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Jaume Llopart Roger Urgeles Carl Fredrik Forsberg Angelo Camerlenghi Maarten Vanneste Michele Rebesco Renata Giulia Lucchi Denise Christina Rüther Hendrik Lantzsch 《Basin Research》2019,31(3):487-513
Using a combination of geophysical and geotechnical data from Storfjorden Trough Mouth Fan off southern Svalbard, we investigate the hydrogeology of the continental margin and how this is affected by Quaternary glacial advances and retreats over the continental shelf. The geotechnical results show that plumites, deposited during the deglaciation, have high porosities, permeabilities and compressibilities with respect to glacigenic debris flows and tills. These results together with margin stratigraphic models obtained from seismic reflection data were used as input for numerical finite element models to understand focusing of interstitial fluids on glaciated continental margins. The modelled evolution of the Storfjorden TMF shows that tills formed on the shelf following the onset of glacial sedimentation (ca. 1.5 Ma) acted as aquitards and therefore played a significant role in decreasing the vertical fluid flow towards the sea floor and diverting it towards the slope. The model shows that high overpressure ratios (up to λ ca. 0.6) developed below the shelf edge and on the middle slope. A more detailed model for the last 220 kyrs accounting for ice loading during glacial maxima shows that the formation of these aquitards on the shelf focused fluid flow towards the most permeable plumite sediments on the slope. The less permeable glacigenic debris flows that were deposited during glacial maxima on the slope hinder fluid evacuation from plumites allowing high overpressure ratios (up to λ ca. 0.7) to develop in the shallowest plumite layers. These high overpressures likely persist to the Present and are a critical precondition for submarine slope failure. 相似文献
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Acta Geotechnica - The increasing understanding of the connection between particle morphology and mechanical behaviour of granular materials has generated significant research on the quantitative... 相似文献
15.
Relations between hydrology and velocity of a continuously moving landslide—evidence of pore-pressure feedback regulating landslide motion? 总被引：1，自引：0，他引：1
We measured displacement, pore-water pressure, and climatic conditions for 3 years at the continuously moving Slumgullion
landslide in Colorado, USA. The landslide accelerated when pore-water pressure increased within the landslide body, but this
occurred as pore-water pressure decreased along the landslide margin. The decrease probably occurred in response to shear-induced
soil dilation at rates greater than pore-pressure diffusion and likely increased resistance to shear displacement and resulted
in landslide deceleration. This dilative strengthening has been experimentally observed and explained theoretically, but not
previously identified during field studies. Although landslide displacement should have exceeded that required to achieve
critical-state density of shear boundaries, observed relocation of these boundaries indicates that shearing is episodic at
fixed locations, so it permits renewed dilative strengthening when “fresh” soil is sheared. Thus, dilatant strengthening may
be a considerable mechanism controlling landslide velocity, even for landslides that have continuously moved great distances. 相似文献
16.
The scopes of this work are to study the mechanisms of load transfer and the deformations of the ground during slurry trenching and concreting in dry sand and to evaluate their effects on service structural loads, wall deflections and ground displacements behind the wall caused by subsequent excavation. A series of three-dimensional finite element analyses was carried out modelling the installation of diaphragm walls consisting of panels of different length. The soil was modelled as either linearly elastic-perfectly plastic or incrementally non-linear (hypoplastic) with elastic strain range. Plane strain analyses of diaphragm walls of identical cross section were also carried out in which wall installation was either modelled or the wall was wished in place (WIP). The analyses predict ground movements consistent with the experimental observations both in magnitude and trend. The results also show that the maximum horizontal wall deflections and structural loads reduce with increasing panel aspect ratio towards a minimum which is about twice the value computed for WIP analyses. Panel aspect ratios should be larger than about three to take advantage of the three-dimensional effects. The pattern and magnitude of surface vertical displacements obtained from linearly elastic-perfectly plastic analyses, no matter whether three- or two-dimensional, are unrealistic. 相似文献
17.
The walls of a deep excavation in cohesionless soils below the water table have been supported by a reinforced concrete diaphragm with T-shaped panels. To improve the safety against the risk of local collapse during the panel excavation, the soil surrounding the panels has been treated by deep mixing to a depth of 6?C10?m. The horizontal displacements, induced in the surrounding soil by the installation (deep mixing, slurry supported excavation, placing of the reinforcement cage, concrete casting and curing) of the diaphragm, have been measured by means of inclinometers. It is claimed that they can be a significant fraction of the total displacements induced by the excavation. A back analysis of the observed displacements shows that the deformation process is essentially elastic and can be satisfactorily modelled provided the values of the soil stiffness are properly selected. 相似文献
18.
Paganelli D Forni G Marchini A Mazziotti C Occhipinti-Ambrogi A 《Marine pollution bulletin》2011,62(8):1725-256
According to the European Water Framework Directive, the ecological status (ES) of a water body is determined by comparing observation data with undisturbed Reference Conditions (RCs). Defining RCs is crucial when evaluating the ES of a water body as it strongly affects the final outcome of any index application. Identifying RCs by observing real sites is not feasible in many marine environments, such as the Emilia-Romagna coast (Italy, N-Adriatic Sea). We used a statistical approach on a large dataset to derive RCs for the application of the benthic index M-AMBI in this area. We then applied M-AMBI to samples collected along a gradient of presumed environmental disturbance. The results put 14.8% of the Emilia-Romagna samples in “High” ES, 60.2% in “Good”, 23.0% in “Moderate” and 2.0% in “Poor”, showing a spatial gradient of improving quality. These results are in agreement with the extensive ecological knowledge available for this area. 相似文献
19.
Middle and late Pleistocene glaciations in the Campo Felice Basin (central Apennines, Italy) 总被引：1，自引：0，他引：1
The present paper refers to research conducted in the tectonic-karst depression of Campo Felice in the central Apennines (Italy), in which glacial, alluvial and lacustrine sediments have been preserved. Stratigraphic interpretations of sediments underlying the Campo Felice Plain are based on evidence obtained from nine continuous-core boreholes. The boreholes reach a depth of 120 m and provide evidence of five sedimentation cycles separated by erosion surfaces. Each cycle is interpreted as an initial response to a mainly warm stage, characterized by low-energy alluvial and colluvial deposition, pedogenesis, and limited episodes of marsh formation. In turn, a mainly cold stage follows during which a lake formed, and glaciers developed and expanded, leading to deposition of glacial and fluvioglacial deposits. The chronological framework is established by eleven accelerator mass spectrometer 14C ages and three 39Ar-40Ar ages on leucites from interbedded tephra layers. These age determinations indicate five glacial advances that respectively occurred during marine oxygen isotope stages 2, 3-4, 6, 10 and 14. 相似文献
20.
Cave clastic sediments as a tool for refining the study of human occupation of prehistoric sites: insights from the cave site of La Cala (Cilento,southern Italy) 
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