Seismic tomography imaging of an unstable embankment     

Gian Piero Deidda  Gaetano Ranieri 《Engineering Geology》2005,82(1):32-42

Seismic tomography imaging was employed to make a diagnosis and choose a remedy for an embankment supported by a retaining wall showing clear evidence of structural instability. The geometry and structural characteristics of the wall, the inside geometry of cracks, and the physical parameters of the underground materials were the primary objectives of the geophysical survey. Seismic data were acquired along two vertical sections each one delimited by the lines of the sources within an inclined borehole and of the receivers lying on the ground. For each section, a total of 744 travel times were inverted to obtain compressional-wave velocities on a regular rectangular grid of squared cells (1 m × 1 m) using an inversion algorithm which is based on the simultaneous iterative reconstruction technique (SIRT). Ultrasonic tests carried out in laboratory on intact specimens, together with other supplemental site information, improved tomography resolution, allowing global and node constraints that forced the solution of the inverse problem to match known boundary values. Tomography imaged two high-velocity zones separated by a curved-shape low-velocity zone. The first ones were found to be compatible with the concrete retaining wall and with the schist materials, ranging from highly weathered to intact schist, while the low-velocity zone was interpreted as filling materials and/or completely decomposed rock schist. The combination of seismic tomography and laboratory measurements allowed extrapolation of important parameters over a large volume of rock mass, otherwise only representative of small rock samples near boreholes. It also enabled engineering characterization of subsurface rock mass, providing useful and accurate information to design a remedy for the embankment.  相似文献   

The Newmark scheme as velocity–stress time-staggering: an efficient PML implementation for spectral element simulations of elastodynamics     

Gaetano Festa  Jean-Pierre Vilotte 《Geophysical Journal International》2005,161(3):789-812

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A multi-disciplinary study of the 2002–03 Etna eruption: insights into a complex plumbing system     

Daniele Andronico  Stefano Branca  Sonia Calvari  Michael Burton  Tommaso Caltabiano  Rosa Anna Corsaro  Paola Del Carlo  Gaetano Garfì  Luigi Lodato  Lusia Miraglia  Filippo Murè  Marco Neri  Emilio Pecora  Massimo Pompilio  Guiseppe Salerno  Letizia Spampinato 《Bulletin of Volcanology》2005,67(4):314-330

The 2002–03 Mt Etna flank eruption began on 26 October 2002 and finished on 28 January 2003, after three months of continuous explosive activity and discontinuous lava flow output. The eruption involved the opening of eruptive fissures on the NE and S flanks of the volcano, with lava flow output and fire fountaining until 5 November. After this date, the eruption continued exclusively on the S flank, with continuous explosive activity and lava flows active between 13 November and 28 January 2003. Multi-disciplinary data collected during the eruption (petrology, analyses of ash components, gas geochemistry, field surveys, thermal mapping and structural surveys) allowed us to analyse the dynamics of the eruption. The eruption was triggered either by (i) accumulation and eventual ascent of magma from depth or (ii) depressurisation of the edifice due to spreading of the eastern flank of the volcano. The extraordinary explosivity makes the 2002–03 eruption a unique event in the last 300 years, comparable only with La Montagnola 1763 and the 2001 Lower Vents eruptions. A notable feature of the eruption was also the simultaneous effusion of lavas with different composition and emplacement features. Magma erupted from the NE fissure represented the partially degassed magma fraction normally residing within the central conduits and the shallow plumbing system. The magma that erupted from the S fissure was the relatively undegassed, volatile-rich, buoyant fraction which drained the deep feeding system, bypassing the central conduits. This is typical of most Etnean eccentric eruptions. We believe that there is a high probability that Mount Etna has entered a new eruptive phase, with magma being supplied to a deep reservoir independent from the central conduit, that could periodically produce sufficient overpressure to propagate a dyke to the surface and generate further flank eruptions.Editorial responsibility: J. Donnelly-Nolan  相似文献   

The Tsenkher structure in the Gobi-Altai, Mongolia: Geomorphological hints of an impact origin     

Goro Komatsu  John W. Olsen  Jens Orm  Gaetano Di Achille  David A. Kring  Takafumi Matsui 《Geomorphology》2006,74(1-4):164-180

The Tsenkher structure, in the Gobi-Altai region of Mongolia, was studied using a wide array of remote sensing data and field observations. The structure has a shallow, 3.6 km wide, central depression bordered by a near-circular ridge (putative crater rim) with breaches to the northwest. The central depression is obliterated partially by fluvial infill through these breaches. Outside the ridge, the western side is a rugged terrain, but the eastern half is characterized by a concentric outer ridge that occurs at about one radius distance from the inner ridge. Although intrusion, salt tectonics and maar crater hypotheses cannot be completely ruled out, its morphology strongly implies an impact origin for the Tsenkher structure. If of impact origin, it has a well-preserved morphology and its position in the basin fills indicates that the formation may have occurred relatively recently, sometime during the late Tertiary or Quaternary. The outer ridge morphology is similar to rampart craters on Mars, whose formation has been attributed to fluidization of a water-rich target layer and ejecta materials, or to atmospheric entrainment and deposition of ejected materials. However, other hypotheses including erosional remnant of ejecta blanket, erosional scarp of structural rim uplift, multi-ring or deeply eroded crater rim of a peak-ring crater are also possible at this stage. A complex fluvial and probable lacustrine history is envisaged within the Tsenkher structure. The structure is also associated with archaeology, including Paleolithic and Bronze Age remains.  相似文献   

Solar internal rotation and dynamo waves: A two-dimensional asymptotic solution in the convection zone     

Gaetano Belvedere  Kirill Kuzanyan  Dmitry Sokoloff 《Journal of Astrophysics and Astronomy》2000,21(3-4):379-380

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A model-order reduction framework for hybrid simulation based on component-mode synthesis     

Gaetano Miraglia  Milos Petrovic  Giuseppe Abbiati  Nebojsa Mojsilovic  Bozidar Stojadinovic 《地震工程与结构动力学》2020,49(8):737-753

Testing of stiff physical substructures (PSs) still poses major technical issues that prevent from adopting hybrid simulation (HS) as a standard structural testing method. Firstly, elastic deformation of reaction frames, as well as the limited resolution of displacement transducers, deteriorate displacement control accuracy. Secondly, as a consequence of control errors, small perturbations of actuator displacements entail large restoring force oscillations that spuriously excite the higher eigenmodes of the hybrid model. For this reason, in the current practice, force-controlled hydraulic jacks handle vertical degrees of freedom, which are typically associated with stiff axially loaded members and excluded from the time integration loop. Vertical forces are either kept constant or adjusted during the experiment based on simplified redistribution rules. Besides deterioration of displacement control accuracy, stiff PSs naturally increase the frequency bandwidth of the hybrid model, whose higher eigenfrequencies (divided by the testing time scale) may fall outside the frequency bandwidth of the actuation system, thus destabilizing the HS. This is a collateral issue to which, in the authors' knowledge, no sufficient attention as been dedicated yet, and this paper tries to address it. From this standpoint, we propose component-mode synthesis as a rigorous approach for deriving reduced-order physical and numerical substructure mass and stiffness matrices that minimize the frequency bandwidth of the hybrid model. The proposed methodology allowed for performing HSs of a load-bearing unreinforced masonry structure including both horizontal and vertical degrees of freedom with a standard three-actuator setup used for cyclic testing.  相似文献   

Shake table tests on standard and innovative temporary partition walls          下载免费PDF全文

Crescenzo Petrone  Gennaro Magliulo  Gaetano Manfredi 《地震工程与结构动力学》2017,46(10):1599-1624

Shake table tests are performed on temporary internal partitions for office buildings. Four different specimens are tested. A steel frame is designed to exhibit relative displacements which typically occur at a given story of ordinary buildings. Four different partition walls are tested simultaneously for each specimen typology. This allows investigating the influence of an innovative device on the seismic performance of the tested components. The innovative device avoids the unhooking of the panels from the supporting studs. Several shake table tests are performed subjecting the specimens to interstory drift ratios up to 1.57%. Both the hysteretic curves and the natural frequency trend highlight that the partitions do not contribute to the lateral stiffness of the test setup. The damping ratio increases after the partition walls are installed within the test frame, causing a beneficial effect in the dynamic response. Minor damage state occurs for interstory drift ratio (IDR) in the range 0.41–0.65% in standard specimens, whereas moderate and major damage states are attained for IDR in the range 0.51–0.95%. Significant increase of collapse IDR is recorded with the introduction of the innovative device, up to IDR larger than 1.45%. It can be therefore concluded that a simple innovative device is defined, which significantly improves the seismic performance of the tested specimen. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Starved versus alluvial river bedforms: an experimental investigation     

Gaetano Porcile  Paolo Blondeaux  Marco Colombini 《地球表面变化过程与地形》2020,45(5):1229-1239

Laboratory experiments were conducted to investigate the formation of river bedforms under sediment supply-limited conditions, i.e. when a motionless substratum is bared by the dynamics of the mobile sediments. Three series of experiments were organized in a laboratory flume by fixing all the hydrodynamic and morphodynamic parameters but varying the thickness of the initial layer of mobile sediments which covers the rigid bottom of the flume. At the end of all the experiments, which lasted for the same amount of time, the formation of transverse sand dunes was observed. For decreasing , the rigid bottom of the flume was bared progressively earlier during the experiment and the measurements showed a clear tendency of the bedforms to lengthen, i.e. to increase their crest-to-crest distance. Moreover, under strong supply limitation, the two-dimensional transverse dunes turned into three-dimensional barchanoid forms and into isolated barchan dunes characterized by an abrupt reduction in bedform heights. A two-dimensional Fourier analysis of the bottom profile was performed, providing the amplitude of the main streamwise and spanwise harmonic components of the bottom morphology as a function of . © 2019 John Wiley & Sons, Ltd.  相似文献   

Parametric study on seismic ground response by finite element modelling     

Angelo Amorosi  Daniela Boldini  Gaetano Elia 《Computers and Geotechnics》2010

In this paper the results of 2D FE analyses of the seismic ground response of a clayey deposit, performed adopting linear visco-elastic and visco-elasto-plastic constitutive models, are presented. The viscous and linear elastic parameters are selected according to a novel calibration strategy, leading to FE results comparable to those obtained by 1D equivalent-linear visco-elastic frequency-domain analyses. The influence of plasticity on the numerical results is also investigated, with particular reference to the relation between the hysteretic and viscous damping effects. Finally, different boundary conditions, spatial discretisation and time integration parameters are considered and their role on the FE results discussed.  相似文献   

Non-life insurance consumption in Italy: a sub-regional panel data analysis   总被引：1，自引：0，他引：1  

Giovanni Millo  Gaetano Carmeci 《Journal of Geographical Systems》2011,13(3):273-298

We analyze the consumption of non-life insurance across 103 Italian provinces in 1998–2002 in order to assess its determinants, in the light of the empirical literature. Using sub-regional data, we overcome an important limitation of cross-country analyses, i.e. the systemic heterogeneity due to country-specific characteristics. Individual heterogeneity is accounted for through panel data techniques. However, considering spatial units within a single market raises issues of cross-sectional or spatial dependence, either due to common nationwide and/or regional factors or to spatial proximity. We carefully assess spatial dependence, employing recent diagnostic tests, finding out that the regressors included in our specification successfully account for spatial dependence. Insurance turns out to depend on income, wealth and some demographics, as already established, but also on trust, judicial efficiency and borrowing conditions. These findings help in explaining the gap between Central-Northern Italy and the south of the country.  相似文献