1,721,017 research outputs found
Assessing River Embankment Stability Under Transient Seepage Conditions
No full textAbstractThe evaluation of riverbank stability is a fundamental problem in flood risk management, representing a critical task for engineering practice. Soil heterogeneity together with initial and boundary conditions are among the crucial issues that should be considered to obtain an accurate solution of the problem. Generally, attention and efforts are mostly devoted to the soil characterization, the hydrometric level forecasts and the estimation of the rainfall intensity, while in situ measurements usually receive less attention. Nevertheless, suction and soil water content have a strong influence on the reliability of seepage and stability analyses. A preliminary study aiming at the design of a monitoring system for the measurement of soil moisture and suction in the unsaturated silty soils of a river embankment has been carried out, with the purpose of linking the collected data to the boundary conditions and hence obtaining a more accurate estimate of the riverbank probability of failure. Furthermore, a general outline of the research project, its methodology and application are presented in the paper
STRUMENTO DI VERIFICA DEL GRADO DI SATURAZIONE DI UN GRUPPO SENSORE DI PRESSIONE DI UN PIEZOCONO, E METODO PER EFFETTUARE TALE VERIFICA
No full textL’invenzione ha ad oggetto uno strumento di verifica del grado di saturazione di un gruppo sensore di pressione di un piezocono, e un metodo per effettuare tale verifica. Il metodo e l'apparecchiatura stabiliscono un criterio quantitativo per definire il grado di saturazione della punta di un piezocono, e conseguentemente l’affidabilità delle misure ottenute. La procedura, da realizzarsi prima della prova, può efficacemente essere utilizzata anche al termine di questa, al fine di verificare l’insorgere di eventuali fenomeni di desaturazione nel corso della prova, dovuti all’attraversamento di strati di terreno non saturi o per venute di gas
Ancient to modern metallurgical slags: evolving smelting techniques and their interaction with the environment
No full textThe discovery of metals and how to extract and use them was a turning point in human history, because it changed the economy and socio-cultural structure of ancient civilisations and started to severely affect the impact of human activities on the environment. In fact, a lot of societies developed near extraction sites and founded their economy on the use and trade of metals.
In Tuscany (Italy) there has been a long history of mining and metal extraction. From archaeological studies it has been reconstructed that the earliest records of these activities date back to the Etruscan period (VII century B.C.). Exploitation continued intermittently until a few decades ago. This extended period of mining exploitation left a wealth of both iron and copper metallurgical slags that can usually be found as abandoned and unsupervised heaps.
These slags, apparently just a waste from the metallurgical process, actually carry information about the evolution of the metallurgical process through which they were generated. Information about the charge, flux and fuel can be inferred from chemical and mineralogical composition of the slags.
Slags from three different smelting districts, ranging from ancient Etruscan-Roman period to modern age (1900 A.D.) were studied macroscopically, identifying distinctive features related to the smelting process in different time periods. Then, thin sections obtained from representative samples were examined, using optical microscopy and electron microscopy. Chemical analyses were performed for major and trace elements by X-ray fluorescence spectroscopy and by inductively coupled plasma mass spectrometry, respectively.
Leaching experiments on some carefully selected samples were also completed, to investigate the release of potentially toxic elements during the interaction of the slags with the surrounding environment.
This kind of investigation allows to reconstruct part of the history of metal utilisation as well as to predict the impact that these remains will have on the environment
Influence of grading and mineralogy on the behaviour of saprolites
No full textSoils originating from chemical decomposition do not undergo any sorting in their grading resulting in a well-graded material. Their composition may be influenced by weathering in one or more aspects, e.g. particle size, particle size distribution, mineralogy or particle morphology. Each of these aspects and their effects on the mechanical behaviour have been studied separately in the past. To identify the dominant parameters a series of standard oedometer tests was carried out to investigate the influences of the grading and mineralogy on the Normal Compression Line (NCL) separately. This was achieved taking the most and least decomposed granite sampled at a same location and reconstituting them to the same grading to study the influence of mineralogy or reconstituting one of them to both the gradings to study that of grading. In the first case, the NCLs were practically coincident, while in the second they were further apart, showing that the grading has greater importance in determining the mechanical behaviour in compression
Experimental weathering of historical slags exposed to rhizosphere-like organic acids and various pH conditions
No full textRecovery of sulfur from sulfur-rich filter cakes in a rotary kiln: Process optimization
No full textIn this work, sulfur recovery from sulfur-rich wastes deriving from sulfur filtration was investigated through laboratory experiments and full-scale tests in an industrial combustion rotary kiln, where elemental sulfur is converted to SO2 in a sulfuric acid production plant. Phase equilibria experiments carried out in the temperature range 1100–1400 °C and industrial scale tests demonstrated that temperature is the most important operating parameter in determining the recovery efficiency and the plant operability. The full-scale tests performed on the rotary kiln showed that, at operating temperatures around 1200 °C, a continuous sulfur recovery from the filter cakes was obtained with an average efficiency of 87% and a consequent reduction of about 70% of the solid waste material to be disposed as inert in landfills or used in cement/glass industries. The efficiency of sulfur recovery increases with the increasing operating temperature but, above 1300 °C, the melting of the residual Ca-Fe-Al-silicate phase and the eventual recrystallization at the kiln refractory walls occurred, causing a forced plant shutdown.
The chemical-physical interaction between the sulfur-rich filter cake and different refractory materials was further investigated in the temperature range 1100–1300 °C. At the recommended operation temperatures of 1100–1200 °C, the interaction between the refractory material and the combustion ashes is negligible for all tested materials. Nonetheless, the use of Fe- and Cr-free refractory materials for the internal lining of the kiln must be preferred to minimize the deposition/adhesion of Ca-Fe-Al-silicates derived from combustion over long-term operation
A Multidisciplinary Tool for the Development of a Regional-scale Geotechnical Model: A Case Study in the North-Western Adriatic Coastal Area
No full textAbstractThe paper describes the geotechnical model of a coastal flat area facing the Adriatic Sea, between the municipalities of Cesenatico and Bellaria-Igea Marina (Emilia-Romagna region, Italy). On the basis of a large experimental database provided by the Geological, Seismic and Soil Survey of the Emilia-Romagna Authority, a stratigraphic scheme of the upper 40 m of this coastal plain subsoil has been defined and reliable estimates of parameters for the different soil units have been derived. The accurate mechanical characterization of soils, also reflecting their sedimentological framework, allows the development of a regional-scale geotechnical model providing a reliable and useful support to geotechnical engineers working in this area or similar geological environments
A new interparticle friction apparatus for granular materials
No full textA new apparatus is described that measures interparticle friction between sand-sized grains over relatively large displacements and also under immersion in a fluid. Its relatively simple design allows the key calibrations to be checked by statics. An analysis of the geometry of simple spherical particle contacts and the forces at those contacts revealed that there are strict constraints on the permissible stiffness of the interparticle friction apparatus to avoid stick-slip behaviour. Tests on ball bearings gave highly repeatable data, while others on glass ballotini revealed a significant effect of ambient humidity on the data obtained. The interparticle friction was found to increase with the roughness of the ballotini. Immersion in water increased the interparticle friction slightly for both the ballotini and quartz sand particles, while immersion in oil reduced the friction considerably for the quartz sand, especially at higher contact force levels
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