1,721,017 research outputs found
Analysis of the slope-vegetation-atmosphere interaction for the design of the mitigation measures of landslide risk in clayey slopes
No full textL’attività di ricerca affrontata dal dottorando riguarda l'evoluzione delle condizioni di equilibrio nel tempo in riferimento alla stabilità di frane clima-indotte. L'approccio seguito è principalmente legato al confronto tra analisi numeriche e dati di monitoraggio di campo, che sono di fondamentale importanza per poter determinare la veridicità delle previsioni numeriche.
La ricerca mira innanzitutto ad identificare i principali fattori interni ed esterni da considerare per il replicare correttamente numericamente, le evidenze sul campo. Come tale in questa fase del lavoro, lo scopo è quello di diagnosticare l'attuale attività stagionale osservata ricorrentemente e documentata in un caso di studio (la frana di Pisciolo) tramite monitoraggi di sito. Attraverso strategie numeriche diverse e gradualmente più complesse si è effettuato un calcolo del processo franoso. In particolare, sono state condotte analisi numeriche idrauliche e idromeccaniche, volte a mettere in luce i punti di forza e di debolezza di ciascuna strategia numerica nella modellazione dell’attività attuale della frana in studio.
La rappresentatività del pendio di Pisciolo con riferimento a diversi meccanismi di frana nell'Appennino sud-orientale, rende questo caso di particolare interesse, poiché le conclusioni sito-specifiche sono valide anche per casi di studio meno studiati, o meno monitorati.
Questa circostanza è molto rilevante, dal momento che consente una trasposizione di concetti e strategie di progettazione dal caso specifico (la frana di Pisciolo) ad altri casi di studio, anche senza studi dettagliati sito-specifici.
L'obiettivo finale di questo lavoro di ricerca è di fornire consigli per quanto concerne due diverse strategie di mitigazione; in particolar modo il dottorando si è occupato della progettazione di sistemi di allerta e di interventi di bioingegneria in relazione al meccanismo di frana di riferimento.
Il sistema di allerta è progettato con riferimento a diversi corpi di frana, da superficiale a profondo, evidenziando le differenze sia per quanto riguarda le variabili di soglia di riferimento sia che i valori di soglia. Questa analisi viene effettuata me-diante modellazione numerica idraulica seguita dal calcolo del fattore di sicurezza con il metodo del limite di equilibrio.
L'input forzante climatico per queste analisi è ottenuto da dati climatici reali, dal 2001 al 2016, per i quali sono disponibili precipitazioni e temperature minime e massime da annali climatici forniti da una stazione di monitoraggio climatico vicina al versante di Pisciolo. I risultati della diagnosi del meccanismo di frana consentono di comprendere che anche la condizione climatica preesistente può influire sul successivo risultato di un certo input climatico. Di conseguenza tra tutti gli anni monitorati disponibili, sono stati scelti due anni diversi come rappresentativi di uno molto piovoso e di uno molto secco; questi sono stati applicati prima dell'applicazione dell'anno climatico in esame.
L'analisi dell'efficienza di un intervento di ingegneria naturalistica o di bioingegneria è stata anch’essa analizzata in questa attività di ricerca; in particolare, è stato effettuato uno studio preliminare sull'uso di colture radicate sul suolo per la stabilizzazione di corpi superficiali e profondi.
A questo scopo, un campo prova (circa 2000 m2) è stato allestito al piede del meccanismo franoso di Pisciolo, allo scopo di determinare l'efficienza idraulica di alcuni piante selezionate. I vari tipi di colture sono stati seminati nell’area del test e il monitoraggio delle variabili climatiche, dello stato di copertura superficiale (zona insatura) e dello stato del suolo più profondo (zona saturata) è iniziato a gennaio 2018 ed è tuttora in corso.
Una piattaforma numerica di equazioni differenziali per risolvere il numerica-mente il calcolo termo-idraulico è stato descritto, con lo scopo futuro di calcolare in maniera inversa i flussi verso l’atmosfera evaporativi e traspirativi indotti dalle piante.
Pur non essendo conclusivo, questo studio può essere scientificamente rilevante, ed è quindi auspicabile che esso abbia ripercussioni sul lato pratico, risultando utile per future linee guida per la progettazione di interventi di bioingegneria simili a quello in studio.The present research activity deals with the evolution of the equilibrium conditions in time with reference to climate-induced landslides. The approach followed herein is mainly linked to the comparison between numerical analyses and field monitoring data which are of major importance to state the success of the numerical predictions.
The research is first aimed at identifying the main internal and external factors to be accounted for numerically replicating the field evidence. As such in this step of the work, the purpose is to diagnose the current seasonal activity observed in a case study (the Pisciolo slope) in terms of hydraulic and mechanical behavior. In particular, a boundary value problem has been numerically solved with different and gradually more complex numerical strategies. Specifically, hydraulic and hydro-mechanical numerical analyses have been carried out, aimed at highlighting the strengths and weaknesses of each numerical strategy in modeling the current activity of the Pisciolo slope.
The representativeness of the Pisciolo slope with respect to several landslide mechanisms in the South-Eastern Apennine, makes this case study of particular interest, since the site-specific conclusions drawn may be also valid for other mechanisms.
This circumstance appears to be very relevant, since it allows for transposition of concepts and design strategies from a representative slope to others, even without very detailed site-specific studies.
The final aim of this research work is to give advice on two different mitigation measures, addressing the design of early warning systems and bio-engineering interventions for the landslide mechanism of reference.
The early warning system is designed with reference to different landslide bodies, from shallow to deep, highlighting the differences on both the reference threshold variables and threshold values. This analysis is carried out by means of hydraulic numerical modeling followed by the computation of the safety factor with the limit equilibrium method.
The climatic forcing input for these analyses is obtained from real climatic data, from 2001 to 2016, for which rainfall and minimum and maximum temperatures were available from climatic annals provided by a climatic monitoring station close the Pisciolo slope. The results of the diagnosis of the landslide mechanism allow realizing that also the pre-existent climatic condition may affect the subsequent impact of a certain climatic input. As such, among all the monitored years available, two different years have been chosen as representative of a very rainy and a very dry one; those have been applied prior the application of the climatic year under investigation.
The analysis of the efficiency of a bio-engineering intervention has been of interest in this research activity; in particular, the use of deep-rooted crops on the soil cover for stabilizing shallow and deep bodies is studied herein.
As such, a test site (approx. 2000 m2) has been installed at the toe of the Pisciolo landslide, aimed at determining the hydraulic efficiency of some selected crop types. The various crop types have been seeded into the test site, and the monitoring of climatic variables, the shallow cover state (unsaturated zone), and the deeper soil state (saturated zone) has been activated in January 2018 and is still on-going.
A numerical platform of differential equations for solving the thermo-hydraulic boundary value problem is described, with the future aim to back-calculate the upward fluxes of evaporation and plant-induced transpiration.
Although not being conclusive, this study may be scientifically relevant and is then intended to have repercussions on the practical side, being useful for future guidelines for the design of bio-engineering interventions
Coupled effect of pluviometric regime and soil properties on hydraulic boundary conditions and on slope stability
No full textThe case of a landslide in Southern Italy was studied by modeling pore pressure distribution under steady and transient conditions. The goal was to interpret the in situ piezometric and inclinometric measurements, and to investigate the effects of the pluviometric regime on the slope stability. Steady state analyses show that the hypothesis of zero pore pressure at the ground surface gives the best fit between theoretical and experimental results, despite the nearly arid climate. The results of the transient state analyses show that the condition of zero pore pressure is appropriate for both rainy and non-rainy periods because of the particular soil properties, i.e. heterogeneity, compressibility and hydraulic conductivity. This condition generates a distribution of pore pressures which can justify the observed horizontal displacements
Integrated measurements for aerosol properties detection in a rural site in South-Italy.
No full textRivelazione di BC, BrC e OC mediante etalometro AE31 in siti caratterizzati da differenti emissioni
No full textAerosol characterization in a semi-rural site in South-Italyby combined in-situ and ground-based remote sensingmeasurements
No full textHigh resolution radiometric together with in-situ gravimetric and aethalometer
measurements have been performed in a semi-rural site in Southwest Italy (Tito Scalo,
40° 35’ N, 15° 41’ E, 750m a.s.l) to derive aerosols optical and physical properties. The
measurement site is located in the Mediterranean area and this condition allows to
monitor aerosol properties variation due to the influence of air masses with different
origin. In particular, dust particles from Saharan desert could be present together with
polluted and smoke aerosol mainly from Central and Eastern Europe. Moreover marine
particles are an almost constant component both from the Mediterranean itself and from
the Atlantic Ocean. Some anthropogenic local sources impact the site, such as few little
plants and a main road. Columnar properties have been inferred by a high resolution
(1.5 nm) spectroradiometer Ocean Optics (400nm-800nm) to derive Aerosol Optical
Depths (AODs), Ångström turbidity parameters and size distributions, while daily
mass size distributions at the ground have been obtained by a 13 stages impactor.
Finally, Black Carbon (BC) concentrations have been measured during the campaign
by using an aethalometer and, combining all these measurements, it has been possible to
obtain a closure between aerosol optical and physical properties
Black Carbon and Organic Components in the Atmosphere of Southern Italy: Comparing Emissions from Different Sources and Production Processes of Carbonaceous Particles
Full text linkInitial measurements of black carbon (BC) content at both 880 and 370 nm, obtained in two sites in southern Italy by an aethalometer, have been analyzed. The sites are located in the same region (Basilicata), but are affected by different emission sources. In one case the main source of BC is related to vehicular traffic from a nearby freeway. Data were collected, although not continuously, during 2008, 2009 and 2010. In the second case, a fresh crude-oil pre-treatment plant continuously burns petroleum-derived products, thus contributing to emissions of both carbonaceous matter and its organic component. The corresponding data-set was collected in the period January–April 2011. At the first site, two daily peaks were found for the BC content, typical of vehicles emissions, with maximum values ranging from 2000 ng/m3 to 4700 ng/m3 found during weekdays. This behavior disappears at the weekend or when polluted air-masses from north-east Europe are transported over the measurement site. At the second site, two daily peaks were never found, suggesting that crude oil chemical processes were the main source of the emissions. In this case, the maximum BC values ranged between 1000–8000 ng/m3, depending on the processes occurring at the fresh crude-oil pre-treatment plant. Moreover, the estimated level of BC at 370 nm was higher than that of BC at 880 nm in all months, expect for April, indicating a clear organic component in atmospheric aerosols. Finally, based on a best-fit procedure applied to the seven wavelengths’ absorption coefficients, aerosols with different spectroscopic properties have been detected at these two sites
High resolution measurement of aerosol equivalent scale heigth over wide range
No full textAerosol vertical optical depth (AOD) and horizontal extinction coefficient (AEC) have
been measured with multiwavelength photometers at University of Granada, during the
period 14
th
-18
th
July 2006. The AOD τ
aer
has been measured by using an Avantes
USB2000 high grating spectrometer (440–900 nm, 1.5 nm resolution); at the same
moment a FieldSpec has been used to measure Horizontal Aerosol Extinction
Coefficient (AEC) σ
aer
in the range 400-700 nm , with a resolution of 1 nm. Both AOD
and AEC were used to obtain an equivalent Ae rosol scale height at different wavelength
in the range 440-700 nm , according to Mie scattering theory
Long-term observations of carbonaceous aerosols and related gaseous emissions near a crude-oil plant in South Italy
Full text linkA two-year dataset of almost continuous Black Carbon (BC) content measurements by a Magee AE31 7-wavelenghts aethalometer (370 to 950 nm)near a crude oil pre-treatment plant
in South Italy (Agri Valley, 40.33°N, 15.92° E, 582 m
a.s.l) has been analyzed
Aerosol optical properties in Mediterranean basin underSaharan dust outbreaks
No full textFour measurement campaigns held in three different sites of the Mediterranean
basin and in different years revealed the intrusion of mineral dust coming from North
Africa, as confirmed even by the HYSPLIT back-trajectories analysis. Two of the sites
are located in South Italy, the third one is in South Spain.. One data-set was obtained by
a Monolight spectrometer (400 nm – 800 nm, resolution 3 nm), the other by means of
an Avantes USB2000 spectrometer (400 nm – 900 nm, resolution 1.5 nm). A fitting
procedure and a non-parametric inversion t echnique were applied to the measured
AODs to retrieve, respectively, the Ǻngström parameters α and β and the Aerosol Size
Distributions. Each site is characterised by different size distributions (bi-modal and
Junge functions) but, independently from thes e functions, all the measurements affected
by Saharan dust showed higher particles density in the radii range 0.43 μm ≤ r ≤ 3.0 μm.
The second result is the strong correlation between α and ln( β ) for dust data points
obtained in all sites, suggesting that mineral particles properties predominate over the
background ones. Finally, Aerosol Size Distributions have been simulated, modifying
their log-normal parameters and fixing, time by time, the refractive index values, to
reproduce the experimental α vs. ln( β ) behaviour. In this way, an “equivalent refractive
index” common to the dust data has been retrieved
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