38 research outputs found
Geotechnical characterization of a polluted marine basin
No full textThe work presents the results of an intense experimental research into the chemo-mechanical coupling phenomena involving the sediments from the Mar Piccolo basin (Taranto, South of Italy), severely contaminated by both heavy metals (e.g. Hg, Pb, Cd, Cu and Zn) and organic pollutants (PCBs, PAHs, and dioxins). Among the different matrices involved in the environmental studies, i.e. sediments, water and biota, this research focuses on the submarine sediments and reports the results of both the chemical and the geotechnical investigations carried out during the off-shore campaign, prompted by the Special Commissioner for urgent measures of reclamation, environmental improvement and redevelopment of Taranto.
Geotechnical tests were carried out on more than 50 samples, taken from up to 30 m below the seafloor. The standard equipment and procedures were properly adapted to take into account the influence of salt and organic compounds in the pore fluid. The geotechnical testing programme included tests aiming to characterise physical properties, composition and state of the sediments, oedometer tests to determine the 1D compression and consolidation properties of the soil and CIU triaxial tests for the measurements of both isotropic compressibility and strength. Furthermore, an apparatus was developed for both the squeezing of the sediment and the pore flid extraction of pore fluid during compression. Off-shore piezocone tests were also carried out and the results were used to interpret the stratigraphy and derive engineering properties of soils.
The integration of the geotechnical and chemical data allowed to investigate the effects of the chemo-mechanical interaction processes on the geotechnical behaviour of the sediments, in the light of the most relevant literature.
The Mar Piccolo represents a “natural laboratory” and an emblematic case in the worldwide panorama of polluted sites. Hence, the study offered the possibility to produce and analyse an uncommon coupled database of both geotechnical and chemical results concerning natural geomaterials altered by the presence of different sources of contamination
Geotechnical characterisation of submarine sediments from a polluted site
No full textThe present note discusses some laboratory complexities linked to the geotechnical characterization of the soft polluted sediments sampled down from the Mar Piccolo, i.e. a marine basin located within the urban area of Taranto (south of Italy), for which the environmental remediation has been identified as a national priority. The long-lasting industrial activities, together with the waste collection from the densely populated urban center of Taranto, have been responsible for the severe environmental contamination of the Mar Piccolo. In the field of the remediation and management strategies promoted by the Italian Government, a multidisciplinary investigation has been carried out to achieve the chemical, geological and geotechnical characterization of the sediment in the basin. With this purpose, the standard procedures and equipment for geotechnical testing were properly modified to both minimize the soil disturbance and to take account of the influence of both the pore fluid salinity and the presence of organic compounds, shells, mussels and lapideous elements or industrial waste in the soil
Contaminated marine sites: geotechnical issues bridging the gap between characterisation and remedial strategies
No full textL’articolo presenta un approccio originale alla gestione dei siti marini contaminati in cui l’ingegneria geotecnica fa da cerniera tra la caratterizzazione ambientale e la selezione delle tecnologie di messa in sicurezza. Prendendo ispirazione da un emblematico caso italiano di sistema ambientale ad alta contaminazione, lo studio propone un nuovo approccio basato sul Modello Concettuale di Progetto di Sito (CDSM). Il CDSM include non solo le condizioni al contorno e le informazioni sullo stato corrente del sistema, ma anche i processi in atto al suo interno. Dall’analisi del CDSM sviluppata anche alla luce della Teoria della Complessità, si è potuta costruire una matrice di resilienza utile ad indirizzare la selezione delle opzioni e delle tecnologie per la messa in sicurezza e la bonifica. L’approfondimento sulle caratteristiche chemo-meccaniche dei sedimenti ha, tuttavia, mostrato che il sistema può esistere al bordo, tra caos e complessità, diventando di tipo complesso adattativo e rendendo più difficili le previsioni della sua evoluzione.The article deals with an original approach to contaminated marine sites where geotechnical engineering is bridging the gap between site characterisation and first selection of remedial strategies. The research has been prompted by a highly contaminated marine site in Italy and it is centred on the Conceptual Design Site Model (CDSM). The CDSM is based not only on the knowledge of the main current system’s characteristics and boundary conditions but also on the coupled processes acting within it. The analysis of the model has been developed in light of the Complexity Theory and has brought about the building of the so-called resilience matrix. The matrix is a new tool to address site-specific management options and technology screening. However, the focus on the chemo-mechanical properties of the marine sediments has shown that, at some scale, the whole system can enter the edge-of-chaos. In this condition, the site turns out to be a complex adaptive system and predictions about its future development become more challenging
Caratterizzazione geotecnica di sedimenti fini miscelati con leganti e additivi.
No full textLa nota illustra i risultati preliminari di un’attività sperimentale finalizzata ad indagare gli effetti di trattamenti di stabilizzazione/solidificazione (S/S) sulle caratteristiche chemo-meccaniche di sedimenti marini contaminati, prelevati nel Golfo di Taranto. I sedimenti oggetto di studio contengono elevate concentrazioni di metalli pesanti (Hg, Pb, Cu, Zn) e composti organici (IPA e PCB), anche al di sopra dei limiti di legge. Dato il tenore della contaminazione nei sedimenti, la sperimentazione è stata volta a valutare gli effetti di un trattamento S/S a base di leganti inorganici, quali calce e cemento, aggiunti nella percentuale del 10% in peso, e additivi con funzione adsorbente, quali il carbone attivo (AC) e il biochar (BC), aggiunti nella percentuale del 5% in peso. I dati sperimentali ottenuti dalla caratterizzazione delle proprietà fisiche e meccaniche delle differenti miscele sono stati confrontati con quelli del sedimento non trattato. I risultati mostrano un significativo aumento dei valori del limite plastico con riduzione dell’indice di plasticità e un incremento di compressibilità e resistenza non drenata nei sedimenti trattati, più evidenti nel caso delle miscele con cemento. Di notevole supporto per la progettazione delle azioni di bonifica è l’osservazione che l’aggiunta di additivi (AC, BC) non appare influenzare in modo significativo le proprietà del sedimento trattato. Infatti, tale ricerca si colloca in uno studio più ampio che mira a valutare soluzioni innovative, che rispondano a criteri di efficacia, economicità e sostenibilità ambientale, per la bonifica e il riuso di materiali naturali contaminati
Geo-chemo-mechanical characterization of a polluted marine basin
No full textThe work shows the first results of the characterization of the heavily polluted sediments in the Mar Piccolo basin (Taranto, south of Italy), obtained thanks to an integrated investigation method. In the field of the actions promoted by the Italian Government to select the most sustainable remediation strategies, a multidisciplinary investigation of the site has been carried out involving the reconstruction of the geological set-up of the basin, the analysis of the chemical contamination and the geo-mechanical properties of the sediments collected up to 30 m below the sea floor. The devices and methodologies used for the off-shore sampling, storage and transport of the sediments and for the laboratory testing were specifically designed to obtain the best possible picture of the site. The quality of the soil sampling resulted to be high enough for chemical, geochemical and geotechnical characterization and to develop integrated analyses. With this purpose, the paper discusses preliminary correlations of data, focusing on the geotechnical properties of plasticity that have been interpreted in the light of soil composition and chemical and geological facets of the sediments
Analysis and implications of the miscarriages of justice of Amanda Knox and Raffaele Sollecito
No full textAbstractThe case of the ‘murder of Meredith Kercher’ has been the subject of intense media scrutiny since 2007 when the offence was committed. Three individuals were arrested and accused of the crime. Amanda Knox and Raffaele Sollecito were exonerated in March 2015. Another defendant, Rudy Guede, remains convicted as the sole perpetrator. He was implicated by multiple DNA profiles recovered from the murder room and the bathroom. However, the evidence against Guede contrasted strongly with the limited evidence against two co-defendants, Amanda Knox and Raffaele Sollecito. There were no DNA profiles pertaining to Amanda Knox in the murder room itself. She was separately implicated by a knife recovered remote from the crime scene (discovered in a cutlery drawer at Sollecito’s apartment), along with DNA profiles in a bathroom that she had shared with the victim. Upon analysis a low level trace of DNA attributed to the murder victim was found on the blade of a knife, along with DNA profiles attributed to Amanda Knox from the handle. However, there was no evidence of blood on the knife blade itself. A separate key piece of evidence was a DNA profile attributed to Raffaele Sollecito recovered from a forcibly removed bra-clasp found in the murder room. There followed an extraordinary series of trials and retrials where the pair were convicted, exonerated, re-convicted and finally, in March 2015 they were finally exonerated (no further appeal is possible). Since Knox and Sollecito have been found innocent it is opportune to carry out an extensive review of the case to discover the errors that led to conviction so that similar mistakes do not occur in the future. It is accepted that the DNA profiles attributed to them were transferred by methods unrelated to the crime event itself. There is a wealth of material available from the judgements and other reports which can be analysed in order to show the errors of thinking. The final judgement of the case–the Marasca-Bruno motivation report–exposes the illogicality of much of the previous court proceedings that led to the convictions and provides useful guidance for judges to follow
Marine Sediments from a Contaminated Site: Geotechnical Properties and Chemo-Mechanical Coupling Processes
No full textISSN:2076-326
Subsidence of Artificial Reefs with Bamboo Foundations on a Soft Seabed
No full textThe design of artificial reefs must be based on the criteria of both durability and serviceability. In this respect, the seabed subsidence rate related to the weight of the reefs and of their foundation system should be limited. The horizontal drift of the reefs during their life should be small too. In this study, pertaining to the behavior of artificial reefs made of microsilica concrete and realized with foundations in bamboo near the international airport of Hong Kong, 1-year monitoring data and calculations of reef foundation settlements are shown and discussed to assess the performance of the adopted mixed foundation and to deduce the nature of the long-term subsidence. The subsidence related to the settlements of the foundations was monitored using a Multibeam Echo Sounder System. It was found that the observed subsidence rate cannot be justified by the primary consolidation of the soils forming the seabed. Indeed, secondary consolidation seems to play an important role. Overall, after one year of service, the artificial reefs are considered to be effective in terms of limitation of both subsidence and drift
Effects of bio-chemo-mechanical processes on the properties of contaminated marine sediments
No full textISSN:0016-8505ISSN:1751-7656ISSN:1751-765
Micro to macro behaviour of contaminated marine sediments: experimental evidence of bio-chemo-mechanical processes
No full textThe research deals with a multiscale investigation carried out on contaminated marine sediments from a natural deposit to assess the effects of bio-chemo-mechanical coupled processes which may act in complex natural environments and affect the geotechnical properties of the clays. The research has been triggered by the emblematic case of the contaminated Mar Piccolo (MP) basin in Taranto (Southern Italy), where the high degree of pollution recorded in the clayey sediments at the sea bottom, has been found to worsen water quality and promote bioaccumulation of pollutants in several species. Several samples of sediments from the top layer exhibited peculiar geotechnical properties, in terms of plasticity and activity indexes, compressibility and hydraulic permeability. While the prime suspect for such unconventional behaviour was the chemo-mechanical coupling between soil skeleton and contaminants, an original laboratory analysis carried out on some selected sediments samples showed that the biogeochemical degradation of organic matter and the presence of microfossils and diatoms significantly affect the micro to macro behaviour of polluted marine sediments
