Φαινόμενα ρευστοποίησης εδαφών στον ελληνικό χώρο
Creators: name: Παπαθανασίου, Γεώργιος Β.
Publisher: name: Aristotle University of Thessaloniki
Year: 2006
Subjects: Εδαφικές αστοχίες
Πρόβλεψη επιφανειακών εμφανίσεων
Ground failures
Prediction of surface manifestation

description: Στόχος της παρούσας διατριβής είναι η μελέτη του φαινομένου της ρευστοποίησης στον ελληνικό χώρο. Για την επίτευξη του στόχου αναζητήθηκε ιστορικά περιστατικά εμφανίσεων ρευστοποίησης σε σεισμικούς καταλόγους και επιστημονικές εργασίες. Τα αποτελέσματα τα οποία πρόέκυψαν από αυτή την αναζήτηση και αξιολόγηση των περιγραφών είναι α)δημιουργία καταλόγου εμφάνισης ρευστοποίησης, β)σύνταξη χάρτη επιδεικτικότητας προς ρευστοποίηση περιοχών του ελληνικού χώρου, γ)νέες εμπειρικές σχέσεις υπολογισμού της απόστασης εμφάνισης φαινομένου ρευστοποίησης. Επειτα κρίθηκε σκόπιμο να επεκταθεί η έρευνα στον τομέα της πρόβλεψης επιφανειακών εκδηλώσεων ρευστοποίησης. Τα αποτελέσματα από αυτήν την διερεύνηση είναι δ)ανάπτυξη μεθόδου υπολογισμού της πιθανότητας εκδήλωσης φαινομένων ρευστοποίησης, ε)ανάπτυξη συνάρτησης διάκρισης εμφάνισης ή μη φαινομένων ρευστοποίησης και στ)ταξινόμηση μορφών αστοχιών ρευστοποίησης
description: The goal of this research was to investigate the appearance of liquefaction phenomena in the broader Aegean region and to propose new empirical relationships correlating the earthquake magnitude with the epicentral distance of the liquefied site. Furthermore, the probability of liquefaction surface occurrences has been studied using the liquefaction potential index of the soil column. In order to achieve these goals, the author collected historical and seismotectonic data from the broader Aegean region that are relevant to liquefaction phenomena and geotechnical profiles of liquefaction/non liquefaction sites from several parts of the world. Initially, a database of liquefaction-induced ground failures and structural damages sites was produced based on descriptions from seismic catalogues concerning the broader Aegean region. These liquefaction cases histories have been triggered by 88 earthquakes since 1509. However, the proposed correlations were only based on data reported to the instrumental era (after 1900), providing an accurate and reliable tool for the liquefaction hazard assessment. Based on these data, an upper bound of maximum epicentral distance (Remax) for a given earthquake magnitude Ms was calculated. The regression of this boundary is: Ms=4.742+4.655.1 3Remax+0,8097.log(Remax). The lower limit of earthquake magnitude that induced liquefaction in the study area is Ms=5.0, while the upper limit is Ms=7.6. The relatively equation for Greece is: Ms=5.3225e 0.0046Remax. Furthermore, the closest distance of the liquefied sites to the causative faults was estimated in order to determine a distance - magnitude relation. The calculated regression that is suggested is: Ms =5.224+7.34.10-3 Rfmax +0.488.log(Rfmax) for 5.5&lt; Ms&lt;7.1 and it concerns normal faulting data. The strike-slip faulting data were few and the attempt to estimate regression for this category of faulting was unsuccessful. In addition, an attempt was made to calculate regressions of Re on Ms, according to the focal mechanism of the event. In what concerns the normal faulting data, the equation of the best-fit curve and the upper bound curve are: Ms = 0.01 . Re + 6.38 ± 0.38 (the last term in equation expresses the standard deviation of the predicted value), and Ms = 0.021 . Remax + 5.3 respectively for Ms values between 5.5 and 7.1. In the second database that was produced during this research, SPT profiles from liquefaction/non liquefaction sites are presented. To achieve an accurate and reliable result, strict protocols were established for processing data based on the quality of information. Afterwards, the selected data were analyzed using the method of logistic regression, the discriminant analysis and the whisker box-plot method. This research resulted in a new SPT-based probabilistic method for the prediction of liquefaction surface evidence using the value of the Liquefaction Potential Index of the soil column. Moreover, a discriminant function based on the value of LPI and the thickness of the non-liquefiable cap layer is presented. Using this equation, a site can be classified as likely or not to liquefy. Finally, the severity of liquefaction-induced damages was classified based on the value of LPI. The proposed correlation indicates that for LPI&gt;32 lateral spreading phenomena should be expected, for 11.5