1,721,007 research outputs found
Experimental Methodologies for the Shear Tests on Soils Reinforced with Roots
No full textExperimental Methodologies for the Shear Tests on Soils Reinforced with Roots, First international conference of soil and roots engineering relationship (LANDCON1005), Ardebil Province, Iran, 24-26 May 201
Root reinforcement and slope bioengineering stabilization by Spanish Broom (Spartium junceum L.)
No full textThe present paper deals with the root system's characteristics of Spanish Broom (Spartium junceum L.), a species whose capacity for adaptating and resisting to drought is worth investigating. In particular, the aims of the study were 1) to investigate the plant's bio-mechanical aspects and 2) to verify whether root reinforcement and the field rooting ability of stem cuttings enhance its potential for use in slope stabilization and soil bio-engineering techniques, particularly in the Mediterranean areas. Single root specimens were sampled and tested for tensile strength, obtaining classic tensile strength-diameter relationships. Analysis were performed on the root systems in order to assess root density distribution. The Root Area Ratio (RAR) was analyzed by taking both direct and indirect measurements, the latter relying on image processing. The data obtained were used to analyze the stability of an artificial slope (landfill) and the root reinforcement. The measurement and calculation of mean root number, mean root diameter, RAR, root cohesion and Factor of safety are presented in order to distinguish the effect of plant origin and propagation. Furthermore, tests were performed to assess the possibility of agamic propagation (survival rate of root-ball endowed plants, rooting from stem cuttings). These tests confirmed that agamic propagation is difficult, even though roots were produced from some buried stems, and for practical purposes it has been ruled out. Our results show that Spanish Broom has good biomechanical characteristics with regard to slope stabilization, even in critical pedo climatic conditions and where inclinations are quite steep, and it is effective on soil depths up to about 50 cm, in agreement with other studies on Mediterranean species. It is effective in slope stabilization, but less suitable for soil bio-engineering or for triggering natural plant succession
Terraced landscapes: From an old best practice to a potential hazard for soil degradation due to land abandonment
No full textAmong the most evident landscape signatures of the human fingerprint, the terraces related to agricultural activities are of great importance. This technique is widely used in various parts of the world under various environmental conditions. In some areas, terraced landscapes can be considered a historical heritage and a cultural ecosystem service to be adequately preserved. However, terraced landscapes subject to abandonment can progressively increase gully erosion and cause terrace failure. Partly because of changes in societal perspective and migration towards metropolitan areas, some countries have been affected by serious and wide abandonment of agricultural lands in recent decades. This review aims to discuss the current state of agricultural terraced landscapes, underlining critical issues and likely solutions. The paper is structured in three main sections. The introduction provides an overview of the available literature on terraced landscapes and their critical issues. The second section presents three case studies: the first is located in the so-called Cinque Terre area (Liguria, Northern Italy), the second is placed in the Chianti Classico area (Tuscany, Central Italy), and the third refers to the renowned Amalfi Coast (Salerno, Southern Italy). The last section of the review relates to likely solutions (non-structural and structural management) and future challenges (use of high-resolution topography derived by lidar) for suitable management of such environments
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
Metodologie sperimentali per l’esecuzione di provedi taglio diretto su terre rinforzate con radiciExperimental methodologies for the direct shear testson soils reinforced by roots
No full textRoot apparatus profoundly modify the hydrological and geotechnical characteristics of the soil, making it less inclined
to collapse when under shear stress. During the last years many authors carried out different researches in the attempt
to scientifically establish the actual role of vegetation on the slopes and at which extent. In this sense, models have
been developed capable of foreseeing potential risks. These models are based on assumptions which are empirical
or have many experimental variables, tweaked with simulations, both in situ and in the laboratory, using plants
or artificial fibres of different nature and shear apparatus built on purpose.
The experimental tests proposed in this paper have been carried out following the direct shear test, according
to the standard defined by Casagrande, and they examine in a small scale the behaviour of rooted soil samples.
For the tests we used Castanea sativa M. and Robinia pseudoacacia L. roots. The test conditions are deliberately and
necessarily simplified, carried out on recreated test pieces, using two different methods developed during the
experiments, using a variable number of roots. The interesting aspect of this kind of test, is the possibility to underline
the behaviour of the soil until its failure (but not roots failure) occurs. At the same time we carried out tensile tests
on roots of the same species.
Besides the laboratory tests, in field tests were carried out with the Bore-hole Shear Test (BST), with the hypothesis
of the same experimental conditions of the laboratory.
Results were compared to the most recent models for the calculation of the additional cohesion and also the relation
between roots activation strength and the resistance to failure was analysed. The results obtained with the proposed
methods are coherent with the expected results, and they show an increase of the apparent cohesion and not significant
variations of the angle of internal friction. Analogously, the data in situ show that the soil shear strength is positively
modified by the increase of the RAR, which is in inverse proportion to the depth. The use of the Bore-hole shear test
deserves to be deepened, in order to know the actual efficacy of this tool in perceiving the soil root density
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
Quantifying the role of vegetation in slope stability: A case study in Tuscany (Italy)
No full textVegetation significantly affects hillslope hydrological and mechanical properties related to shallow land-
slide triggering. In view of the complexity of soil plant hydrological interactions, the quantification of root
mechanical reinforcement remains a challenge. Herein we present a back analysis of mechanical stability
criteria related to a well-characterized vegetated shallow landslide in Italy, focusing on the quantification
of lateral and basal root reinforcement. Lateral root reinforcement is included in slope stability estimates
by adding a stabilizing force proportional to the scarp surface and root distribution. This stabilizing force is
added to the force balance equation for the infinite slope model for different landslide shapes and dimen-
sions. To quantify root reinforcement, we use the Wu model and the fiber bundle model (WM and FBM,
respectively). Implementation of the latter model allows the quantification of the stress–strain behaviour
of a bundle of roots for different root distributions and mechanical properties. Results of these models
are compared highlighting key differences between the two approaches. Calculations using the FBM can
explain the overestimation of lateral root reinforcement using WM and the commonly observed overes-
timation in the factor of safety. The model also quantifies the displacement-dependent behaviour of root
reinforcement on vegetated slopes. Lateral root reinforcement can strongly influence the stability of slopes
up to a certain area (1000–2000 m 2 ). The magnitude of this stabilizing effect depends on parameters such
as inclination, soil mechanical properties, and root distribution.
Ecological Engineering (2010)
Volume: 36, Issue: 3, Publisher: Elsevier B.V., Pages: 285-291
ISSN: 09258574
DOI: 10.1016/j.ecoleng.2009.06.01
Soil-root mechanical interactions within bundles of roots
No full textSoil-root mechanical interactions within bundles of roots, Geophysical Research Abstracts, EGU2010-12591, 2-7 maggio 2010, Vienna
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