1,720,993 research outputs found
Lifetime assessment of exposed PVC-P geomembranes installed on Italian dams
No full textThe aim of this paper is to study the performance of plasticised polyvinyl chloride (PVC) geomembranes used in the rehabilitation of concrete and masonry dams. In such applications, the geomembranes are left exposed on the upstream face, without external protection, to environmental factors and weather conditions, especially to UV rays. Evaluation of the performance and the lifetime assessment of the geomembranes is very important from a managerial point of view. Therefore, the results from a 25-year ongoing study on the long-term performance of PVC-P geomembranes installed on the upstream face of Italian dams are presented. The sampled geomembranes have been subjected to physical and mechanical tests and the results interpreted with reference to the variation of plasticiser, tensile characteristics, foldability at low temperatures, volumic mass and water vapour permeability. In the analysed samples, the loss of plasticiser range from 14.83% to 21.86%. This decrease in plasticiser content resulted in slightly higher modulus and tensile strength. The functionality of the geomembranes was not affected, as evaluated also by on site inspection. On the basis of the experimental results, lifetime predictions of the exposed geomembranes using the function of the loss of plasticiser were made
Comportamento nel tempo di geomembrane utilizzate per il ripristino del paramento di monte in dighe di calcestruzzo e muratura
No full textLong-time behavior of exposed geomembranes used for the upstream face rehabilitation of concrete and masonry dams
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Environmental aspects in geosynthetic-soil reinforcement structures: The role of vegetation
No full textWherever ecological solutions are desirable, soil bioengineering methods in slope stabilisation and soil erosion control are becoming more widely used. In this context, the design and application of geosynthetic-reinforced soil structures with vegetated face steep slopes has long emphasized aspects of environmental impact. In engineering practice, vegetation is increasingly used to protect artifi cial and natural slopes against shallow landslides and for surfi cial erosion control. The potential use of protection forests to combat shallow slope instabilities is becoming increasingly important, especially in the light of recent landslides and debris/mud fl ows in certain regions, triggered by rainfalls with increased intensity. The presence of vegetation contributes to maintaining slope stability and to reducingsurface soil erosion, both by reinforcing soil shear resistance and influencing the hydro-geologic conditions of soil. Methods to measure and predict the effects of vegetation on mass-wasting processes have become of particular interest to both the academic and engineering communities. The roots of plants are anchored into the soil to support the above-ground parts of vegetation, thereby creating a reinforced soil matrix in which stress is transferred from the soil to the roots, increasing the overall strength of the matrix. The strength of rooted soil is, therefore, due to a combination of soil strength, root strength, and the strength of the bonds between the soil and roots. Vegetation influences slope stability and the erosion process with both mechanical and hydrological effects. In particular, the mechanical effects of vegetation (increase in soil shear strength) related to soil stabilisation will be described. Based on the analysis of available literature, the aim of this work is to present the specifi c role of vegetation in soil reinforcement applications through the analysis of fi eld investigation, experimental tests carried out on roots and on roots-soil systems and analytical and theoretical modelling. Due to lack of space, erosion applications will be not considered in this paper. The use of vegetation in works of civil engineering and landscaping has grown in importance, but specifi c design standards are still under discussion for the use of vegetation in slope stabilization. Therefore, the design and management of stabilization systems using plants require an accurate knowledge about the quantitative reinforcing root effects on soil strength
Geosynthetic Engineering and Vegetation Growth in Soil Reinforcement Applications
No full textIn Italy, since early times, the environmental aspects have always been a key issue on the design and the application. Consequently, the geosynthetic reinforced soil structures consist of vegetated face steep slopes. Furthermore, the use of vegetation has also been recognized and incorporated in engineering practice for erosion control and for stabilization of shallow slopes. Vegetation influences slope stability and erosion process by both mechanical effects and hydrological effects. In particular, in the paper, the mechanical effects of vegetation related to soil stabilization will be described. The purpose of this paper is to present the specific role of vegetation in soil reinforcement applications, by means of the analysis of the available literature on the (i) factors affecting root reinforcement of soil, (ii) experimental tests carried out on roots and on roots-soil system, and (iii) analytical and theoretical models. The erosion applications will not treated in this paper. The use of vegetation in civil engineering and landscape works has grown in importance, even if the specific design standard concerning the use of vegetation for slope stabilization is still under discussion. Therefore, design and management of stabilization systems by plants require an accurate knowledge about the quantitative reinforcing root effects on soil strength
I geotessili con funzione di filtro a contatto con terreni granulari: criteri e parametri di progetto
No full textL’uso dei geotessili con funzione di filtro è sempre più diffuso nelle applicazioni di ingegneria geotecnica ed ambientale. In tutte queste applicazioni le principali funzioni del filtro sono quelle di prevenire l’erosione interna del terreno di base e di permettere il libero drenaggio del fluido filtrante.
La progettazione di un geotessile con funzione di filtro richiede la conoscenza dell’interazione, dovuta al moto di filtrazione, tra terreno di base ed il filtro; molto complessa a causa del gran numero di parametri in essa coinvolti.
Nell’articolo vengono rivisti criticamente e validati i principali criteri di progetto (di ritenzione e di permeabilità) dei geotessili con funzione di filtro e viene, inoltre, illustrata l’influenza dei principali parametri che ne influenzano il comportamento filtrante al contatto con terreni di base granulari
Performance and durability aspects related to the use of geosynthetics in capping systems.
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