1,720,992 research outputs found
Structure degradation and changes in the mechanical behaviour of a stiff clay due to weathering
No full textThe paper discusses the results of research into the causes of weathering of stiff Pleistocene clays located in the Montemesola Basin (TA, Italy), and on the effects of weathering on the flay's mechanical behaviour, The weathered clays are yellow-brown and overlie the original grey clays in the whole basin. The liquidity indexes of both the yellow and the grey clays, their fabric, as observed by means of scanning electron microscopy, as well as the yellow clay oxidation features suggest that drying has been the main weathering process in the basin. This is confirmed by the results of drying-wetting cycle tests carried out in the laboratory on undisturbed clay samples, which show the drying-wetting cycles to produce changes in the grey clay similar to those present irt situ due to weathering. Results of oedometer, stress path and triaxial tests show that weathering has caused a degradation of the clay bonding and an associated reduction in the size of the clay state boundary surface. Both one-dimensional and isotropic compression data and the shear data indicate that the effects of weathering on the mechanics of the clay may be established according to the decrease in the clay stress sensitivity. Weathering also causes a decrease in the normalised shear stiffness, as observed by means of bender element tests, which is also related to a decrease in the stress sensitivity
Microstructural Changes in Clays Generated by Compression Explored by Means of SEM and Image Processing
Full text linkAbstractA study on the microstructure of an illitic marine clay is carried out through a thorough investigation of the clay origin, composition and current microstructure. The clay fabric is investigated by means of scanning electron microscopy (SEM) and statistically analysed by means of image processing. The nature and strength of the clay bonding are probed by means of direct chemical micro-analyses and on purpose strain paths. The same investigation is carried out both on the natural and on the reconstituted clay, at the initial state and after one-dimensional compression to medium and large pressures
Influence of roots on the hydro-mechanical performance of a drainage geocomposite
No full textGeosynthetics are increasingly used in geotechnical works in association with vegetation, whose function has been typically considered as an improvement for the works themselves, especially due to the mechanical and hydraulic effects the root system provides. Within this context, the paper presents an experimental study performed to evaluate the long-term performance of geosynthetics, specifically drainage geocomposites, exposed to the influence of roots. Two species of plant were selected for their fast-growing and pervasive roots, Vetiver and Bamboo, and planted in a thin layer of growing medium, which buried the geosynthetic specimens. After a period of plant growth, the specimens affected by roots ("rooted specimens") were exhumed, and submitted to tensile and drainage capacity laboratory tests, to determine their mechanical and hydraulic behaviour. The laboratory test results were compared with those obtained on virgin specimens of drainage geocomposite, under undisturbed conditions ("reference specimens"). The results show a decrease in drainage capacity for rooted specimens, more pronounced in the case of the highest density of roots into the drainage core. Concerning the tensile behaviour, no significant variations emerged in rooted specimens, although a slight increase in tensile strength, together with a modest decrease in elongation at maximum load, could be observed
“In situ and laboratory investigation of the saturated hydraulic conductivity of a clayey soil cover when bare or vegetated”
No full textPreliminary assessment of the correlation between three-dimensional topography and lining forces induced by earthquakes on shallow tunnels
No full textThe Impact of a Wildfire on a Vegetated Topsoil: Field Monitoring and Numerical Modeling
No full textWildfires are generally believed to be detrimental to slope stability by damaging vegetation and altering the thermo-hydro-mechanical properties of soil due to thermal stress and burning. However, the extent to which wildfires may impact on state of the vegetation and soil state is still an open issue, as it depends on several factors such as the fire intensity and persistence, as well as the soil and vegetation state and type. This research focused on a wildfire event that was monitored and back-analyzed using thermal finite element modeling by using Plaxis 2D to understand the impact on the soil post-wildfire state. The study was conducted at a field test site located at the toe area of the Pisciolo hillslope, where selected vegetation had been seeded and farmed to investigate the soil–vegetation–-atmosphere (SVA) interaction. The test site was the location of a wildfire in September 2023, which burnt most of the vegetation. The results show that the heat flux due to the wildfire is in the range between 100 and 150 kW/m2 with a duration of 5–10 min. Field monitoring revealed that significant wildfire-induced temperature variations were confined to the near-surface soil layer, up to a depth of 20 cm of soil, with only slight changes in the soil properties
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
Non-linear site effects in areas characterised by a complex topography: an Italian case study
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