1,721,138 research outputs found
On Modelling the Behaviour of Melanges
No full textGlacial tills and residual soils are two examples of heterogeneous soils or melanges, containing particles of widely disparate size. A constitutive model to describe their mechanical behaviour on the basis of a two-component mixture scheme is proposed. Results of compression tests, performed under triaxial and one-dimensional conditions on artificial melanges of gravel and kaolin in various proportions, are then used to verify the effectiveness of the mode
Mechanical behaviour of silty soils of the Venice lagoon as a function of their grading characteristics
Full text linkThe main feature of the shallowest quaternary basin of the worldwide known historic city of Venice, Italy and its surrounding lagoon is the presence, apparently without any regular trend in depth and site, of a predominant silt fraction. This is always combined with clay and/or sand, forming a chaotic and erratic interbedding of different sediments, whose mineralogy is however variable in a relatively narrow range due to a unique geological origin and a common depositional environment. After a brief description of the basic soil indexes of the Venice lagoon soil, the present study, based on a comprehensive geotechnical laboratory investigation, describes the range of variation of the most relevant time-independent geotechnical properties. Moreover, a new grain size index, combining the geometrical characteristics of the particle distribution, is introduced. It is shown that the soil response at large and very small strains can be related to this grain size index, that appears to be able include the influence of the soil grading on the description of the overall mechanical behavior
Some remarks on the behavior of Venetian silts
No full textThe behavior of the Venetian clayey silts has recently been studied at the Geotechnical Laboratory of the University of Padova through a series of triaxial tests carried out on a computer-controlled system equipped with local strain measurement devices. The results of this experimental investigation are presented and discussed in this paper paying particular attention to the mechanical response in the very-small and intermediate strain range
Influence of recent morphological evolution on the stability of two slopes in the Euganean Hills
No full textThe Euganean Hills rise isolated in the Venetian alluvial plain, covering an area of about 120 km2 and reaching an altitude of 600 above m.s.l. They are composed of sedimentary and eruptive rocks, the former composed by limestone and marl and the latter by basalts, ryolithes, trachytes and latites.
The marl and basalt formations are normally covered with layers of weathered clay materials. These colluvial materials, having sometimes thickness of several metres, show precarious equilibrium also on gently conformed slopes. Recent census of landslide movements singled out about 140 unstable areas, corresponding to about 4% of the total surface of the hills. The landslides are due to anthropic as well as natural causes.
Since about 2000 years, the morphology of the Euganean Hills has been intensively modified by several types of human activities, among which the most important is probably represented by open quarries of marls and trachytes. The former are generally excavated from the toe of the slopes whereas the latter from the volcanic outcrops. These excavations involve sharp variations of the profiles of the hills.
Terracing for agricultural purposes, construction of new roads, changes of river paths or of the surface drainage system also create alterations of the original profiles of the hills, but their effects on slope stability are probably of less importance with respect to intensive quarrying activity performed during the last decades.
The influence of human activity on the stability conditions of two landslides is presented and analyzed in the paper using both limit equilibrium and finite element method. These movements, due to sliding along slightly dipping surfaces (8°-10°), are located in the Southeastern Sector of the Euganean Hills and involve the colluvial covers resting above the marly deposits
Stabilizzazione di movimenti franosi con ancoraggi flottanti: il caso di frana Val Maso (Valli del Pasubio, Vicenza)
Full text linkLa nota presenta una tecnica per la stabilizzazione di movimenti franosi denominata “ancoraggio flottante” che è stata oggetto di studio e di sviluppo teorico e applicativo all’interno di un Dottorato di Ricerca a tema. La tecnica prevede l’installazione di ancoraggi passivi nel corpo di frana, cementati al terreno e con adeguata fondazione nel terreno stabile profondo, posizionati secondo una geometria discontinua senza una parete di rivestimento del versante, ma con la sola applicazione di una piastra di ridotte dimensioni collegata alla testa di ciascuna barra. Dopo una rapida presentazione della tecnica e di un semplice schema di dimensionamento, si presentano un’applicazione per la sistemazione della frana di Val Maso (Valli del Pasubio, Vicenza) e i risultati di 18 mesi di monitoraggio post intervento
Floating anchors for the stabilization of Cischele landslide in the Venetian Prealps
Full text linkDue to its weather-climatic, geological and geomorphological conformation, Italy is particularly subject to geo-hydrological hazard. Almost 500,000 landslides have been recorded in Italy in a total area of 21,182 km2, representing the 7% of the national territory (ISPRA, 2014). New alarms intensify during exceptional rainfalls: for instance, in the first days of November 2010, in the Alpine foothills in Vicenza province (North-Eastern Italy), more than 500 landslides alarms have been registered (Floris et al., 2012). Therefore, the research for innovative and cost-effective solutions for risk mitigation and landslide stabilization has great scientific and socio-economic relevance.
The paper deals with the main results of a research conducted for developing, both in theoretical and applied aspects, a new technique for the stabilization of landslides, called “floating anchor”. In particular, this paper focuses on the stabilization works and monitoring of a landslide located in the Cischele hamlet near Recoaro (Vicenza, Italy), in the Venetian Prealps, where an intervention with floating anchors have been set up
The shear strength behaviour of two peaty soils.
Full text linkThis paper presents experimental research concerning the shear behaviour of two type of Italian peats, one normally, the other over consolidated. Organic soils are characterized by very high compressibility and high fiber content; two features that give rise to several problems during laboratory tests. Under consideretions here are the effects of fiber and overconsolidation over friction angle and shear-strain behaviour. These are evaluated by means of undrained compression triaxial tests, with isotropic and anisotropic (Ko) consolidation being performed on natural and remolded samples. The experimental results are also analysed by means of a bilinear failure criterion based on soil-reinforcement interaction mechanisms
Un modello multifase per il calcolo dei cedimenti in depositi eterogenei.
No full textL’articolo illustra un nuovo modello costitutivo elastoviscoplastico per descrivere la compressione 1-D dei terreni di transizione, cioè di quei terreni, come le sabbie argillose, che possono essere idealmente immaginati come una miscela di due fasi solide mutuamente interagenti, rappresentate dalla frazione granulare e dalla matrice fine. Le equazioni che interpretano la mutua interazione tra le due fasi solide e il fluido interstiziale sono in grado di descrivere la risposta del terreno per tensioni variabili da pochi kPa fino a svariati MPa, in corrispondenza ai quali avviene la frantumazione delle particelle granulari. La validità del modello è stata accertata mediante la simulazione del comportamento in prove di compressione 1-D condotte sui terreni della laguna di Venezia, tipico esempio di deposito naturale di terreni di transizione. Oltre alla formulazione del modello, nell’articolo sono evidenziati gli aspetti legati alla calibrazione dei parametri e all’applicazione a situazioni in vera grandezza, discutendo vantaggi e limiti dell’approccio proposto nella simulazione del comportamento di opere che insistono sui depositi della laguna di Venezi
A two-phase model to describe the behaviour of saturated granular-cohesive soil mixtures
No full textParticle Image Velocimetry to measure displacements of a model sandy slope
No full textThis work deal with the use of a digital image correlation technique (Particle Image Velocimetry) to measure the displacement of a sandy slope. This method allow to recognize displacement with high spatial and temporal resolution and to easily detect shear band in the soil mass
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