1,720,957 research outputs found
Geotechnical characterization of the soils along the alignment of Montedoglio-Lake Trasimeno water pipe (Central Italy).
No full textThe Lake Trasimeno is one of the major Italian lakes and its economic and environmental significance is quite great. In the last years, the anthropic pressure effects became, though
enhanced, only incidental to the consequences of a dry climatic phase that led to a drastic reduction in the lake water levels which are strictly influenced by rainfall rather than by groundwater flows. After the last water crisis (2002-2003 period) a water pipeline from Montedoglio dam to lake Trasimeno (Tuscany-Umbria border) was planned with the purpose to regulate the lake levels and to satisfy the agricultural water demand of Chiana valley. This note gives the results of the geotechnical and mineralogical characterization of some Pleistocene-Holocene fluvial-lacustrine soils found on the test trenches excavated along the 3th lot of the water pipeline (21 km long). About fourteen samples were analyzed along the alignment in order to verify the suitability of the soils as materials of covering and to correlate the geotechnical and mineralogical parameters with other clayely soils of central Italy (Umbria region). Ten samples belong to groups A4 and A6 of the CNR UNI 10006 (silts and not very compressible clays), two of them belong to A2-4 (gravels and silty sands), and only one (C4) belongs to group A7-5 (highly compressible clays of medium plasticity). According to the modified Skempton diagram, all the samples align with the kaolinite line and, unlike other soils of fluvial-lacustrine origin from the Chiana valley, they show a medium-low swelling potential. An analysis of the Proctor curves shows how the samples generally have a maximum dry density ranging between 2.07 and 1.95 g/cm3, while the optimum moisture content varies between 8.6 and 11.4%. The C4 sample differs from the rest, showing a much broader curve, with moisture content values from 12% to 20% and a maximum dry density value of 1.76 g/cm3. In conclusion, the soils found along the alignment can be considered suitable for covering the water pipe, except for those from the area where sample C4 was taken. Consequently, if the soils in question are used, since both the organic carbon content and the sulfates content are suitable, it is recommended their lime stabilization in order to reduce the problems connected with swelling
Laboratory shear strength parameters of cohesive soils: variability and potential effects on slope stability
No full textThe study quantified laboratory geotechnical variability by analyzing compacted alluvial fine-grained soils commonly used to backfill exhausted quarries in Central Italy. Repeating the test 4 times and combining the relevant results, 256 pairs of friction angle and cohesion values were obtained, with mean values of 27.0°±0.8° and 19.22±4.08 kPa, respectively in the shear stress range 100–250 kPa. The influence of the variability of laboratory drained shear strength parameters on the long-term stability of artificial saturated slopes was examined, taking into account both deterministic and probabilistic approaches. In many cases, when the deterministic approach indicates stability, the probabilistic one indicates a certain probability of instability, even for the lowest slope height (5 m) and a slope angle higher than 15°
Compressibility of Kaolinitic Clay Contaminated by Ethanol-Gasoline Blends
No full textIn this work, oedometer tests were used to examine the effects of ethanol-gasoline blends on the consolidation characteristics of a kaolinitic soil from northwestern Spain. As the fraction of ethanol in blends increases, the equivalent liquid limit of soil decreases, showing a dividing point for blends containing about 85% of ethanol. By means of a database of compression indexes of remolded clayey soils mixed with differing kinds of alcohol and petroleum hydrocarbon contaminants, a multivariable model for estimating the compression index of the contaminated soil is presented, on the basis of the virgin compression index, normalized liquid limit, and normalized pore fluid viscosity. The model is valid only for percentages of active clays up to 10–15% in weight in kaolinitic soil. The authors would like to encourage others to further validate and refine the approach, which may be useful for preliminary estimation of the compression index of contaminated soils, reducing operators’ risk of inhaling vapors released by the ethanol-gasoline blends while performing the test and also reducing damage to conventional oedometer equipment. This manuscript was submitted on May 27, 2010; approved on December 8, 2010; published online on December 10, 2010. 2011 American Society of Civil Engineers. CE Database subject headings: Gasoline; Soil pollution; Clays
Effect of laboratory repeatability of direct shear test on slope stability
No full textThe present work quantified the laboratory geotechnical variability by repeatability direct shear test (DS) on alluvial fine-grained soils. The effect of laboratory variability of geotechnical parameters (cohesion c’ and friction angle φ’) on slope stability was investigated. A mixture of compacted fine sand (40%) and clayey silt (60%) taken from a quarry fines stockpile was used: these soils are commonly used to backfill exhausted quarries located in the River Paglia alluvial plain (Central Italy). As knew in the literature, the dry density achieved by a given degree of compaction controls the shear strength parameters affecting the performance of compacted soil. Four direct shear tests were conducted following the ASTM D 3080-72 procedure on samples having a dry density of about 16.5 kN/m3, corresponding to 95 % of maximum dry density. Combining four DS tests yielded 256 pairs of shear strength parameters in terms of effective stresses, φ’ and c’ parameters show normal distribution with φ’= 27.0 ± 0.8° and c’= 19.22 ± 4.08 kPa, for the stress range 100÷250 kPa. In most of the 256 combinations, the friction angle decreased as the cohesion increased. It is generally accepted that the strength parameters (c’ and φ’) have a negative correlation, although it is appreciated this is not always the case and different cohesion values can be obtained for the same friction angle (i.e., for the same slope of Coulomb failure envelope). The effect of the uncontrolled experimental variability of shear strength parameters on the long-term stability of a single homogeneous slope whose geometry can vary was investigated. Analyzing the factor of safety obtained using all the 256 combinations of shear strength parameters, the probability of having safety factors lower than 1.30 for the different slope heights was calculated. Such analyses demonstrate not only that direct shear testing is reliable, but also that the stability of a slope can be assessed with greater accuracy
Effects of fall-cone test on classification of soils: some considerations from study of two engineering earthworks in Central Italy
No full textThis work, based on the data of two earthworks recently completed on two sites near Lake Trasimeno (Central Italy), examines the consequences of the
enforcement in Europe of the fall-cone test for the Liquid Limit (LLcone) instead of the Casagrande cup (LLcup). This
new standard has been incorporated in the latest Italian soil classification (UNI 11531-1:2014), substituting the previous
one (UNI 10006:2002). A set of 28 soil samples was analysed: the research shows that LLcone is always greater
than LLcup. According to the old standard, all samples were suitable for the works planned but, according to the new
one, 18 % of samples became unsuitable. This is in spite of the fact that there is nothing to show that the old classification
was ‘‘unsafe.’’ The new standard (based on LLcone) restricts the choice of materials, so that not only will costs
for earthworks increase in the future but, paradoxically, because of the new standard, thousands of kilometers of
properly working old leve ́es became suddenly ‘‘unsafe.’’ The results suggest that soil classification criteria for earthworks should be reconsidered in order to transform the
conventional ‘‘index properties’’ to sound physical characteristics
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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