1,721,009 research outputs found
LANDTRAIN: VERSION 1.
No full textThis is a code written in R language devoted to identify 8 possible rainfall events that are likely to be responsible for one shallow landslide. Accordingly, the input file contains a portion of the rainfall measures related to the nearest rain-gauge to the landslide point. The code enables non expert users to calculate the following values: Duration of 8 rainfall events, related 8 Cumulated raifalls and Intensities responsible for the shallow landslide under study
Reliability approach to the side resistance of piles by means of the total stress analysis (alfa method)
No full textThe evaluation of the pile–soil adhesion plays a fundamental role in the estimation of the side resistance for total stress analysis. Over the years, researchers have presented proposals for adhesion factor formulations even though only
a few of them have shown a certain agreement in numerical and (or) methodological terms. Hence, several real-size experimental analyses have improved the understanding of the pile–soil adhesion phenomenon and mechanism. Nevertheless,
the undrained shear strength (cu) values depend on the experimental technique employed. Such results force engineers to make a difficult choice among various formulations. A reliability analysis is performed in this paper to take into consideration the variations in formulations and values of the side resistance of bored piles in clayey soils. This study involves piles having different lengths and diameters, which are supposed to be bored in Matera clays. Such soil is characterized by means of laboratory investigation campaign, and its mechanical and stochastic main features are reported here. Values of reliability index are calculated by means of the first-order reliability method
Relevant features of the valley seismic response: the case study of Tuscan Northern Apennine sector
No full textThe so called "valley effect" relates to the typical seismic response of basin shaped bedrock filled by quaternary sediments. It is an aspect of the renown "local seismic
effect" that shall be taken into account when dealing with microzoning studies. Several experimental surveys and numerical simulations performed worldwide over the last 40
years, confirmed that valley responses under seismic excitations show common features in various geological contexts as far as the sedimentary valleys (e.g. alluvial
and lacustrine plains), the intermountain valleys (e.g. alpine valleys) and graben shaped basins. Such features mainly depend on the basin geometry, referred to as the
shape ratio SR, and the sediment and basin impedance contrast IC. Although
researchers agree on the prominent role of local seismic effects for interpreting erratic
damages caused by seismic shaking in urbanized areas, no fully shared strategies
have been identified for taking into account valley effect within microzoning studies. In
this paper, a numerical simulations on three models of trapezoidal shaped basins have
been performed. These valley models relate to sediments and basins detected within
the Tuscany Region territory during the VEL project. Results, in terms of the
amplification index FA have been provided. Three "valley effect charts" for various SR
and IC values have been propose for taking into account the local seismic effects due
to the basin amplifications within macrozonation maps
Capitolo 11. Microzonazione sismica di livello 3
No full textIl lavoro presenta i risultati di studi numerici finalizzati alla microzonazione sismica di livello 3 nell'ambito del territorio regionale toscano
Landslide mitigation methods
No full textIl capitolo illustra le metodologie classiche per la sistemazione di un pendio in ottica di riduzione della suscettibilità a franamento, condotta mediante drenaggi, miglioramenti di resistenza meccanica dei terreni e riprofilatura del pendio. Si considerano sia pendii in terra che in roccia
Reliability analysis of slopes
No full textIn this paper has been described a new procedure by which the characteristic limit state line of a geometrically known slope can be calculated. This approach is based on an intuition, applied to a deterministic evaluation of slope stability to look for a slope characteristic "failure curve". Subsequently, concerning probability perspective, has been considered Low's interpreting the reliability index. Linking prior studies together and to the Characteristic Resistance Envelope Procedure an Overall Approach has been developed. A simple computed case is included in order to show computing potentialities of this new approach
Affidabilità dei pilastri di roccia tenera in cave sotterranee
No full textLe rocce tenere sono, in genere, estratte in cave a cielo aperto. Specie nel passato, però, quando la roccia si
rinveniva a profondità di un decina di metri e la copertura era costituita da materiale diverso, come ad
esempio l’argilla, la coltivazione in sotterraneo poteva risultare conveniente se confrontata con l’alternativa di
uno scavo a fossa previa eliminazione del materiale di copertura. In tal modo, si assicurava altresì la
continuazione dell’utilizzo della superficie del terreno in maniera pressoché indisturbata. Esempi di
coltivazioni di questo genere sono piuttosto diffusi. Esse utilizzano la tecnica di estrarre il materiale lasciando
dei pilastri di dimensioni opportune a sostegno della volta. Molte di queste coltivazioni sono attualmente
abbandonate e spesso si riscontrano dei veri e propri collassi dei pilastri che, data la profondità non eccessiva
della zona soggetta a coltivazione danno luogo a dei veri e propri fenomeni di rapida subsidenza della
superficie del suolo. Tale circostanza si è verificata in Puglia più volte ed in particolare a Canosa, Mottola e
Cutrofiano. In tali casi l’analisi di stabilità dei singoli pilastri viene generalmente svolta considerando come
azione, il carico verticale, indotto dai terreni sovrastanti la volta, relativo ad un’area di influenza per il singolo
pilastro opportunamente determinata per via geometrica, mentre la resistenza è valutata conoscendo la
resistenza a compressione semplice di provini della roccia e considerando le caratteristiche geometriche dei
pilastri. Numerose sono le relazioni in tal senso disponibili in letteratura che, nel presente lavoro, vengono
presentate. Sulla base di quanto precedentemente detto, viene esaminato in dettaglio il caso della cava di
Mottola. La roccia in questione può essere classificata come calcarenite, localmente calcirudite, di colore da
bianco a giallino. Tali rocce sono biospariti a struttura prevalentemente grainstone e secondariamente
packstone-grainstone. I grani bioclastici carbonatici derivano dalla frammentazione sia di macro sia di
microfossili; secondariamente si riscontra la presenza di grani di quarzo, feldspati, ossidi di ferro e glauconite.
Dal punto di vista fisico-meccanico tale roccia può essere classificata come “roccia tenera”. La cava
sotterranea di Mottola, in analogia con altre cave sotterranee presenti in vari paesi ed attualmente utilizzate
anche per scopi turistici, è organizzata a camere e pilastri dei quali sono state accuratamente misurate le
dimensioni ed accertate le forme che solitamente non sono regolari. Conseguentemente è stato possibile, sulla
base di un’analisi statistica svolta sulla base dei dati geometrici e meccanici (per questi ultimi comprendendo
anche dati di letteratura), effettuare una stima dell’affidabilità della stabilità dell’insieme dei pilastri in cava,
in relazione alla probabilità di collasso degli stess
Random field theory to interpret the spatial variability of lacustrine soils
No full textThe mechanical characterisation of heterogeneous soils, such as alluvial deposits, is
commonly performed through a deterministic approach. This latter consists on applying
the engineering judgment to choose a mean trend from continuous vertical readings of in
field investigations (e.g. Cone Penetration Tests e CPTs) or discontinuous ones as Standard
Penetration Tests (SPTs). Conversely, in order to take into account the spatial variability of
mechanical measurements of the soil the spatial standard deviation, the scale of fluctuation and the autocorrelation function have to be calculated. This latter approach follows
the stochastic field theory and it can be fruitfully applied to all those soil formations that
are inherently heterogeneous. In this paper, theoretical bases of this approach has been
briefly described and a practical application to lacustrine soil deposits at Popoli site located
in Abruzzi Region (Italy) are presented. The methods introduced are not straightforward
but they provide information that can be used to improve both the reliability of the
geotechnical design and the efficiency of the soil use depending on the investigated depths
and the measurement intervals
Regional rainfall threshold maps drawn through multivariate geostatistical techniques for shallow landslide hazard zonation
No full textThe Empirical Rainfall Thresholds (ERTs) for shallow landslide initiation are commonly devised worldwide mostly to be implementedwithin landslide early warning systems. Nonetheless, since the pioneeringworks on ERTs in the 1980s, only meteorological variables - that are cumulated E or intensity I and duration D values of rainfalls that are likely to trigger landslides - have been used to predict landslide occurrence, even though they are characterized by a large uncertainty. Over time, many efforts have been devoted to constrain ERT to geo-morphological characters of the landslide locations but, since nowadays, they did not get to a sound newmethod to derive ERT and strengthen its ability to forecast future rainfall-induced landslide. In this study, local geo-morphological characters have been taken into account by means of the co-kriging technique to constrain the E and D mean values of a regional ERT and their confidence intervals. The study area, where the proposed method was trained, is the hilly side of the Abruzzo region (Italy). Here, 62 shallow landslides have been analyzed in the time span of 2013–2017 by collecting 62 (D,E) pairs related to the rainfalls that were likely to trigger them. The relevant geo-morphological features for the considered territory have been selected through the principal component analysis. Then, the Multi-Collocated Co-Kriging technique, through ISATIS Geovariances software, has been applied to derive the spatial variability structures of E and D values conditioned by the selected geo-morphological parameters. Therefore, threshold values of E and D and their confidence intervals have been calculated generating a new shape of regional ERT, consisting of maps of continuous estimated threshold values of (D,E) and confidence interval values suitable for being used in early warning systems for shallow landslide initiation
Seismically induced slope instability maps validated at an urban scale by site numerical simulations
No full textMaps of seismically induced instability at the urban scale can be drawn by means of geographic information
system (GIS) tools that integrate different information layers such as (1) a landslide inventory; (2) a digital
elevation model (DEM); (3) geo-hydro-mechanical site characterization, and (4) measured peaks or integral
parameters at seismic stations. These maps are used to guide planning activities and emergency actions, but their main limitation is typically the lack of reliable analyses or calibrations. In this study, a possible method is proposed to control and increase the overall reliability of an hazard scenario map of earthquake-induced slope instability. The procedure can be summarized in the following steps: (1) GIS tools are used to describe the spatial distribution of the hydro-mechanical properties of the surface lithologies; (2) seismically induced instability maps of permanent displacements are drawn from the preceding information layers combined with seismic parameters spatially propagated by means of spatial interpolation tools; (3) point dynamic and stability numerical analyses are carried out by means of a commercial finite element method (FEM) code
(e.g., Geostudio2004) to calculate permanent displacement by the Newmark’s method along representative cross-sections. The numerical analyses are used to calculate a ‘‘depth factor’’, which can be considered as the contribution of the seismic local amplification to the surface calculations addressed by GIS tools. The ratio between the results drawn from the two approaches (GIS-based and FEM-based implementing Newmark’s method) can be assumed as a scale factor related to the in-depth sitespecific geo-lithotechnical characters to be addeded to GIS maps
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