1,720,974 research outputs found
Function of permeable geosynthetics in unsaturated embankments subjected to rainfall infiltration
No full textInvestigation on parameters used in warning systems for rain-induced embankment instability
No full textA number of instrumented laboratory-scale soil embankment slopes were subjected to artificial rainfall until they failed. The factor of safety of the slope based on real-time measurements of pore-water pressure (suction) and laboratory measured soil properties were calculated as the rainfall progressed. Based on the experiment measurements and slope stability analysis, it was observed that slope displacement measurements can be used to warn the slope failure more accurately. Further, moisture content/pore-water pressure measurements near the toe of the slope and the real-time factor of safety can also be used for prediction of rainfall-induced embankment failures with adequate accuracy.\u
Direct shear testing on unsaturated silty soils to investigate the effects of drying and wetting on shear strength parameters at low suction
No full textA modified conventional direct shear device was used to measure unsaturated shear strength of two silty soils at low suction values (0 ~ 50 kPa) that were achieved by following drying and wetting paths of soil water characteristic curves (SWCCs). The results revealed that the internal friction angle of the soils was not significantly affected by either the suction or the drying wetting SWCCs. The apparent cohesion of soil increased with a decreasing rate as suction increased. Shear stress-shear displacement curves obtained from soil specimens subjected to the same net normal stress and different suction values showed a higher initial stiffness and a greater peak stress as suction increased. A soil in wetting exhibited slightly higher peak shear stress and more contractive volume change behavior than that of soil in drying at the same net normal stress and suction
Laboratory measurement of hydraulic conductivity functions of two unsaturated sandy soils during drying and wetting processes
No full textAbstractThe importance of applying unsaturated soil mechanics to geotechnical engineering design has been well understood. However, the consumption of time and the necessity for a specific laboratory testing apparatus when measuring unsaturated soil properties have limited the application of unsaturated soil mechanics theories in practice. Although methods for predicting unsaturated soil properties have been developed, the verification of these methods for a wide range of soil types is required in order to increase the confidence of practicing engineers in using these methods. In this study, a new permeameter was developed to measure the hydraulic conductivity of unsaturated soils using the steady-state method and directly measured suction (negative pore-water pressure) values. The apparatus is instrumented with two tensiometers for the direct measurement of suction during the tests. The apparatus can be used to obtain the hydraulic conductivity function of sandy soil over a low suction range (0–10kPa). Firstly, the repeatability of the unsaturated hydraulic conductivity measurement, using the new permeameter, was verified by conducting tests on two identical sandy soil specimens and obtaining similar results. The hydraulic conductivity functions of the two sandy soils were then measured during the drying and wetting processes of the soils. A significant hysteresis was observed when the hydraulic conductivity was plotted against the suction. However, the hysteresis effects were not apparent when the conductivity was plotted against the volumetric water content. Furthermore, the measured unsaturated hydraulic conductivity functions were compared with predictions using three different predictive methods that are widely incorporated into numerical software. The results suggest that these predictive methods are capable of capturing the measured behavior with reasonable agreement
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Comparison of direct and indirect measured soil-water characteristic curves for a silty sand
No full textIt is time consuming and needs sophisticated testing apparatus to determine unsaturated soil properties such as hydraulic conductivity and shear strength. Therefore, engineers hesitate to use unsaturated soil properties in economical geotechnical problem solving. To promote the use of unsaturated soil properties in geotechnical engineering designs, numbers of methods have been developed to estimate/predict unsaturated soil properties. The Soil-water characteristic curve (SWCC) defines the relationship between the soil suction and water content. During past few decades, different measuring and estimation/prediction methods have been developed by researchers to ascertain SWCC of soils. Among them, direct and indirect methods are widely used to measure the SWCC of soil. Indirect methods such as axis-translation technique are commonly used in the laboratory to determine SWCC. It is important to understand how well the indirectly measured SWCC is related to actual soil-water retention properties of soil during drying and wetting process. Bridging that research gap, in this study, Soil water characteristic curve (SWCC) of sandy soil was measured using both indirect (Axis translation method using Tempe Pressure Cell) and direct methods. The direct measured SWCCs were obtained by subjecting the instrumented soil column and model embankment to wetting and drying cycles. When comparing SWCCs measured by direct and indirect methods, it was found that the indirect method provides a very close agreement with the outcomes of direct methods. This ensures that the SWCCs measured in the laboratory by using indirect methods can be used in Geotechnical Engineering practice
Variations on the Author
Get PDF“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
Get PDFWe 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
The July 2015 Debris flow in Barsem, Western Pamir (GBAO) Tajikistan: Description and causes
Get PDFTajikistan is a landlocked country in the Central Asia republics of the former Soviet Union. Tajikistan is prone to many natural disasters. Most commonly in Tajikistan, mudflows occur in the South and North parts of the country. The 2015 Barsem mudflow caused significant damage to the entire village, a territory of the Western Pamir Gorno-Badakhshan Autonomous Region (GBAO), Tajikistan; fortunately, no human casualties. The total volume of debris flow is about 4.9 million m3. Typically, precipitation above 15-20mm per day in arid areas causes mudflow. Accumulated water during the intensive melting of the glacier and snowfields was saturated with water by the moraine sediment blocking its paths (which served as a dam for the lake that formed). Several studies indicate that mudflow triggers excess pore pressure or liquefaction of the soil; consequently, sudden and high shear resistance losses eventually generate a mudflow [5][6]. Although mudflows and landslides occur annually, after the 2015 Barsem mudflow, it becomes clear that the intensity and frequency of new events are increasing. Consequently, the author strongly believes establishing and implementing an early warning system can be essential
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