1,720,983 research outputs found
Mechanical characterization of the Sergnano reservoir by ultrasonic wave velocity measurements
No full textApplicazione di modelli cinematici per lo studio di frane di crollo in media Val San Giacomo (SO)
No full textLe frane di crollo sono comunemente diffuse in tutte le regioni di montagna e, a causa delle elevate velocità con cui si verificano, non è possibile installare strumentazioni né di monitoraggio né di allarme; questo comporta, in un territorio notevolmente antropizzato come quello italiano, notevoli rischi. Per questo motivo è estremamente importante riuscire a valutare la diffusione spaziale e l’intensità del fenomeno di caduta massi. Il presente lavoro ha lo scopo di applicare modelli cinematici che consentano lo studio dei fenomeni di crollo, attraverso un’analisi di sensitività, ponendo particolare attenzione sui parametri che maggiormente influenzano il risultato.Rockfalls are very common in all mountains areas, they are very rapid and then the installation of monitoring and warning equipment is not possible. Therefore great risks are implied, especially in an heavily urbanized territory, such as the Italian one. For this reason the assessments of spatial distribution and intensity of rockfall are extremely important. This paper deals on the application of kinematic models that allow rockfall study, through a sensitivity analysis, focusing on the parameters that most influence the outcome.Les éboulements dûs à des effondrements sont communément répandus dans toutes les régions de montagne et, à cause des vitesses élevées avec lesquelles ils se vérifient, il n'est pas possible d'installer des instrumentations ni de monitorage ni d'alarme; cela, dans un territoire notablement antropisé comme celui italien, entraîne des risques considérables. Pour cette raison, il est extrêmement important de parvenir à évaluer la diffusion dans l'espace et l'intensité du phénomène de la chute des rochers. Le travail ci-dessous a pour but d'appliquer des modèles cinématiques qui permettent l'étude des phénomènes d'effondrement, en effectuant une analyse de sensitivité, c'est-à-dire en portant une attention particulière aux paramètres qui ont une influence majeure sur le résultat
ROCKFALLS: IN SITU TEST, KINEMATIC SIMULATION AND MITIGATION MEASURES – SASSO FARINACCIO CASE STUDY
Full text linkThis research deals with the analysis of rockfall motion and the importance of kinematic
simulations as well as in situ tests in designing of protection measures.
The study area is a talus slope located in Northern Italy (Provence of Sondrio), where
rockfalls frequently occur. The positions and dimensions of fallen blocks were measured and
used in the calibration process, performed through the back-analysis approach. The calibrated
values of restitution coefficients were compared with those obtained from in situ tests, which
were carried out on the examined slope. Looking at the resulting rock fall hazard, the bidimensional
kinematic simulations were performed in order to individuate the most suitable
location and dimensions of mitigation measures
Mount Farinaccio rockfall : comparision between kinematic simulations and experimental field tests
Full text linkI fenomeni di caduta massi sono frequenti nelle aree alpine e, per mitigare i rischi che creano alla popolazione ed agli insediamenti umani, è indispensabile una corretta previsione delle possibili traiettorie e dei parametri cinematici del moto che i blocchi in incipienza di movimento assumerebbero qualora si staccassero dalla parete. Il presente contributo riguarda lo studio dettagliato del moto di caduta massi e della sua propagazione, ottenuto grazie alla realizzazione di prove sperimentali effettuate in Val Grosina (SO). I risultati della sperimentazione sono stati paragonati con quelli provenienti da simulazioni cinematiche precedentemente effettuate nell’area d’indagine, utilizzando differenti metodi, sia bidimensionali sia tridimensionali. In una prima serie di simulazioni i dati di input caratterizzanti il moto dei blocchi sono stati ipotizzati sulla base dei valori bibliografici, ottenuti in contesti geologici e geomorfologici simili a quello di indagine, mentre in una seconda serie tali valori sono stati stimati basandosi sulla posizione di arresto di alcuni blocchi crollati nell’area di studio nel 2010. Il confronto dei risultati ottenuti utilizzando i diversi approcci con quelli sperimentali, mostra che, per ottenere previsioni affidabili delle traiettorie dei blocchi e quindi mappe di pericolosità attendibili, è necessario effettuare un’accurata calibrazione dei parametri che caratterizzano il moto di caduta
Geomechanical surveys and geostatistical analyses in Valchiavenna (Italian Central Alps)
Full text linkThe present study concerns the forecast of geomechanical features in rock masses and how mechanical properties can be regarded as regionalized variables. It considers an area of about 200 km2, extended in the Italian Central Alps along the Valchiavenna Valley (SO) - San Giacomo and Bregaglia valleys - where different civil and mining works are present. The regional geological setting is related to the Pennidic Nappe arrangement, characterized by the emplacement of sub-horizontal gneissic bodies resulting from the Mesoalpine isoclinalic folding of crystalline basements (“Tambò” and “Suretta” Units) emplaced throw East and separated by metasedimentary cover units.
More than one hundred detailed structural and geomechanical field surveys, mainly located in San Giacomo Valley, were carried out in order to characterize the rock masses, in accordance with the I.S.R.M. suggested methods. The procedure allowed to identify the number of joint sets and their average orientations, supplying a quantitative description of the discontinuities in terms of spacing, persistence, roughness, aperture, filling, wall strength and weathering. From the collected data the rock mass quality indexes have been evaluated in each surveyed site.
Geostatistical methods have been applied to study the spatial distribution of the main rock masses characteristics, such as joint set orientation, fracture intensity and joint spacing, being the direct survey data local. Where no data are available the rock mass features have been estimated, the results obtained by kriging and conditional simulation techniques are presented
Why can rockfall normal restitution coefficient be higher than one?
Full text linkPerché nell’analisi del moto di caduta massi il coefficiente di
restituzione normale può essere maggiore di uno?
La modellazione del fenomeno di caduta massi è solitamente
svolta con l’ausilio di simulazioni cinematiche, che consentono di
calcolare le traiettorie dei blocchi potenzialmente instabili. Sui pendii
molto acclivi i risultati sono fortemente influenzati dal valore dei
coefficienti di restituzione, che quantificano la dissipazione di energia
durante l’impatto; poiché l’urto blocco-pendio è prevalentemente
anelastico, tali coefficienti dovrebbero sempre essere minori di uno.
Tuttavia evidenze sperimentali mostrano l’occorrenza di valori
superiori ad 1 nella direzione normale al pendio. La presente nota
analizza le relazioni che intercorrono tra i coefficienti di restituzione e
le caratteristiche del pendio, del blocco e del moto di caduta, partendo
da prove in situ svolte in Val Grosina (SO)
Spatial assessment of geomechanical rock mass properties by geostatistical analyses
No full textThe forecast of geomechanical rock mass properties can be an important goal in civil and mining engineering planning, especially when a wide area is involved. This work is a contribute in assessing how the geometrical and mechanical properties of the rock masses can be treated as regionalized variables. Indeed the present study deals with the reconstruction of main rock mass characteristics in an extended area, from punctual measurements of the rock mass features, through the use of different geostatistical techniques.
The research site is located in the Italian Central Alps, along the Chiavenna Valley (SO), which is composed by San Giacomo and Bregaglia valleys; it covers an area of about 200 km2.
The regional geological setting is related to the Pennidic Nappe arrangement, characterized by the emplacement of sub-horizontal gneissic bodies resulting from the Mesoalpine isoclinalic folding of crystalline basements (“Tambò” and “Suretta” Units) emplaced throw East and separated by metasedimentary cover units.
More than one hundred detailed structural and geomechanical field surveys, mainly located in San Giacomo Valley, unevenly distributed, were carried out in order to characterize the rock masses, in accordance with the I.S.R.M. suggested methods for the quantitative description of discontinuities in rock masses. The investigated lithologies belong to the “Tambò” Unit, to its meta-sedimentary cover and to the “Suretta” Unit. Geomechanical surveys allowed to identify the number of joint sets, their average orientations, spacing, persistence, roughness, aperture, presence and nature of filling, wall strength, weathering and moisture. From the collected data the rock mass quality indexes, such as the Rock Mass Rating and the Geological Strength Index, have been evaluated in each surveyed site.
The geomecanichal parameters derived from the measurement stations are local data, therefore in order to know how they are distributed outside the measurement points, in the entire study area, different geostatistical techniques were applied. First of all, the field data of the main rock mass features, such as the intercept of discontinuities, fracture intensity and aperture, were analyzed, and the main statistical parameters were calculated. Then a procedure of Gaussian anamorphosis was performed when necessary. Afterward the correlation structures of the defined rock mass features were investigated, at different scales, by means of a semivariogram analysis, taking into account the occurrence of anisotropic correlations. Both kriging method and conditional simulation techniques were applied to estimate the geomechanical variables. The best results, supported by the validation process, are obtained by conditional simulation method, which respect local extreme values, compared with kriging technique which tends to produce smoothened distributions
Analisi spaziale e previsionale delle proprietà geomeccaniche degli ammassi rocciosi della Valle San Giacomo (SO), mediante tecniche geostatistiche
No full textLe proprietà geomeccaniche degli ammassi rocciosi dipendono da caratteri geologico-strutturali a scale differenti, regionali e locali. Il presente studio riguarda la variabilità spaziale del grado di fratturazione degli ammassi rocciosi in un contesto alpino, la cui previsione, in fase di indagine preliminare, può contribuire alla definizione del modello geomeccanico di riferimento e quindi alla pianificazione dei progetti d’ingegneria civile e mineraria. Il presente lavoro si pone come obiettivo la stima delle proprietà geomeccaniche su una vasta area, utilizzando tecniche geostatistiche. L’area di studio, in Val San Giacomo (SO), ha un’estensione di circa 200 km2 e comprende litotipi riconducibili al Dominio Pennidico, rappresentato dalle falde di ricoprimento Tambò e Suretta, separate dalla Sinclinale dello Spulga. Sui principali e più accessibili affioramenti, in accordo con la metodologia ISRM, sono stati eseguiti rilievi geomeccanici di dettaglio e definite sia le proprietà geomeccaniche sia gli indici di qualità degli ammassi rocciosi. Per stimare tali proprietà, ed in particolare il grado di fratturazione, al di fuori dei punti di campionamento, sono state applicate diverse tecniche geostatistiche. Dopo aver effettuato l’analisi esplorativa spaziale dei dati dell’intercetta delle discontinuità e dell’indice di fratturazione volumetrica – Jv – si è condotto uno studio variografico multi scala per l’identificazione delle strutture di correlazione spaziale, successivamente la stima è stata eseguita utilizzando sia il metodo del kriging ordinario sia quello della simulazione Gaussiana sequenziale. La validazione, effettuata su un data set indipendente, ha mostrato che i migliori risultati, ottenuti stimando il Jv, derivano dalla simulazione Gaussiana sequenziale, che rispetta anche i valori estremi della distribuzione
TOWARDS THE COMPREHENSION OF ROCKFALL MOTION, WITH THE AID OF IN SITU TESTS
Full text linkRockfalls frequently occur in Alpine areas, creating serious risks to population and buildings; the protection measures against rockfalls cannot be adequately designed unless the comprehensive understanding of rockfall phenomenon. Some experimental rockfall tests have been performed on a talus slope in Grosina Valley (northern Italy), with the aim to check the reliability of common simulation methods and to analyse the motion of falling blocks. First, a-priori kinematic simulations have been performed, and, after the rockfall tests, the results have been compared with the real stopping positions of blocks. Afterwards, the recorded trajectories of falling blocks have been analysed, allowing the calculation of the motion parameters of falling blocks. The motion of blocks was mainly characterized by rebounds, therefore particular attention has been paid to restitution coefficients, which describe the loss of energy during the impact and greatly affect the results of rockfall simulations. Although the talus slope features are quite constant, an unexpected wide range of restitution coefficients results from the movies: the variability is greater than that one of bibliography, moreover normal restitution coefficients are extremely high (they often overpass the unit). The qualitative relationships between restitution coefficients and slope features, falling block characteristics and pre-impact motion conditions have been searched and described
Rock Mass Rating spatial estimation by geostatistical analysis
Full text linkThis work aims to estimate the Rock Mass Rating of 200km2 area of the Italian Central Alps, along San Giacomo Valley (province of Sondrio). The regional geological setting is related to the Pennidic Nappe arrangement, which is characterized by the emplacement of sub-horizontal gneissic bodies, separated by meta-sedimentary cover units. The resulting RMR map can be a useful tool to forecast the quality of outcropping rock masses as well as to derive their geomechanical behaviour. Almost 100 geomechanical field surveys have been carried out in the research area, in order to characterize the outcropping rock masses; afterwards rock mass quality indexes have been evaluated in each surveyed site. In order to estimate the Rock Mass Rating values in un-sampled locations, different geostatistical techniques (kriging and simulations) have been applied, using both bi-dimensional and almost three-dimensional approaches. The validation process shows that kriging tends to produce smoothened distributions, while conditional simulations allow respecting local extreme values. Although geostatistical analysis reveals that geomechanical properties show spatial correlations, it is to remind that rock mass quality is strongly related to its geological and structural history
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