Laboratory Investigation on the Effects of Overconsolidation and Saturation on Undrained Monotonic Shear Behavior of Granular Material     

Noureddine Della  Ahmed Arab  Mostefa Belkhatir 《Marine Georesources & Geotechnology》2013,31(3):218-229

In order to study pore water response and static liquefaction characteristics of silty sand, which has previously experienced liquefaction, two series of monotonic triaxial tests were run on medium dense sand specimens (RD = 50%) at confining pressure of 100 kPa. In the first test series, the influence of the soil saturation under undrained static loading has been studied. It summarizes results of monotonic tests performed on Chlef sand at various values of the Skempton's pore pressure coefficient. Analysis of experimental results gives valuable insights on the effect of soil saturation on sand response to undrained monotonic paths. In the second series of tests, the overconsolidation influence on the resistance to the sands liquefaction has been realized on samples at various values of overconsolidation ratios (OCR). It was found that the increase of overconsolidation ratio (OCR) increases the resistance of sands to liquefaction.  相似文献   

Effects of limestone petrography and calcite microstructure on OPC clinker raw meals burnability     

Galimberti  Matteo  Marinoni  Nicoletta  Della Porta  Giovanna  Marchi  Maurizio  Dapiaggi  Monica 《Mineralogy and Petrology》2017,111(5):793-806

Mineralogy and Petrology - Limestone represents the main raw material for ordinary Portland cement clinker production. In this study eight natural limestones from different geological environments...  相似文献   

Experimental Study of Undrained Shear Strength of Silty Sand: Effect of Fines and Gradation   总被引：2，自引：1，他引：1  

Mostefa Belkhatir  Ahmed Arab  Noureddine Della  Tom Schanz 《Geotechnical and Geological Engineering》2012,30(5):1103-1118

Two strong earthquakes occurred in the region of Chlef (north western part of Algeria) during the last century. From the geological context, there were several great masses of sandy soil ejections on to the ground surface level and severe damages to civil and hydraulic structures. These damages were due to the soil liquefaction phenomenon. The objective of this laboratory investigation is to study the effect of low plastic fines and gradation characteristics on the undrained shear strength (liquefaction resistance) response of sand-silt mixture samples. For this purpose, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated silty sand samples with different fines content ranging from 0 to 50?% at two initial relative densities (D_r?=?20 and 91?%). The initial confining pressure was kept at 100?kPa. The evaluation of the data indicates that the undrained shear strength at the peak (q_peak) can be correlated to the undrained residual strength (S_us), the excess pore pressure (Δu), the fines content (F_c) and the intergranular void ratio (e_s). The test results indicate also that the undrained shear strength at the peak decreases with the increment of the coefficient of uniformity and fines content as well as with the decrement of the mean grain size in the range of 0–50?% fines content for both relative densities (D_r?=?20 and 91?%).  相似文献   

The thermal stability of sideronatrite and its decomposition products in the system Na2O–Fe2O3–SO2–H2O     

Gennaro Ventruti  Fernando Scordari  Giancarlo Della Ventura  Fabio Bellatreccia  Alessandro F. Gualtieri  Andrea Lausi 《Physics and Chemistry of Minerals》2013,40(8):659-670

The thermal stability of sideronatrite, ideally Na₂Fe³⁺(SO₄)₂(OH)·3(H₂O), and its decomposition products were investigated by combining thermogravimetric and differential thermal analysis, in situ high-temperature X-ray powder diffraction (HT-XRPD) and Fourier transform infrared spectroscopy (HT-FTIR). The data show that for increasing temperature there are four main dehydration/transformation steps in sideronatrite: (a) between 30 and 40 °C sideronatrite transforms into metasideronatrite after the loss of two water molecules; both XRD and FTIR suggest that this transformation occurs via minor adjustments in the building block. (b) between 120 and 300 °C metasideronatrite transforms into metasideronatrite II, a still poorly characterized phase with possible orthorhombic symmetry, consequently to the loss of an additional water molecule; X-ray diffraction data suggest that metasideronatrite disappears from the assemblage above 175 °C. (c) between 315 and 415 °C metasideronatrite II transforms into the anhydrous Na₃Fe(SO₄)₃ compound. This step occurs via the loss of hydroxyl groups that involves the breakdown of the [Fe³⁺(SO₄)₂(OH)] _∞ ^2? chains and the formation of an intermediate transient amorphous phase precursor of Na₃Fe(SO₄)₃. (d) for T > 500 °C, the Na₃Fe(SO₄)₃ compound is replaced by the Na-sulfate thenardite, Na₂SO₄, plus Fe-oxides, according to the Na₃Fe³⁺(SO₄)₃ → 3/2 Na₂(SO₄) + 1/2 Fe₂O₃ + SO_x reaction products. The Na–Fe sulfate disappears around 540 °C. For higher temperatures, the Na-sulfates decomposes and only hematite survives in the final product. The understanding of the thermal behavior of minerals such as sideronatrite and related sulfates is important both from an environmental point of view, due to the presence of these phases in evaporitic deposits, soils and sediments including extraterrestrial occurrences, and from the technological point of view, due to the use of these materials in many industrial applications.  相似文献   

Bacterial response to seasonal changes in labile organic matter composition on the continental shelf and bathyal sediments of the Cretan Sea     

Roberto Danovaro  Daniela Marrale  Antonio Dell'Anno  Norberto Della Croce  Anastasios Tselepides  Mauro Fabiano 《Progress in Oceanography》2000,46(2-4)

Bacterial abundance, biomass and cell size were studied in the oligotrophic sediments of the Cretan Sea (Eastern Mediterranean), in order to investigate their response to the seasonal varying organic matter (OM) inputs. Sediment samples were collected on a seasonal basis along a transect of seven stations (ranging from 40 to 1570 m depth) using a multiple-corer. Bacterial parameters were related to changes in chloroplastic pigment equivalents (CPE), the biochemical composition (proteins, lipids, carbohydrates) of the sedimentary organic matter and the OM flux measured at a fixed station over the deep basin (1570 m depth). The sediments of the Cretan Sea represent a nutrient depleted ecosystem characterised by a poor quality organic matter. All sedimentary organic compounds were found to vary seasonally, and changes were more evident on the continental shelf than in deeper sediments. Bacterial abundance and biomass in the sediments of the Cretan Sea (ranging from 1.02 to 4.59 × 10⁸ cells g⁻¹ equivalent to 8.7 and 38.7 μgC g⁻¹) were quite high and their distribution appeared to be closely related to the input of fresh organic material. Bacterial abundance and biomass were sensitive to changes in nutrient availability, which also controls the average cell size and the frequency of dividing cells. Bacterial abundance increased up to 3-fold between August '94 and February '95 in response to the increased amount of sedimentary proteins and CPE, indicating that benthic bacteria were constrained more by changes in quality rather than the quantity of the sedimentary organic material. Bacterial responses to the food inputs were clearly detectable down to 10 cm depth. The distribution of labile organic compounds in the sediments appeared to influence the vertical patterns of bacterial abundance and biomass. Cell size decreased significantly with water depth. Bacterial abundance and biomass were characterised by clear seasonal changes in response to seasonal OM pulses. The strong coupling between protein flux and bacterial biomass together with the strong bacterial dominance over the total biomass suggest that the major part of the carbon flow was channelled through the bacteria and the benthic microbial loop.  相似文献   

Use of genetic algorithm in new approach to modeling of flood routing     

El Alaoui El Fels  Abdelhafid  Alaa  Noureddine  Bachnou  Ali 《中国海洋湖沼学报》2019,37(1):72-78

Journal of Oceanology and Limnology - The hydrological models and simplified methods of Saint-venant equations are used extensively in hydrological modeling, in particular for the simulation of the...  相似文献   

Meiofauna of the deep Eastern Mediterranean Sea: distribution and abundance in relation to bacterial biomass, organic matter composition and other environmental factors     

Roberto Danovaro  Norberto Della Croce  Anastasios Eleftheriou  Mauro Fabiano  Nadia Papadopoulou  Chris Smith  Anastasios Tselepides 《Progress in Oceanography》1995,36(4)

Quantitative information on the abundance and biomass of metazoan meiofauna was obtained from samples collected at 15 deep-sea stations in the Eastern Mediterranean Sea (533–2400m). Meiofaunal abundance was compared to bacterial biomass and other environmental factors such as the total sedimentary organic matter content, the concentrations of the main biochemical classes of organic compounds (i.e. proteins, carbohydrates and lipids) and to ATP. To estimate the sedimentation potential of primary organic matter, sediment bound chloroplastic pigment equivalents (CPE) were assayed. Meiofaunal density was very low ranging from 4 ind.10cm⁻² (Station A4, 1658m depth) to 290 ind.10cm⁻² (Station A12, 636m depth). Nematodes were the numerically dominant taxon (68% of total meiofauna) and were usually confined to the top 6cm of the sediments. Total meiofaunal biomass ranged from 2.78μgC 10cm⁻² (Station A4) to 598.34μgC 10cm⁻² (Station 15A). There was a significant decrease in the density of metazoan meiofauna with water depth. Bacterial biomass largely dominated the total biomass (as the sum of bacterial and meiofaunal biomass) with an average of 73.2% and accounted for 35.8% of the living biomass (as ATP carbon) whereas meiofaunal biomass accounted only for 6.56%. Bacterial biomass was significantly related to the DNA concentrations of the sediment. A significant correlation between ATP concentration and CPE content was also found. No correlations were found between meiofauna, ATP and CPE, or between meiofauna and bacterial parameters. The significant relationship between meiofaunal density and the ratio of labile organic matter/total organic matter indicates that deep-sea meiofauna inhabiting an extremely oligotrophic environment (such as the Eastern Mediterranean) may be more nutritionally dependent upon the quality than on the quantity of sedimentary organic matter.  相似文献   

Five supernova survey galaxies in the southern hemisphere. I. Optical and near-infrared database     

A. A. Hakobyan  A. R. Petrosian  G. A. Mamon  B. McLean  D. Kunth  M. Turatto  E. Cappelaro  F. Mannucci  R. J. Allen  N. Panagia  M. Della Valle 《Astrophysics》2009,52(1):40-53

The determination of the supernova (SN) rate is based not only on the number of detected events, but also on the properties of the parent galaxy population. This is the first paper of a series aimed at obtaining new, refined, SN rates from a set of five SN surveys, by making use of a joint analysis of near-infrared (NIR) data. We describe the properties of the 3838 galaxies that were monitored for SNe events, including newly determined morphologies and their DENIS, and POSS-II/UKST I, 2MASS and DENIS J and K_s and 2MASS H magnitudes. We have compared 2MASS, DENIS and POSS-II/UKST IJK magnitudes in order to find possible systematic photometric shifts in the measurements. The DENIS and POSS-II/UKST I band magnitudes show large discrepancies (mean absolute difference of 0.4 mag.), mostly due to different spectral responses of the two instruments, with an important contribution (0.33 mag rms) from the large uncertainties in the photometric calibration of the POSS-II and UKST photographic plates. In the other wavebands, the limiting near infrared magnitude, morphology, and inclination of the galaxies are the most influential factors which affect the determination of photometry of the galaxies. Nevertheless, no significant systematic differences have been found between any pair of NIR magnitude measurements, except for a few percent of galaxies showing large discrepancies. This allows us to combine DENIS and 2MASS data for the J and K_s filters. Published in Astrofizika, Vol. 52, No. 1, pp. 47–62 (Februay 2009).  相似文献   

On the evolution of the cosmic supernova rates     

Piero Madau  Massimo Della Valle  & Nino Panagia 《Monthly notices of the Royal Astronomical Society》1998,297(1):L17-L22

The Galactic radio-emitting X-ray binary Cygnus X-3 is known to be a source of large-scale radio jets associated with periods of intense radio flaring. These jets have been found to have an expansion velocity of ∼0.3 c and are believed (on kinematic grounds) to lie close to the plane of the sky. We present new observations of Cygnus X-3 using the VLBA at 15 GHz. These observations, which included the detection of two small flares, show an additional kind of behaviour with apparent superluminal expansion along both major and minor axes. Evidence for superluminal activity has been found in a number of X-ray binary systems such as GRS 1915+105 and GRO J1655−40 with their superluminal radio jets. Apparently similar morphologies of the Galactic and extragalactic jet sources have led to the X-ray binaries being described as 'micro-quasars'. The superluminal expansion seen in our results appears to be different in nature from these other two sources, and a number of mechanisms are presented and discussed.  相似文献   

Effect of XFe and fO2 on the FTIR and Mössbauer spectra of richterites in the system K2O-Na2O-CaO-MgO-FeO-Fe2O3-TiO2-SiO2-H2O     

J. Sergent  J. -L. Robert  B. Boukili  G. Della Ventura 《Physics and Chemistry of Minerals》1996,23(4-5):308-308

  相似文献