On September the 4th 1618 the city of Piuro in Valchiavenna was buried by a very large landslide. The thesis work focuses on identifying the thickness of the landslide and the levels of collapses that occurred subsequently and on characterizing the mechanical properties of the material involved. In order to obtain this information, HVSR (Horizontal to Vertical Spectral Ratio) tests were performed. The technique in question consists in the recording of seismic waves generated by environmental micro-tremors, therefore by uncontrolled sources. The management and processing of the experimental data acquired in the field was addressed with the Geopsy software, essential for identifying the fundamental frequency of each measuring point. Geophysical investigations are based on the presence of mechanical contrasts between the materials investigated. The HVSR passive seismic analysis was correlated to MASW (Multichannel Analysis of Seismic Waves), to Down-Hole, to VSP (Vertical Seismic Profile) tests and to the analysis of an extracted sample. This comparison is necessary to evaluate the conditions site and verify the presence of physical principles essential for the effectiveness of the method. The final chapter then discusses the results of the different approaches and the feasibility of a study of the area with geophysical methods for the reconstruction of the stratigraphic profile of the landslide in Valchiavenna.
Il 4 settembre del 1618 l'abitato di Piuro in Valchiavenna venne sepolta da una frana molto estesa. L’elaborato di tesi si focalizza sull’identificazione dello spessore del corpo di frana e dei livelli di crolli avvenuti successivamente e sulla caratterizzazione delle proprietà meccaniche del materiale coinvolto. Al fine di ricavare queste informazioni sono state eseguite prove HVSR (Horizontal to Vertical Spectral Ratio). La tecnica in questione consiste nella registrazione di onde sismiche generate da microtremori ambientali, quindi da sorgenti non controllate. La gestione e l’elaborazione dei dati sperimentali acquisiti in campo è stata affrontata con il software Geopsy, indispensabile per l’identificazione della frequenza di risonanza di ciascun punto di misura. Le indagini geofisiche si basano sulla presenza di contrasti meccanici tra i materiali investigati. L’analisi di sismica passiva a singola stazione HVSR è stata correlata a prove MASW (Multichannel Analysis of Seismic Waves), Down-Hole, VSP (Vertical Seismic Profile) e all’analisi di un campione estratto tramite carotiere, necessari per valutare le condizioni di sito e verificare la presenza di principi fisici indispensabili per l’efficacia del metodo. Nel capitolo conclusivo vengono quindi discussi gli esiti dei differenti approcci e la fattibilità di uno studio dell’area con metodi geofisici per la ricostruzione del profilo stratigrafico del corpo di frana in Valchiavenna.
Analisi di fattibilità sull'utilizzo di metodi geofisici per lo studio della frana di Piuro (SO)
Zinetti, Anna
2019/2020
Abstract
On September the 4th 1618 the city of Piuro in Valchiavenna was buried by a very large landslide. The thesis work focuses on identifying the thickness of the landslide and the levels of collapses that occurred subsequently and on characterizing the mechanical properties of the material involved. In order to obtain this information, HVSR (Horizontal to Vertical Spectral Ratio) tests were performed. The technique in question consists in the recording of seismic waves generated by environmental micro-tremors, therefore by uncontrolled sources. The management and processing of the experimental data acquired in the field was addressed with the Geopsy software, essential for identifying the fundamental frequency of each measuring point. Geophysical investigations are based on the presence of mechanical contrasts between the materials investigated. The HVSR passive seismic analysis was correlated to MASW (Multichannel Analysis of Seismic Waves), to Down-Hole, to VSP (Vertical Seismic Profile) tests and to the analysis of an extracted sample. This comparison is necessary to evaluate the conditions site and verify the presence of physical principles essential for the effectiveness of the method. The final chapter then discusses the results of the different approaches and the feasibility of a study of the area with geophysical methods for the reconstruction of the stratigraphic profile of the landslide in Valchiavenna.| File | Dimensione | Formato | |
|---|---|---|---|
|
2020_07_Zinetti.pdf
non accessibile
Descrizione: Testo tesi
Dimensione
23.69 MB
Formato
Adobe PDF
|
23.69 MB | Adobe PDF | Visualizza/Apri |
I documenti in POLITesi sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
https://hdl.handle.net/10589/164571