1,720,988 research outputs found
Valutazione del danno da frana per l’analisi di vulnerabilità in un’area urbana del Subappennino Dauno
No full textLa valutazione del rischio da frana rappresenta un tema di crescente interesse a causa del condizionamento dei processi franosi sullo sviluppo socio-economico dei centri urbani e sulle possibilità di conservazione del patrimonio storico-culturale. In Italia, questo problema è particolarmente sentito per l’estensione delle aree interessate dai movimenti di massa, spesso responsabili di danni ricorrenti a strutture ed infrastrutture. Con riferimento alle frane a cinematica lenta, le valutazioni di rischio di tipo quantitativo riguardano aspetti prevalentemente connessi alla suscettibilità o, in alcuni casi, alla pericolosità, limitando invece gli studi sulla vulnerabilità strutturale ad analisi di natura pressoché qualitativa. Questo contributo intende indagare gli effetti dell’interazione tra una classe di frane a cinematica lenta, ovvero gli scorrimenti roto-traslativi profondi, ed il patrimonio costruito sovrastante. In particolare, si presentano i risultati dell’applicazione di una nuova procedura di valutazione del danno da frana di edifici ordinari, sviluppata come step operativo di una metodologia multilivello per l’analisi di vulnerabilità alla scala del centro urbano. L’applicazione al comune densamente urbanizzato di Pietramontercorvino (sub-Appennino dauno pugliese), in un’area di affioramento di formazioni Flyschoidi, disomogenee e meccanicamente scadenti, ha consentito la classificazione degli edifici danneggiati da cedimenti di fondazione attraverso l’assegnazione del relativo grado di danno al singolo edificio. I risultati delle analisi geomorfologiche, geotecniche e strutturali alla scala del centro abitato sono confluiti nella ‘carta geotecnica del danneggiamento da frana’, strumento di supporto per l’analisi di vulnerabilità e la valutazione del rischio da frana nell’area
The geo-hydro-mechanical properties of a turbiditic formation as internal factors of slope failure processes
No full textSimilar to many inner areas of Southern Europe, the Daunia Apennines are affected by widespread landsliding, often consisting of slow, deep-seated movements. Recurrent acceleration of these landslides causes damage to buildings and infrastructures, severely biasing the socio-economic development of the region. Most landslides in the area of study occur within clayey units of turbiditic flysch formations, often severely disturbed by tectonic thrust and previous landsliding. The Faeto Flysch (FAE) is one of the most widespread turbiditic formations in the Daunia Apennines and is representative of the tectonised geological formations involved in slope failure. This work, by examining the landslide processes occurring at four pilot sites, aims at connecting the observed mechanisms to the geo-hydro-mechanical setup of FAE in the slopes. It is found that the soil portion of FAE consists of highly plastic clays, resulting in low intrinsic shear strength, and hence controls the initiation and progression of failure in the slopes, as such representing an internal predisposing factor to landsliding. In addition, the presence of fractured rock strata confers a high permeability at the slope scale, with respect to that of the soil matrix. This results in severe piezometric levels in the slope, which represent another internal predisposing factor to failure, and in the ability to induce significant seasonal pore water pressure oscillations down to great depths, connected to rainfall infiltration, thus triggering the recurrent acceleration of the landslides
Effects of micro- to meso-features on the permeability of fissured clays
No full textThis paper discusses the relation of the coefficient of saturated permeability in a given direction, ki, with the void ratio, e, for fissured and unfissured clays, wherein ki characterises the hydraulics of the equivalent uniform porous model. The ki - e data for the fissured clays are compared with what is observed for unfissured clays, either natural or reconstituted. For each clay, the ki - e data result from laboratory investigation and are related to the fissuring identity of the clay, classified through a fissuring characterisation chart. Through this procedure, the study provides an initial rational insight of the variability of the ki - e law with both the micro- and the meso-scale clay features. Fissuring is shown to cause meso-scale non-uniformities of the flow patterns, which may cause a variation between the ki for steady-state seepage and that controlling transient seepage. In general, fissuring increases the clay permeability with respect to the same clay if unfissured and also with respect to the same clay when reconstituted. Also, the study sheds light on the difference between the ki - e law holding during compression and that during swelling for both unfissured and fissured clays, showing that such difference is more important for fissured clays
A microstructural insight into the compression behaviour of scaly clays
No full textScaly clays are intensely fissured clays with lens shaped elements of millimetre size and show a complex compression behaviour that poses challenges to the design and construction of geostructures (excavations, retaining diaphragms, and tunnels). Scaly clays show a Normal Compression Line (NCL) where plastic deformation accumulates as typically observed in non-scaly clays. Yet the response observed upon unloading and subsequent reloading is very peculiar, i) the unloading-reloading cycle is typically a close-loop with relatively large hysteresis; ii) the compressibility recorded at high OCR ratio of the unloading or reloading branches is close to the NCL compressibility. This paper presents a microstructural study on an Italian scaly clay where SEM observations are integrated with Mercury Intrusion Porosimetry (MIP) analyses and X-ray Computed Tomography (XCT) images. The mechanism associated with the closing of inter-scale porosity and the generation of new intra-scale porosity was identified as the process responsible for the plastic deformation. Experimental observation of reconstituted clay showed a "quasi-reversible" behaviour upon loading and unloading and a pore size distribution characterized only by interparticle porosity. The observation that unloading and reloading curves are parallel in natural and reconstituted clays, led to postulate that the interparticle porosity is controlling the elastic response
Landslide damage assessment at the intermediate to small scale
No full textThis paper presents an original methodology that has been developed for the landslide damage assessment of either masonry or reinforced concrete ordinary buildings at the intermediate to small scale. After a brief introduction of the Load Path Method used for the analysis of the crack patterns, new survey damage forms are introduced. The forms are completed when a damage grade is assigned to each building within the region under study. Moreover, the analysis of the crack patterns makes it possible to select those buildings that are likely damaged by foundation settlements in order to create a landslide damage geotechnical chart. This chart includes the geomorphological map of the town under study, the damage grade of the buildings and the direction of the possible settlements. The application of the methodology to a territorial cell from the south of Italy is also reported
Geotechnical investigation of submarine sediments for the environmental characterisation of a contaminated site.
No full text
Deterministic landslide hazard assessment at regional scale
No full textThe paper presents a new methodology for the deterministic assessment of landslide hazard at the regional scale in geologically complex chain areas. The methodology entails site specific geo-mechanical studies, as background of any hazard prediction application, and the creation of a Regional Landslide Manual portraying the geo-mechanical knowledge about the slope conditions across the region. The search in the regional manual of the landslide mechanisms which may correspond to the combination of landslide factors recorded at the local scale results in the hazard prediction. The testing of the methodology in the Daunia Apennines is discussed. © 2010 ASCE
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