An experimental study of the behaviour of two rockfills accounting for the effects of degree of saturation

Rockfill dams have become more and more recognized for their safety, economy and adaptability to widely varying site conditions. As a contribution to the understanding of the main factors affecting the rockfill behaviour, the paper reports and discusses experimental data on several aspects relevant to the interpretation and analysis of their in-situ response. The experimental programme involved three series of oedometric tests on specimens of two different gravels having the same grading, reconstituted at the same initial relative density. Experimental observations on rockfills compressibility are presented and discussed: attention is paid to the role of degree of saturation (Sr) through the analysis of "driest", "fully saturated"conditions, and the transition from one to the other. Grain crushing tests on dry and saturated soil particles are also reported. Grain size distributions of the specimens, both after compaction and after the oedometer tests, are compared in the paper. The results show that the effect of Sr cannot be overlooked in the mechanical characterization of the material, especially in rockfill/stress conditions prone to crushin

Ccella triassiale con controllo dell’umidità relativa

Il comportamento meccanico dei rockfill dipende dal livello tensionale e dalla densità relativa, ma anche dalla rottura delle particelle, fenomeno caratteristico dei terreni a grana grossa. Come ampiamente riconosciuto in letteratura, la rottura dei grani è influenzata dalla composizione mineralogica, dall’assortimento granulometrico ed anche dall'umidità relativa (RH). Recentemente, presso il Laboratorio di Geotecnica del Dipartimento di Ingegneria Civile, Edile ed Ambientale dell’Università degli Studi di Napoli “Federico II”, è stata avviata una ricerca finalizzata proprio allo studio sperimentale del comportamento meccanico di rockfill in condizioni di parziale saturazione. Lo studio si avvale dell’impiego di una cella triassiale di grandi dimensioni modificata per imporre nel provino anche condizioni di parziale saturazione: il controllo dell’umidità relativa, e quindi della suzione totale, consiste nell’imporre il trasferimento di vapore acqueo mediante un sistema di convezione forzata, ed avviene per mezzo di soluzioni saline collocate all’interno di un recipiente esterno. La cella è stata anche modificata introducendo, per la misura delle deformazioni assiali e radiali, un sistema magnetico innovativo di rilevamento forma/volume denominato Magnetic Shape Detector (MSD), attualmente in fase di messa a punto

Integrated stratigraphic reconstruction for the last 80 kyr in a deep sector of the Sardinia Channel (Western Mediterranean)

A quantitative analysis of planktonic foraminifera, coupled with petrophysical and paleomagnetic measurements and 14C AMS calibrations, was carried out on a deep core recovered in the Sardinia Channel (Western Mediterranean Sea), during the CIESM Sub2 survey, providing an integrated stratigraphic time-framework over the last 80 kyr. Significant changes in the quantitative distribution of planktonic foraminifera allowed the identification of several eco-bioevents useful to accurately mark the boundaries of the eco-biozones widely recognised in the Western Mediterranean records and used for large scale correlations. Namely, 10 eco-biozones were identified based on the relative abundance of selected climate sensitive planktonic foraminiferal species. Sixteen codified eco-bioevents were correlated with the Alboran Sea planktonic foraminiferal data and four climatic global events (Sapropel S1, Younger Dryas, Greenland Isotope Interstadial 1, Greenland Isotope Stadial 2, Heinrich event H1-H6) were recognized. The eco-bioevents together with the 14C AMS calibrations allowed us to define an accurate age model, spanning between 2 and 83 kyr. The reliability of the age model was confirmed by comparing the colour reflectance (550 nm%) data of the studied record with the astronomically tuned record from the Ionian sea (ODP-Site 964). A mean sedimentation rate of about 7 cm/kyr included three turbidite event beds that were chronologically constrained within the relative low stand and lowering sea level phases of the MIS 4 and 3. The deep-sea sedimentary record includes a distinct tephra occurring at the base of the core which dates 78 ka cal. BP. The paleomagnetic data provide a well-defined record of the characteristic remanent magnetization that may be used to reconstruct the geomagnetic paleosecular variation for the Mediterranean back to 83 kyr

Integrated stratigraphic reconstruction for the last 80 kyr in a deep sector of the Sardinia Channel (Western Mediterranean)

A quantitative analysis of planktonic foraminifera, coupled with petrophysical and paleomagnetic measurements and 14C AMS calibrations, was carried out on a deep core recovered in the Sardinia Channel (Western Mediterranean Sea), during the CIESM Sub2 survey, providing an integrated stratigraphic time-framework over the last 80 kyr. Significant changes in the quantitative distribution of planktonic foraminifera allowed the identification of several eco-bioevents useful to accurately mark the boundaries of the eco-biozones widely recognised in the Western Mediterranean records and used for large scale correlations. Namely, 10 eco-biozones were identified based on the relative abundance of selected climate sensitive planktonic foraminiferal species. Sixteen codified eco-bioevents were correlated with the Alboran Sea planktonic foraminiferal data and four climatic global events (Sapropel S1, Younger Dryas, Greenland Isotope Interstadial 1, Greenland Isotope Stadial 2, Heinrich event H1-H6) were recognized. The eco-bioevents together with the 14C AMS calibrations concurred to define an accurate age model, spanning between 2 and 83 kyr cal. BP. The reliability of the age model was confirmed by comparing the colour reflectance (550 nm%) data of the studied record with the astronomically tuned one of the Ionian sea (ODP-Site 964). A mean sedimentation rate of about 7 cm/kyr was evaluated including three turbidite event beds that were chronologically constrained within the relative low stand and lowering sea level phases of the MIS 4 and MIS 3. The deep sea sedimentary record includes a distinct tephra occurring at the base of the core which dates 79 ka. The paleomagnetic data provide a well-defined record of the characteristic remanent magnetization that may be used to reconstruct the geomagnetic paleosecular variation for the Mediterranean back to 83 kyr cal. BP

Stratigrafia ed assetto geometrico dell’Unità del Sannio nel settore settentrionale dei monti del Matese

New stratigraphic and biostratigraphic data arising from the realization of the Sheet No. 405 "Campobasso" of the new Geological map of Italy (1:50.000 scale - CARG Project) allowed, for the first time in this area, to stratigraphically and cartographically define all the ranges composing the basinal Sannio Unit Auct.. Structural analysis and the chronostratigraphic redefinition of siliciclastic deposits covering the Sannio Unit and the carbonate platform successions of the Matese- Frosolone Units, indicate two main evolutionary stages in the Miocene- Pliocene structuring of this portion of the Southern Apennines. In the first stage, starting before Serravallian times, E-verging contraction affected exclusively the basinal units together with their siliciclastic cover. During the second stage, beginning after early Messinian times, NE-verging compression involved both the basinal Sannio Unit and the Matese-Frosolone Units.UnpublishedISPRA - Roma, Italy2.2. Laboratorio di paleomagnetismorestricte

Integrated stratigraphy for the Late Quaternary in the eastern Tyrrhenian Sea

A high-resolution integrated stratigraphy is presented for the Late Quaternary in the southern-eastern Tyrrhenian Sea. It is based on calcareous plankton taxa (planktonic foraminifera and nannoplankton) distribution, d18OGlobigerinoides ruber record, tephrostratigraphy and radiometric dating methods (210Pb and 137Cs, AMS 14C) for a composite sediment core (from the top to the bottom, C90-1m, C90 and C836) from the continental shelf of the Salerno Gulf. High sedimentation rates from ca 1 cm/100 y for the early Holocene, to 3.45 cm/100 y for the middle Holocene to 8.78 cm/100 y from late Holocene and to 20 cm/100 y for the last 600 AD, make this area an ideal marine archive of secular paleoclimate changes. Quantitative distributional trend in planktonic foraminifera identify seven known (1Fe7F) eco-biozones, and several auxiliary bioevents of high potential for Mediterranean biostratigraphic correlation. Recognised were: the acme distribution of Neogloboquadrina pachyderma r.c. between 10.800 0.400 ka BP and 5.500 0.347 ka BP, a strong increase in abundance of Globorotalia truncatulinoides r.c. and l.c. at 5.500 0.347 ka BP and at 4.571 0.96 ka BP, respectively, an acme interval of Globigerinoides quadrilobatus (between 3.702 0.048 ka BP and 2.70 0.048 ka BP) and the acme/paracme intervals of T. quinqueloba (acme between 3.350 0.054 ka BP and 1.492 0.016 ka BP; paracme between 1.492 0.016 ka BP and 0.657 0.025 ka BP; acme beginning 0.657 0.025 ka BP). These results, integrated with trends of selected calcareous nannofossil species (Florisphaera profunda, Brarudosphaera bigelowii, Gephyrocapsa oceanica and Emiliania huxleyi) and d18OG. ruber signature, are consistent with the most important pre-Holocene and early Holocene paleoclimatic and paleoceanographic phases i.e., the BöllingeAllerod, the Younger Dryas and the time interval of Sapropel S1 deposition in the eastern Mediterranean Sea. These features revealed the high potential of this shallow water environment for high-resolution stratigraphy and correlation for the western Mediterranean. In addition, the chemical characterization of seven tephra layers supplied further data about the age and the dispersal area of some well-known Campi Flegrei explosive events, inferring the possible occurrence of explosive activity at Vesuvius around the middle of the 6th century, and contributing to refine the tephrostratigraphic framework for the last 15 ka in the south-eastern Tyrrhenian Sea.Published71-852.2. Laboratorio di paleomagnetismoJCR Journalrestricte

The impact of the Little ice age on coccolithophores in the central Mediterranea Sea

The Little ice age (LIA) is the last episode of a series of Holocene climatic anomalies. There is still little knowledge on the response of the marine environment to the pronounced cooling of the LIA and to the transition towards the 20th century global warming. Here we present decadal-scale coccolithophore data from four short cores recovered from the central Mediterranean Sea (northern Sicily Channel and Tyrrhenian Sea), which on the basis of ²¹⁰Pb activity span the last 200-350 years. The lowermost part of the record of one of the cores from the Sicily Channel, Station 407, which extends down to 1650 AD, is characterized by drastic changes in productivity. Specifically, below 1850 AD, the decrease in abundance of F. profunda and the increase of placoliths, suggest increased productivity. The chronology of this change is related to the main phase of the Little Ice Age, which might have impacted the hydrography of the southern coast of Sicily and promoted vertical mixing in the water column. The comparison with climatic forcings points out the importance of stronger and prolonged northerly winds, together with decreased solar irradiance

Eastern Mediterranean water outflow during the Younger Dryas was twice that of the present day

Eastern Mediterranean deep-intermediate convection was highly sensitive to varying inputs of fresh water fluxes associated with increased rainfall during the African Humid period (15-6 kyr Before Present). Here we investigate changes in the water-outflow from the Eastern Mediterranean Sea since the last deglaciation using neodymium isotope ratios. Our results indicate enhanced outflow during the Younger Dryas, two times higher than present-day outflow and about three times higher than during the last Sapropel. We propose that the increased outflow into the western Mediterranean over the Younger Dryas was the result of the combined effect of 1) enhanced climate-driven convection in the Aegean Sea and 2) reduced convection of western deep water during this period. Our results provide solid evidence for an enhanced Younger Dryas westward flow of Eastern Mediterranean sourced waters in consonance with an intensification of Mediterranean water-outflow during a weakened state of the Atlantic circulatio