIS mobile interattivo e WEB-GIS: i progetti pilota di Bosco Mesola e della Foresta della Panfilia.
No full textLiquefaction-Induced Downdrag on Tapered Piles from Full-Scale Blast Liquefaction Tests
No full textFrequently, deep foundations extend through potentially liquefiable sand layers near the ground surface and bear on more competent layers at depth. When liquefaction occurs, the skin friction in the liquefied layer would be expected to decrease to some negligible value, but as the liquefiable layer settles, negative skin friction could potentially develop around the pile in this layer as effective stress increases. To investigate the loss of skin friction and the development of negative skin friction, axial load tests were performed on an instrumented full-scale tapered pile before and after blast-induced liquefaction at a site in Mirabello (Ferrara, Italy) that was affected by liquefaction following the 2012 Emilia earthquakes. The test pile was a 16.5 m long concrete pile with a diameter of 0.52 m at the head tapering to 0.26 m at the toe. Following blasting, liquefaction developed within a 6-m thick sand layer below a clay surface layer resulting in significant settlement. Skin friction in the liquefied layer initially dropped to essentially zero. However, as the liquefied sand reconsolidated, negative skin friction became equal to about 50% of the pre-blast ultimate positive skin friction. Negative skin friction in the overlying non-liquefied clay layer was only 80% of the ultimate positive skin friction. This is likely due to the surrounding soil moving slightly away from the tapered pile as the soil settled vertically downward. Despite significant ground settlement, pile settlement was relatively small because of the resistance provided by the toe of the pile
Characterization of soil deformation due to blast-induced liquefaction by UAV-based photogrammetry and terrestrial laser scanning
No full textSoil liquefaction due to an earthquake can lead to permanent soil deformation and reduction of load-bearing capacity that in turn could act on building stability. Since a quantitative evaluation of post-liquefaction settlements is often very difficult, field scale liquefaction tests, carried out under controlled conditions, such as blast tests, are used to perform a correct quantitative analysis of the liquefaction phenomena. Among the significant parameters related to a blast test, there are the geometric ones, i.e. the extension of the area affected by the blast-induced liquefaction and the corresponding vertical displacements. This article shows the results of a blast test carried out at a trial site located in Mirabello (Ferrara, Italy) from a remote-sensing perspective. Data provided by aerial Structure-from-Motion photogrammetry, supported by terrestrial laser scanning measurements, were used to evaluate the soil deformation that, in the specific case study, aided a geological/geotechnical interpretation of the blast test results. In general, the proposed method can be used to characterize areas affected by blast-induced liquefaction, including those cases where blasting is used as ground improvement technique aimed at mitigating the seismic hazard
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