1,721,025 research outputs found
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
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
Indagini sperimentali sulla resistenza degli apparati radicali
No full textLa presente memoria è relativa alle misure di resistenza a trazione di radici condotte recentemente presso la sezione Idronomia del Dipartimento Ingegneria Agraria Forestale dell’Università di Firenze.
Le specie studiate sono Spartium junceum e Robinia pseudoacacia, tipiche dell’ambiente mediterraneo, per il loro utilizzo in interventi di sistemazione idraulico forestale. Si illustrano le procedure di campionamento, scavo, prelievo non distruttivo e conservazione). Sono descritte la strumentazione messa a punto presso il Laboratorio di Tecnologia del Legno del Dipartimento di Scienze e Tecnologie Ambientali Forestali dell’Università di Firenze e le modalità di prova per le misure del carico di rottura delle radici evidenziandone le caratteristiche significative, in particolare relativamente agli ancoraggi dei campioni ed alla velocità di misura.
Sono presentate le curve resistenza a trazione in funzione del diametro ricavate dalle prove condotte
, 28(2), 553–565
No full textInappropriate forest management degrades the quality of soil resources. Soil erosion, for instance, leads to decreased soil fertility and landscape quality. Coppice-wood management includes risk factors for soil erosion due to the partial and temporary lack of soil cover, and this review highlights the importance of considering both an adequate methodology and objective interpretation of findings. This critical review was carried out due to the substantial deficiencies in the research design and methodology, analysis and interpretation of data, and conclusions in the paper that are not supported by their findings. In this paper, we provide a different interpretation of their data, which reveals absence of substantial risk of soil erosion, even in the short period after coppicing when the soil is most exposed. We aim to provide a clearer context for readers about the impact of coppice management in Quercus ilex stands in the south of Sardinia
Advances in root reinforcement experiments
No full textRoot reinforcement is considered in many situations an important effect of vegetation for slope stability. In the
past 20 years many studies analyzed root reinforcement in laboratory and field experiments, as well as through modeling frameworks. Nearby the important contribution of roots to shear strength, roots are recognized to impart stabilization also through lateral (parallel to slope) redistribution of forces under tension. Lateral root
reinforcement under tensile solicitations (such as in the upper part of a shallow landslide) was documented and
discussed by some studies. The most common method adopted to measure lateral root reinforcement are pullout
tests where roots (single or as bundle) are pulled out from a soil matrix. These conditions are indeed representative for the case where roots within the mass of a landslide slip out from the upper stable part of the slope (such in a tension crack). However, there is also the situation where roots anchored at the upper stable part of the slope slip
out from the sliding soil mass. In this last case it is difficult to quantify root reinforcement and no study discussed this mechanism so far. The main objective of this study is to quantify the contribution of roots considering the two
presented cases of lateral root reinforcement discussed above - roots slipping out from stable soil profile or sliding soil matrix from anchored roots-, and discuss the implication of the results for slope stability modeling. We carried out a series of laboratory experiments for both roots pullout and soil sliding mechanisms using a tilting
box with a bundle of 15 roots. Both Douglas (Pseudotsuga menziesii) roots and soil were collected from the study area in Sardinia (Italy), and reconstructed in laboratory, filling the root and soil layer by layer up to 0.4 meter thickness. The results show that the ratio between pullout force and force transferred to the root during soil sliding range
from 0.5 to 1. This results indicate that measured pullout force always overestimate the contribution of lateral root reinforcement activated in situations where soil slide from anchored roots. That result implies a comparison and calibration of the models used for the calculation of root reinforcement
Hydrological, mechanical and spatial characterisation of root reinforcement in Mediterranean shrub vegetated slopes
No full text[182] Dani A., Giadrossich F., Preti F., Schwarz M., 2008, Hydrological, mechanical and spatial characterisation of root reinforcement in Mediterranean shrub vegetated slopes, EGU 2008, Wie
Comparing the hydraulic properties of forested and grassed soils on an experimental hillslope in a Mediterranean environment
No full textThis experimental research compares the physical and hydraulic properties of two adjacent soils, one covered with a native forest of Mediterranean maquis, and the other with spontaneous grass. The latter replaced the previous natural forest. The aim is to quantify the significant differences in the soil properties caused by the removal of the natural vegetation. Although the soil texture was similar in the different land uses, the soil under the forest had a higher organic matter content, a lower apparent density and a higher water content at saturation than the grassed soil. The
analysis of the water retention characteristics indicated that the retained water content of the forest soil exceeded that of the grassed soil in the range from saturation to -50 cm of water tension. This suggests that changing the land use altered the soil pore structure within this range. The hydraulic conductivity of the forest soil exceeded that of the grassed soil at water tensions of -10, -5 and -3 cm. Conversely the hydraulic conductivity of the grassed soil was similar to that of the forest soil at -1 cm of water tension and at saturation. This result was probably due to the hydraulic activation of the desiccation cracks in the grassed soil. This increased the amount of infiltrated water in saturated and near-saturated soil conditions. This work shows that changes in land use have an unfavorable impact on the physical and hydraulic properties of the soil. Soil covered with grass is more vulnerability to water erosion than that under forest, and there is likely to be general worsening of flow regimes
Investigation on the soil reinforcement of root networks
No full textInvestigation on the soil reinforcement of root networks. International Conference: Triggering of Rapid Mass Movements in Steep Terrains - Mechanisms and Risks (TRAMM), April, 11-16 2010, Monte Verità, Ascona, Switzerlan
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
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