Results 1 - 10 of 48908
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[en] The Chernobyl post-accident scenario became nowadays a natural radioecology laboratory, where a wide range of decontamination methods can be applied, validated or developed. This paper presents the application of a soil rehabilitation technique, the removal of vegetation and associated soil, in the experimental fields of Bourakovka and Chistogalovka surrounding the Chernobyl NPP. The results obtained have shown soil decontamination factors higher than 90% for caesium and strontium. This technique involves the removal of deposited hot particles released at the accident, and the experience allowed a detailed study of one of them corresponding to a nuclear fuel fragment, probably generated at the beginning of the breakdown. 16 refs. (Author)
[en] The problem associated with black cotton and lateritic soils because of the swelling-shrinkage property of their constituent clay minerals were investigated. Samples of black cotton lateritic soils were collected from different parts of Kenya. The samples were analysed for their mineral compositions and later treated with hydrated lime in order to eliminate the swelling shrinkage behaviour. The samples were subsequently tested for their engineering properties in a soil mechanics laboratory using shear box and Casagrande apparatus. It was found that the chemical treatment of the soils with hydrated lime removes their plastic property and improves their shear strength. (author)
[en] A mathematical model capable of describing the soil behavior under any loading conditions, monotonic or cyclic, is presented within the framework of critical state soil mechanics. (orig.)
[en] With reference to the well known difficulty of quantifying non point phosphorous loads, as well as to their growing relative importance where point source leads decrease, a literature review has been carried out concerning soil export coefficients. On such basis, the values which seem to be the most appropriate for Italy have been estimated for different land use categories. The main mechanisms determining non point phosphorous load generation and the factors affecting their importance are also described. In the end, criteria for estimating the importance of non point sources in a basin are suggested to be used for deciding whether a traditional, parametric assessment (inevitably involving a certain error) can be acceptable or experimental measures are needed
[en] In this study, a clayey soil classified as A-7-5 according ASTM D3282, was stabilized using alkali-activated cementitious materials (AAC) added to the soil dry in percentages of 20 and 30%. Fly ash (F1, F2) with high unburned carbon content (up to 38.76%), hydrated lime (L) and granulated blast furnace slag were used. Unconfined compressive strength and flexural strength at 28 days of curing and the durability after 12 wetting-drying cycles were evaluated. The results were compared with a soil-cement reference mixture. The soil treated with AAC-F1L showed a volume expansion of 0.51% and volume contraction of -0.57% compared with the 0.59% expansion and -0.68% contraction of the soil-cement reference mixture. Additionally, the mass loss after the wetting and drying cycles is only 3.74% which is slightly lower than the mass loss of the soil stabilized with ordinary Portland cement (OPC) (3.86%) and well below the value specified in Colombian regulations (7%).
[es]En este estudio, un suelo arcilloso clasificado como A-7-5 según ASTM D3282, se estabilizó utilizando materiales activados alcalinamente (AAC) en porcentajes de 20 y 30%. Se utilizaron cenizas volantes (F1, F2) con alto contenido de inquemados (hasta 38,76%), cal hidratada (L) y escoria granulada de alto horno. Se evaluó la resistencia a la compresión confinada y la resistencia a la flexión a 28 días de curado y la durabilidad después de 12 ciclos de humectación-secado. Los resultados se compararon con una mezcla de referencia suelo-cemento. El suelo tratado con AAC-F1L mostró una expansión y contracción volumétrica del 0,51% y -0,57% respectivamente, en comparación con el 0,59% y -0,68% de la mezcla de referencia suelo-cemento. Además, la pérdida de masa después de los ciclos de humectación y secado es sólo 3.74%, valor ligeramente inferior a la del suelo estabilizado con cemento Portland (3.86%) y muy inferior al valor especificado en la normativa colombiana (7%).
[en] A discussion of various physical chemical questions which are associated with the quantitative analysis of water in earth materials is presented. A pseudothermodynamic approach to the binding of water in various types of earth materials is also presented. Emphasis is placed on the fact that as pore, crack, or hole sizes approach molecular dimensions, the interaction energy of water with the host material can become very large. A scale of interaction energies is suggested which would be useful for specifying operationally relevant analyses in earth materials. (author)
[en] The areas covered by the volcanic tephras Tierra Blanca Joven (TBJ) in El Salvador, was suffered mass movements, liquefaction and erosion during the rainy season or when major earthquakes occur, causing important environmental, social and economic losses. A pressure plate, centrifuge and filter paper were used to build a Soil-Water Retention Curve, obtain the characterization of these unsaturated soil, suction values of the fall unit of TBJ. The use of this curve into finite elements software can help to acquire shear strength and permeability properties. The filter paper showed to be a practical method but close to saturation the pressure plate is needed.Scatter results were observed with the centrifuge. The Quickdraw tensiometre (suction) and TMS3 (soil moisture content) are being used in field test to proposed a field methodology for an early warning system for the slopes, that could help in urban planning and risk assessment. (author)
[en] In order to partly fill the thermal soil properties studies, we focused this work in the relation between thermal and hydrodynamic soil properties for several soil textural classes. This study was divided in two different objective; (i) to determine and to analyze soil thermal and hydrodynamic properties, and (ii) to explore the impacts of hysteresis on soil thermal properties under experimental controlled conditions. Samples were obtained from Llobregat delta plain (Spain). To measure soil thermal properties, simple needle sensors were used. The samples were repacked in a soil column device. Volumetric water content and thermal conductivity were monitored continuously. The results allowed a rather complete understanding of the relation between thermal and hydrodynamic properties at laboratory scale for silt loam soils. Differences in thermal properties at a given water content were interpreted as a results of different hysteretic paths observed, arising in turn from different wetting and drying processes. (Author) 14 refs.
[en] Six tillage treatments were evaluated, from one with the completely powdered soil until one with zero removal, in order to establish the pertinent relationships among the condition of the soil, quantified by means of the determination of some of their physic-mechanics, properties the answer of a vegetable species (corn) to such conditions and the preservation of the resources water and soil in the time. The systems of smaller soil movement showed interesting indexes of conservation of the soil and of the water, at the time that the treatments of more removal presented better answers of the cultivation, but they pointed out an uncertainty of the soil that should revert such a situation in the future. The content of humidity and the resistance to the penetration, parameters that showed a bigger sensibility to the condition of the soil for effect of the preparation systems, were reason why they should be considered high-priority in the elaboration of tillage models