Undrained Strength of Deposited Mine Tailings Beds: Effect of Water Content, Effective Stress and Time of Consolidation   总被引：1，自引：0，他引：1  

Rozalina S. Dimitrova  Ernest K. Yanful 《Geotechnical and Geological Engineering》2011,29(5):935-951

An understanding of the geotechnical behaviour of mine tailings is imperative when evaluating the stability and erosional resistance of sedimented tailings beds; as well as for the design and long-term management of tailings disposal facilities. Laboratory testing was conducted on mine tailings beds of various ages and thicknesses, deposited from concentrated slurries. Measured index properties allowed classifying the tailings as a coarse grained and non-cohesive material. The results obtained from the performed sedimentation experiments showed that the primary consolidation of the tailings beds was complete in approximately 1 h and negligible volume changes occurred in the beds during secondary compression. The undrained shear strength of the tailings beds was measured using an automated fall cone device at a depth interval of 1 cm and a profile of the shear strength variation with depth was obtained. At each tested surface, moisture content specimens were taken to determine the moisture content profile of the tested tailings beds. The undrained shear strength of the beds varied between 0.008 and 0.975 kPa for effective stresses below 1.19 kPa and increased with depth. Correspondingly, the moisture content decreased with depth and varied between 17 and 27%. The factor controlling the undrained shear strength of the tested beds was the vertical effective stress, with the water content also having some secondary effect. The correlation between the undrained shear strength and the vertical effective stress was expressed with a second order polynomial function. Consolidation time did not appear to influence the observed shear strength.  相似文献   

Arsenic removal from aqueous solutions by mixed magnetite–maghemite nanoparticles     

Saidur Rahman Chowdhury  Ernest K. Yanful  Allen R. Pratt 《Environmental Earth Sciences》2011,64(2):411-423

In this study, magnetite–maghemite nanoparticles were used to treat arsenic-contaminated water. X-ray photoelectron spectroscopy (XPS) studies showed the presence of arsenic on the surface of magnetite–maghemite nanoparticles. Theoretical multiplet analysis of the magnetite–maghemite mixture (Fe₃O₄-γFe₂O₃) reported 30.8% of maghemite and 69.2% of magnetite. The results show that redox reaction occurred on magnetite–maghemite mixture surface when arsenic was introduced. The study showed that, apart from pH, the removal of arsenic from contaminated water also depends on contact time and initial concentration of arsenic. Equilibrium was achieved in 3 h in the case of 2 mg/L of As(V) and As(III) concentrations at pH 6.5. The results further suggest that arsenic adsorption involved the formation of weak arsenic-iron oxide complexes at the magnetite–maghemite surface. In groundwater, arsenic adsorption capacity of magnetite–maghemite nanoparticles at room temperature, calculated from the Langmuir isotherm, was 80 μmol/g and Gibbs free energy (∆G⁰, kJ/mol) for arsenic removal was −35 kJ/mol, indicating the spontaneous nature of adsorption on magnetite–maghemite nanoparticles.  相似文献   

Report of excursion to Cobham,Surrey: Weald research committee excursion     

Ernest A. Turner 《Proceedings of the Geologists' Association. Geologists' Association》1928,39(2):193-194

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Source potential and palynofacies of Late Jurassic “Lemeš facies”, Croatia     

Snježana Blažeković Smojić  Jasmin Smajlović  Georg Koch  Jeronim Bulić  Mladen Trutin  Ernest Oreški  Anđa Alajbeg  Vladimir Veseli 《Organic Geochemistry》2009,40(8):833-845

Laminated limestone and calcareous shale outcrop samples from the Late Jurassic “Leme?” facies (Croatia) were investigated to characterize their organic facies and palynofacies and their hydrocarbon generative potential. The results indicate that the organic rich sediments of “Leme?” facies were deposited within a relatively shallow marine environment at low redox potential, characterized as an oxygen depleted depositional setting with stratified bottom waters of the carbonate platform (Adriatic Carbonate Platform). The organic rich samples contain a high portion of lipid rich amorphous kerogen of algal/phytoplankton origin, enriched by bacterial biomass. Most of the analyzed samples have total organic carbon contents (TOC) greater than 3%, Rock-Eval S2 >20 mg HC/g rock, yielding Hydrogen Index (HI) values ranging from 509–602 mg HC/g TOC. According to these results, the analyzed samples have very good to excellent oil generative potential. Relatively high sulfur content suggests that the kerogen is best described as Type II-S. Biomarker maturity parameters, as well as the fluorescence of the isolated kerogen, show that the organic matter is at early to peak oil thermal maturity. The observed level of thermal maturity indicates that these samples were once buried to depths of ～5.5–5.8 km before being uplifted in the late Tertiary. The surface outcrops of the “Leme?” facies suggest that these strata have significant source potential and are the likely source of oil in the Croatian External Dinarides.  相似文献   

Turbulence characteristics in the atmospheric surface layer during summer monsoon of 1997 over a semi-arid location in India     

T. Dharmaraj  G. R. Chinthalu  P. Ernest Raj 《Meteorology and Atmospheric Physics》2009,104(1-2):113-123

A land surface processes experiment (LASPEX) was conducted in the semi-arid region of Northwest India during January 1997–February 1998. Analysis of turbulent components of wind and air temperature collected in the surface layer (SL) at Anand (22°35′N, 72°55′E) during the Indian summer monsoon season from June to September 1997 is presented. Turbulent fluctuation of wind components and air temperature observed at Anand varied as a function of terrain features and stability of the surface layer. Under neutral conditions, the standard deviation of vertical velocity (σ _w ) and temperature (σ _T ) were normalized using respective surface layer scaling parameter u _* and T _* which fitted the expressions σ _w /u _* = 1.25 and σ _T /T _* ≈ 4. Micrometeorological spectrum of wind and temperature at 5 m above ground level (AGL) at Anand showed peaks at time scale of 1–3 min at the low-frequency end. The inertial sub-range characteristics (?2/3 slope) of the spectrum are exhibited mostly. However, in some occasions, slope of ?1 denoting brown noise was depicted by the wind and temperature spectrum, which indicated anisotropy in turbulence.  相似文献   

Low-frequency dilatational wave propagation through fully-saturated poroelastic media     

Wei-Cheng Lo  Garrison Sposito  Ernest Majer 《Advances in water resources》2006

The strong coupling of applied stress and pore fluid pressure, known as poroelasticity, is relevant to a number of applied problems arising in hydrogeology and reservoir engineering. The standard theory of poroelastic behavior in a homogeneous, isotropic, elastic porous medium saturated by a viscous, compressible fluid is due to Biot, who derived a pair of coupled partial differential equations that accurately predict the existence of two independent dilatational (compressional) wave motions, corresponding to in-phase and out-of-phase displacements of the solid and fluid phases, respectively. The Biot equations can be decoupled exactly after Fourier transformation to the frequency domain, but the resulting pair of Helmholtz equations cannot be converted to partial differential equations in the time domain and, therefore, closed-form analytical solutions of these equations in space and time variables cannot be obtained. In this paper we show that the decoupled Helmholtz equations can in fact be transformed to two independent partial differential equations in the time domain if the wave excitation frequency is very small as compared to a critical frequency equal to the kinematic viscosity of the pore fluid divided by the permeability of the porous medium. The partial differential equations found are a propagating wave equation and a dissipative wave equation, for which closed-form solutions are known under a variety of initial and boundary conditions. Numerical calculations indicate that the magnitude of the critical frequency for representative sedimentary materials containing either water or a nonaqueous phase liquid is in the kHz–MHz range, which is generally above the seismic band of frequencies. Therefore, the two partial differential equations obtained should be accurate for modeling elastic wave phenomena in fluid-saturated porous media under typical low-frequency conditions applicable to hydrogeological problems.  相似文献   

Lidar and Sun photometer observations of atmospheric boundary-layer characteristics over an urban area in a mountain valley     

Nikolay Kolev  Ivan Grigorov  Ivan Kolev  P. C. S. Devara  P. Ernest. Raj  K. K. Dani 《Boundary-Layer Meteorology》2007,124(1):99-115

We present measurements of the vertical aerosol structure and the aerosol optical depth in the lower troposphere performed above the city of Sofia (an urban area situated in a mountain valley), western Bulgaria by means of a ground-based aerosol lidar operating continuously for a number of years. The lidar measurements were accompanied by measurements of the aerosol optical depth (AOD) in the visible and near infrared regions of the spectrum performed in October 2004 using Microtops II radiometers. The maximum values of the AOD were found to occur 1–2 h before the complete development of the atmospheric boundary layer, i.e. during the residual layer destruction, which confirms our hypothesis concerning the slope circulation effect on the processes taking place in the atmospheric boundary layer. The AOD values obtained by the lidar are lower than those taken by the sun photometer. Further, the AOD exhibits two different types of behaviour. In the case of a ‘clear atmosphere’ (i.e. in the absence of volcanic eruptions and/or dust transport from the Sahara) most of the aerosol accumulated within the atmospheric boundary layer over the urban area considered. The combined use of the two instruments allows the comparison between the optical characteristics of the atmospheric aerosol (e.g. aerosol extinction coefficient, etc.) obtained by the lidar and through an independent method (sun photometer).  相似文献   

Are interplanetary magnetic clouds manifestations of coronal transients at 1 AU?   总被引：2，自引：0，他引：2  

Robert M. Wilson  Ernest Hildner 《Solar physics》1984,91(1):169-180

Using proxy data for the occurrence of those mass ejections from the solar corona which are directed earthward, we investigate the association between the post-1970 interplanetary magnetic clouds of Klein and Burlaga (1982) and coronal mass ejections. The evidence linking magnetic clouds following shocks with coronal mass ejections is striking; six of nine clouds observed at Earth were preceded an appropriate time earlier by meter-wave type II radio bursts indicative of coronal shock waves and coronal mass ejections occurring near central meridian. During the selected control periods when no clouds were detected near Earth, the only type II bursts reported were associated with solar activity near the limbs. Where the proxy solar data to be sought are not so clearly suggested, that is, for clouds preceding interaction regions and clouds within cold magnetic enhancements, the evidence linking the clouds and coronal mass ejections is not as clear; proxy data usually suggest many candidate mass-ejection events for each cloud. Overall, the data are consistent with and support the hypothesis suggested by Klein and Burlaga that magnetic clouds observed with spacecraft at 1 AU are manifestations of solar coronal mass ejection transients.  相似文献   

Study on the Chemical Character of Water Soluble Organic Compounds in Fine Atmospheric Aerosol at the Jungfraujoch   总被引：1，自引：0，他引：1  

Zoltán Krivácsy  András Gelencsér  Gyula Kiss  Ernő Mészáros  Ágnes Molnár  András Hoffer  Tamás Mészáros  Zsolt Sárvári  Dóra Temesi  Bálint Varga  Urs Baltensperger  Stephan Nyeki  Ernest Weingartner 《Journal of Atmospheric Chemistry》2001,39(3):235-259

In this study the chemical nature of the bulk of water soluble organic compounds in fine atmospheric aerosol collected during summer 1998 at the Jungfraujoch, Switzerland (3580 m asl) is characterised. The mass concentration of water soluble organic substances was similar to those of major inorganic ions, and the water soluble organic matter was found to be composed of two main fractions: (i) highly polyconjugated, acidic compounds with a varying degree of hydrophobicity and (ii) slightly polyconjugated, neutral and very hydrophilic compounds. The contribution of both fractions to the total water soluble organic carbon was about 50%. Separation into individual components was impossible either by HPLC or capillary electrophoresis which indicates the presence of a high number of chemically similar but not identical species. Results obtained by ultrafiltration and HPLC-MS have shown that the molecular weights are of the order of several hundreds. Most of the protonation constants for the acidic compounds determined by capillary electrophoresis were in the range 10⁴–10⁷.  相似文献   

Seasonal variations in the vertical structure of water vapor optical depth in the lower troposphere over a tropical station     

P. Ernest Raj  P.C.S. Devara 《大气科学进展》1997,14(3):425-432

Spatio-temporal variations of water vapor optical depth in the lower troposphere (450-3850 m) over Punt (18o32’N, 73o51’E, 559 m Above Mean Sea Level), India have been studied over a period of five years. The mean ver-tical structure showed that the moisture content is greatest at the lowest level and decreases with increasing altitude, except in the south-west monsoon season (June to September) where an increase upto 950 m has been found. Optical depths are maximum in the monsoon season. The increase from pre-monsoon (March-May) to monsoon season in moisture content on an average is by about 58% in the above altitude range. The temporal variations in surface Rela-tive Humidity and optical depth at 450 m show positive correlation. The amplitude of seasonal oscillation is the larg-est at 1465 m altitude. The time-height cross-sections of water vapor optical depths in the lower troposphere showed a contrast between years of good and bad monsoon.  相似文献