Strength Properties of Sandy Soil–Cement Admixtures     

António Viana da Fonseca  Rodrigo Caberlon Cruz  Nilo Cesar Consoli 《Geotechnical and Geological Engineering》2009,27(6):681-686

Soil stabilization with cement is a good solution for the construction of subgrades for roadway and railway lines, especially under the platforms and mostly in transition zones between embankments and rigid structures, where the mechanical properties of supporting soils are very influential. These solutions are especially attractive in line works where other ground improvement techniques are extensive and, therefore, very expensive. On the other hand, the economic and environmental costs of such works should be optimized with good balances between excavation and embankment volumes. For this purpose, the improvement of locally available soils can bring great advantages, avoiding a great amount in borrowing appropriate material, as well as the need of disposing huge volumes in deposits. This paper focus on the characteristics of two soils, Osorio sand and Botucatu residual sandstone, which can be converted to well acceptable materials for this purpose, if stabilized with cement. The study of soil stabilization with cement relies on the quantification of the influence of percentage of cement and porosity adopted in the admixing process for different state and stress conditions. This influence will be evaluated from the analysis of unconfined compression strength (UCS or q _u ) test results. This experimental framework will enable a good definition of mechanical parameters used in design of foundations and subgrades of railways platforms and for their execution quality control.  相似文献   

Middle Ordovician subduction of continental crust in the Scandinavian Caledonides: an example from Tjeliken,Seve Nappe Complex,Sweden     

Kathrin?FassmerEmail author  Iwona?Klonowska  Katarzyna?Walczak  Barbro?Andersson  Nikolaus?Froitzheim  Jaros?aw?Majka  Raúl?O.?C.?Fonseca  Carsten?Münker  Marian?Janák  Martin?Whitehouse 《Contributions to Mineralogy and Petrology》2017,172(11-12):103

The Seve Nappe Complex of the Scandinavian Caledonides is thought to be derived from the distal passive margin of Baltica which collided with Laurentia in the Scandian Phase of the Caledonian Orogeny at 430–400 Ma. Parts of the Seve Nappe Complex were affected by pre-Scandian high- and ultrahigh-pressure metamorphism, in a tectonic framework that is still unclear, partly due to uncertainties about the exact timing. Previous age determinations yielded between ~ 505 and ~ 446 Ma, with a general trend of older ages in the North (Norrbotten) than in the South (Jämtland). New age determinations were performed on eclogite and garnet–phengite gneiss at Tjeliken in northern Jämtland. Thermodynamic modelling yielded peak metamorphic conditions of 25–27 kbar/680–760 °C for the garnet–phengite gneiss, similar to published peak metamorphic conditions of the eclogite (25–26 kbar/650–700 °C). Metamorphic rims of zircons from the garnet–phengite gneiss were dated using secondary ion mass spectrometry and yielded a concordia age of 458.9 ± 2.5 Ma. Lu–Hf garnet-whole rock dating yielded 458 ± 1.0 Ma for the eclogite. Garnet in the eclogite shows prograde major-element zoning and concentration of Lu in the cores, indicating that this age is related to garnet growth during pressure increase, i.e. subduction. The identical ages from both rock types, coinciding with published Sm–Nd ages from the eclogite, confirm subduction of the Seve Nappe Complex in Northern Jämtland during the Middle Ordovician in a fast subduction–exhumation cycle.  相似文献   

Environmental issues in urban groundwater systems: a multidisciplinary study of the Paranhos and Salgueiros spring waters,Porto (NW Portugal)   总被引：1，自引：1，他引：0  

Maria José Afonso  Helder I. Chaminé  José M. Marques  Paula M. Carreira  Laura Guimarães  Lúcia Guilhermino  Alberto Gomes  Paulo E. Fonseca  Ana Pires  Fernando Rocha 《Environmental Earth Sciences》2010,61(2):379-392

This study presents the results of a multidisciplinary approach, using hydrogeochemical, isotopic and ecotoxicological analyses, performed to assess the nature and suitability for use of Paranhos and Salgueiros spring waters (Porto city, NW Portugal). Based on the surface activities located along the course of the springs, 23 water samples were collected. All the samples were analysed for major element concentrations. The isotopic techniques employed included δ²H, δ¹⁸O and ³H. Standard acute bioassays with Daphnia magna were also performed. The hydrogeochemical analyses showed a nitrate and sulphate-enriched composition for these groundwaters, resulting mainly from urban drainage and sewer leakage. In the ecotoxicological analyses, no significant mortality was observed in any of the tests performed. The results obtained in this study suggest that Porto urban groundwater could be suitable for irrigation uses.  相似文献   

Phosphorus dynamics in water and sediments in urbanized and non-urbanized rivers in Southern Brazil   总被引：1，自引：0，他引：1  

Pagliosa PR  Fonseca A  Bosquilha GE  Braga ES  Barbosa FA 《Marine pollution bulletin》2005,50(9):965-974

Phosphorus flux models show that the removal tends to be a common feature in polluted estuarine systems whereas the release of P to the adjacent coastal area occurs in pristine environments. This study analyzes the distribution of P in water and sediments along six rivers in the south coast of Brazil. Three rivers located inside protected areas were considered non-polluted and used as a control of urbanization. The other three, situated within urbanized areas, were considered as having highly elevated concentrations of P. Results showed a different behavior of P in water and sediments located in urbanized and non-urbanized areas. The concentrations of dissolved organic (P-org) and inorganic (P-inorg) phosphorus in water, and the total phosphorus (P-tot) and polyphosphate (P-poly) in sediments where higher in the urbanized rivers compared to the non-urbanized ones. Both P of punctual origin and of diffuse origin contributed to the maintenance of elevated concentrations and disturbed the natural fluxes along the polluted rivers. The minimum and maximum concentrations in urbanized areas varied from 0.39 to 12.45 (microM) for P-org and 0.00 to 5.92 (microM) for P-inorg in water, and in sediments from 89.90 to 808.16 (microM g(-1)) for P-tot and 0.00 to 76.51 (microM g(-1)) for P-poly. In non-urbanized areas concentrations in water varied from 0.22 to 1.20 (microM) for P-inorg and 4.43 to 5.56 (microM) for P-org, and in sediments from 45.91 to 652.26 (microM g(-1)) for P-tot and 0.00 to 8.61 (microM g(-1)) for P-poly. Using a hierarchical sampling design and a simple model of variation of P (K(d) model) it was possible to demonstrate that urbanized and non-urbanized estuaries may act as sinks or sources of P. The variation of P analysis in different points along each of the six rivers showed that release and removal areas may occur within a same river independently of its urbanization.  相似文献   

Tectonics of the Beja-Acebuches Ophiolite: a major suture in the Iberian Variscan Foldbelt     

P. Fonseca  A. Ribeiro 《International Journal of Earth Sciences》1993,82(3):440-447

The Beja-Acebuches Ophiolitic Complex (BAOC) (south Portugal/Spain) corresponds to a high grade metamorphic belt along the boundary between Ossa-Morena and the South Portuguese Zones and comprises a lithostratigraphic sequence including (from top to bottom) metabasalts, (metamorphosed) multiple dyke intrusions in gabbro, flasergabbros and metaserpentinites. It is affected by three deformation phases. D₁ affects the ophiolite lower stratigraphic units and is represented by a mylonitic cleavage with a stretching lineation where shear criteria indicates the sense of shear to be towards the north-north-east; this deformation event can be related to the ophiolite emplacement above the crystalline footwall of the Serpa antiform, affecting Precambrian basement and Cambrian cover rocks. The obduction polarity ist north-eastwards, similar to the subduction polarity that generates the Beja Gabbroic Complex (BGC), implying a flake geometry. The second deformation phase, D₂, is represented by an intense WNW-ESE sinistral shear event which is responsible for the shattered appearance of the suture; D₂ is reactivated later by a more brittle D₃ event involving thrusting to the south-west, again with a sinistral component. ⁴⁰Ar/³⁹Ar isotopic ages were obtained for (metamorphosed) multiple dyke intrusions in the BAOC's gabbro (342.6 ± 1.4 Ma), for metagabbroic cumulates (340.7 ± 1.9 Ma), and for the undeformed/unmetamorphosed BGC (341.1 ± 1.3 Ma) occurring to the north of the ophiolitic suture. These ages reflect a last regional cooling event in the area which post-dates the ophiolite emplacement and the intrusion of the BGC through this oceanic sequence. Correspondence to: P. Fonseca  相似文献   

Oxygen solubility and speciation in sulphide-rich mattes     

Raúl O.C. Fonseca  Ian H. Campbell  John D. Fitzgerald 《Geochimica et cosmochimica acta》2008,72(11):2619-2635

Sulphide-rich liquids are common in magmatic environments forming over a wide range of temperature, pressure, fO₂ and fS₂. They are economically important because they sequester valuable metals such as Cu, Ni, Au and Pt from silicate melts. The presence of accessory amounts of primary oxides associated with sulphide mineralisations is often ignored or unexplained. Experimental work has shown that large amounts of oxygen can dissolve into mattes at fO₂ typical of terrestrial environments. At the quartz-fayalite-magnetite fO₂ buffer, the molar fraction of O in the matte exceeds that of S, placing the composition of the matte to the magnetite side of the mss (monosulphide solid solution)-magnetite join in the Fe-S-O system. However, sulphides crystallise before magnetite in most sulphide mineralisations and are much more abundant. Moreover, the speciation of O in a matte is not well known. Here we report the results of an experimental study of the solubility of O in mattes as a function of fS₂, fO₂, temperature, and composition. We confirm previous observations that Ni and Cu have a negative effect on the solubility of O in mattes. We show evidence for the existence of FeSO as a structural constituent of mattes in the Fe-S-O system. We present a simple parameterisation of the amount of O dissolved in mattes under relevant geological conditions, and use this parameterisation to discuss mechanisms for the crystallisation of primary spinels associated with sulphides in the Kambalda massive sulphide deposit (Western Australia) and the Sudbury Igneous Complex (Ontario, Canada).  相似文献   

New approaches to environmental monitoring: the use of ICT to explore volunteered geographic information   总被引：3，自引：0，他引：3  

Cristina Gouveia  Alexandra Fonseca 《GeoJournal》2008,72(3-4):185-197

Citizen participation in environmental monitoring is not a new idea. However, recent developments in information and communication technologies (ICT), such as the social web and the miniaturization of sensors, have created new opportunities to promote citizen participation in environmental monitoring. The analysis of existing citizen initiatives that use ICT tools, identified the need for a framework conceptualizing ways to increase the contribution of volunteered geographic data in environmental monitoring. Environmental Collaborative Monitoring Networks (ECMN) are proposed in this paper as a framework that combines the concepts of traditional environmental monitoring networks with the ideals of the open source movement. Such framework can guide the creation of fixed and mobile monitoring networks and is organized based on three building blocks: (1) Motivated Citizens; (2) Sensing Devices; and (3) Back-End Information Infrastructure. To illustrate the issues involved in the implementation of the building blocks of ECMN, the Senses@Watch project is presented, which explored the use of sensory data as a source of monitoring data.  相似文献   

Columnar joints in the Patino Formation sandstones, Eastern Paraguay： a dynamic interaction between dyke intrusion, quartz dissolution and cooling-induced fractures     

Victor Fernandez Velazquez Paulo Cesar Fonseca Giannini Claudio Riccomini Alethea Ernandes Martins Sallun Jorge Hachiro Celso de Barros Gomes 《《幕》》2008,31(3):302-308

The Patiho Formation sandstones, which crop out in Aregud neighborhood in Eastern Paraguay and show columnar joints near the contact zone with a nephelinite dyke, have as their main characteristics the high pro- portion of syntaxial quartz overgrowth and a porosity originated from different processes, initially by dissolu- tion and later by partial filling and fracturing. Features like the presence of floating grains in the syntaxial cement, the transitional interpenetrative contact between the silica-rich cement and grains as well as the intense fracture porosity are strong indications that the cement has been formed by dissolution and reprecipita- tion of quartz from the framework under the effect of thermal expansion followed by rapid contraction. The increase of the silica-rich cement towards the dyke in association with the orthogonal disposition of the columns relative to dyke walls are indicative that the igneous body may represent the main heat source for the interstitial aqueous solutions previously existing in the sediments. At macroscopic scale, the increasing of inter- nal tensions in the sandstones is responsible for the nucleation of polygons, leading to the individualization of prisms, which are interconnected by a system of joints, formed firstly on isotherm surfaces of low tem- perature and later on successive adjacent planes towards the dyke heat source.  相似文献   

High efficacy on diclofenac removal by activated carbon produced from potato peel waste     

M. Bernardo  S. Rodrigues  N. Lapa  I. Matos  F. Lemos  M. K. S. Batista  A. P. Carvalho  I. Fonseca 《International Journal of Environmental Science and Technology》2016,13(8):1989-2000

In the present study, a novel porous carbon obtained by K₂CO₃ activation of potato peel waste under optimized conditions was applied for the first time as liquid-phase adsorbent of sodium diclofenac in parallel with a commercial activated carbon. The biomass-activated carbon presented an apparent surface area of 866 m² g^?1 and well-developed microporous structure with a large amount of ultramicropores. The obtained carbon presented leaching and ecotoxicological properties compatible with its safe application to aqueous medium. Kinetic data of laboratory-made and commercial sample were best fitted by the pseudo-second-order model. The commercial carbon presented higher uptake of diclofenac, but the biomass carbon presented the higher adsorption rate which was associated with its higher hydrophilic nature which favoured external mass transfer. Both adsorbents presented adsorption isotherms that were best fitted by Langmuir model. The biomass carbon and the commercial carbon presented adsorption monolayer capacities of 69 and 146 mg g^?1, and Langmuir constants of 0.38 and 1.02 L mg^?1, respectively. The better performance of the commercial sample was related to its slightly higher micropore volume, but the most remarkable effect was the competition of water molecules in the biomass carbon.  相似文献   

Assessment of human effects through phosphorus partitioning in sediments from two catchment basins around Guanabara Bay,SE Brazil     

Carlos Marclei Arruda Rangel  José Antônio Baptista Neto  Priscilla Soares de Oliveira  Luciana Gomes Lima  Estefan Monteiro da Fonseca 《Environmental Earth Sciences》2016,75(17):1215

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