2,257 research outputs found
Influence of initial conditions on the liquefaction strength of an earth structure
No full textLiquefaction has been the major source of damage for structures and infrastructures in most recent earthquakes, as it induces loss of strength and stiffness in soils, resulting in settlement of buildings, landslides, and failure of pipelines and earth dams. Such a phenomenon is primarily associated with saturated cohesionless soils and strong-motion seismic events able to induce pore water pressure build-up. Even though the degree of soil saturation is strictly related to the oscillation of groundwater table and to the interaction flows (namely precipitation and evaporation) between the exposed surface and the atmosphere, the initial distribution of pore water pressure is commonly simplified in liquefaction potential analysis and the presence of unsaturated soil layers is almost always neglected. To try to fill this gap, this work investigates the effect of the initial distribution of pore water pressure on the liquefaction strength evaluation, considering the potential presence of unsaturated soil layers. The work uses as case-study a well-investigated inhabited levee damaged by the 2012 Emilia earthquake. The initial distribution of pore water pressure within the dyke is carried out by solving the Richards equation in steady-state and transient conditions, assuming as boundary conditions the evolution of potential flows recorded at the site in the time period including the earthquake event. The cyclic resistance of unsaturated soils is considered during the execution of dynamic analyses in effective stress conditions. Results of the analyses show that initial conditions influence the liquefaction strength of earth structure and that neglecting the cyclic resistance of unsaturated soils is not a conservative assumption
Differences in results yielded by different approaches adopted for the interpretation of a rapid flowslide in a pyroclastic cover
No full textThe paper interprets a case-history of rainfall-induced flow-like landslide in pyroclastic soils by adopting different approaches inmodelling the boundary value problem. In particular, two adopted approaches take into account both rainfall and evaporation effects, while the simplest one disregards the phenomenon and considers only the effects of the rainfall-history. The work shows how increasing model complexity in accounting for most of influencing meteorological factors permits predicting a more pronounced hydrological singularity at the landslide tim
Two Applications of Soil Water Balance in Unsaturated Pyroclastic Soils
No full textEvaluation of the monthly soil water balance (SWB) provides a tool for understanding and predicting the effects of seasonal and long-term changes in soil water conditions within many geotechnical problems. In this paper, two applications of the SWB approach in the pyroclastic partially saturated soils are shown. Firstly, rainfall, evapotranspiration, water storage measured or estimated at the experimental site in Monteforte Irpino (in Southern Italy) are shown. Secondly, rainfall, infiltration, actual evapotranspiration and water storage measured by data provided by a physical model are shown. In the both cases, data are reported over two years (2010-2012). The physical model was constituted by a wooden tank filled with reconstituted silty pyroclastic soil taken from experimental site at Monteforte Irpino (AV) and it was exposed to the atmosphere at a site in Napoli.
Comparison between soil hydraulic behaviours observed is discussed and the scale effects on the estimation of the SWB are
analysed, treating with practical implications. From the results, it is clear that similar trends in SWB and the same value of
suction over wet season (10 kPa) can be observed at both the scales in spite of differences in meteorological conditions and hydraulic properties of soils exposed to atmosphere
Assessing the potential effects of Climate Changes on landslide phenomena affecting pyroclastic covers in Nocera area (Southern Italy)
No full textThe effects of Climate Changes (CC) on natural hazardsinduced byweather forcing representan issue which has beenwidely debated inthe last years. Climate projections allowed to detect clear indications about the future trend of the main atmospheric forcing although affected by significant uncertainties concerning the magnitude. However, the crucial role played by the specific geomorphological contexts makes much more challenging understanding how such variations could affect occurrence and magnitude of landslide hazards. These factors help understanding because it is often unreliable carrying out assessments on large areas but is often necessary trying to evaluate the potential effects of CC on geo-hydrological hazards at slope scale. The main aim of this paper is the definition of a framework for the evaluation of potential variations of occurrences of landslide events affecting slopes of NoceraInferiore (Southern Italy) under the effect of CC. Such slopeshave been affected in recent years, inseveral occasions, by flowslide phenomena inducing large economic lossesand fatalities. The framework, consisting of two macro components, is tested to check its predictive capability of landslide behavior. It is then applied to provide a prediction of "potential" events for near and long time horizon scenarios. The study highlightspotential variations (increases) in triggering frequency under the effect of different concentration scenarios and time horizons
Letter from Geraldine Ferraro to Italian Author, Alfredo Ferraro
No full textLetter from Geraldine Ferraro to Italian author, Alfredo Ferraro. Geraldine Ferraro thanks him for sending a copy of his book.https://ir.lawnet.fordham.edu/vice_presidential_campaign_correspondence_1984_international/1166/thumbnail.jp
Experiments to investigate the hydrological behaviour of volcanic covers
No full textThe work investigates experimentally the hydrological response of a volcanic silty-sand involved in the Nocera Inferiore flowslide occurred in 2005. To this aim, an infiltration column and a lisimeter have been developed. In both, the same volcanic silty-sand soil has been placed through the pluvial deposition technique. The former device has been used to carry out infiltration laboratory tests aimed at investigating hydraulic boundary conditions acting at the lowermost surface of the soil column for different contact types (pumices, atmosphere, a geosynthetic material). The latter exposes the layer at atmosphere to investigate water fluxes across the uppermost surface induced by the soil-atmosphere interaction. The work shows how the developed physical models feature the hydrological behavior of a silty pyroclastic layer under various meteorological forcing, allowing to build up frameworks useful to characterize the main factors inducing landslides
Physically based approaches incorporating evaporation for early warning predictions of rainfall-induced landslides
No full textIn the field of rainfall-induced landslides on sloping covers, models for early warning predictions require an adequate trade-off between two aspects: prediction accuracy and timeliness. When a cover's initial hydrological state is a determining factor in triggering landslides, taking evaporative losses into account (or not) could significantly affect both aspects. This study evaluates the performance of three physically based predictive models, converting precipitation and evaporative fluxes into hydrological variables useful in assessing slope safety conditions. Two of the models incorporate evaporation, with one representing evaporation as both a boundary and internal phenomenon, and the other only a boundary phenomenon. The third model totally disregards evaporation. Model performances are assessed by analysing a well-documented case study involving a 2 m thick sloping volcanic cover. The large amount of monitoring data collected for the soil involved in the case study, reconstituted in a suitably equipped lysimeter, makes it possible to propose procedures for calibrating and validating the parameters of the models. All predictions indicate a hydrological singularity at the landslide time (alarm). A comparison of the models' predictions also indicates that the greater the complexity and completeness of the model, the lower the number of predicted hydrological singularities when no landslides occur (false alarms)
Calibration of TDRs and heat dissipation probes in pyroclastic soils
No full textIn situ monitoring of the hydrological response probably represents the most effective approach for implementing early warning systems for landslides in pyroclastic covers. To this aim, the chosen devices have to be both reliable and robust, requiring minimal efforts for their maintenance.
Among others, two sensors meet such requirements: TDR and heat dissipation probes, used to measure, respectively, volumetric water content and matric suction.
Their utilization on large scale is however partially affected by requiring articulated calibration procedures. They have to be provided for each soil type in TDRs and for each probe in dissipation probes.
In this paper, for both measurement techniques, the advantages and disadvantages of their use, the procedures developed for their calibration, the evolutions obtained in the subsequent three years of validation of calibration relationships are discussed. Finally, the comparison of the obtained results with those available in the literature for in situ monitoring systems is shown. are shown for in situ monitoring systems. (C) 2014 Elsevier B.V
Processi di infiltrazione ed evaporazione nei terreni piroclastici illustrati attraverso la selezione di alcuni eventi rappresentativi
No full textRainfall and potential evaporation represent maximum water fluxes across the ground surface. Actual fluxes instead depend also on crop characteristics and the state of the topsoil (water content and suction). To understand and characterize mechanisms that regulate the soil atmosphere interaction in pyroclastic soils a physical model has been arranged. It consists in a tank containing 1 m3 of pyroclastic soil exposed at elements and suitably instrumented to measure those variables describing atmosphere and soil states. The monitoring activity carried out over more than two years provides several meteorological events, either representative or singular, occurring during wet and dry periods. This activity also provides the wide experimental dataset needed to understand how the soil state affects seepage mechanisms associated with and regulating actual evaporation and infiltration
Prediction of suction evolution of silty pyroclastic covers in flume tests and field monitoring
No full textThe paper shows the results of calibration, validation and blind prediction of two different test cases: the former is a flume test for experiment involving a homogenous soil; the latter is a field case for the layered natural soil coming from Cervinara site. The results have been carried out through hydraulic and mechanical simplified approac
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