Διερεύνηση μηχανικών ιδιοτήτων και ταξινόμηση ασθενών τεκτονισμένων πετρωμάτων με εφαρμογή στη δυτική Λευκάδα

Καλλιμογιάννης, Βασίλειος; Kallimogiannis, Vasileios

dc.contributor.author	Καλλιμογιάννης, Βασίλειος	el
dc.contributor.author	Kallimogiannis, Vasileios	en
dc.date.accessioned	2023-03-27T08:06:42Z
dc.date.available	2023-03-27T08:06:42Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/57322
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.25020
dc.rights	Αναφορά Δημιουργού-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nd/3.0/gr/	*
dc.subject	Ασθενή τεκτονισμένα πετρώματα	el
dc.subject	Μηχανικές ιδιότητες	el
dc.subject	Ταξινόμηση	el
dc.subject	Εργαστηριακές δοκιμές	el
dc.subject	Ανάστροφες αναλύσεις κατολισθήσεων	el
dc.subject	Λευκάδα (Ελλάδα)	el
dc.subject	Mechanical properties	en
dc.subject	Lefkada island (Greece)	en
dc.subject	Carbonate fault rocks	en
dc.title	Διερεύνηση μηχανικών ιδιοτήτων και ταξινόμηση ασθενών τεκτονισμένων πετρωμάτων με εφαρμογή στη δυτική Λευκάδα	el
dc.title	Investigation of the and classification of weak carbonate fault rocks with application in western Lefkada island, Greece	en
heal.type	doctoralThesis
heal.classification	Γεωτεχνική Μηχανική	el
heal.classification	Βραχομηχανική	el
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2023-02-22
heal.abstract	Weak rocks comprise a significant percentage of the earth’s crust and often present poor mechanical properties, such as high deformability and low shear strength. They are frequently encountered in civil engineering projects, but the investigation of their properties is disproportional to the extent of their appearance and the critical issues that they cause. The reason of this lack of investigation is their complex nature, given that they often comprise heterogeneous materials, intensely fractured that are difficult or even impossible (in some cases) to sample, thus disallowing both in-situ and/or laboratory testing. In an attempt to fill this gap, the first goal of this PhD thesis is to quantify the physical properties and the mechanical behavior of a specific type of weak rock using laboratory testing, in-situ investigation and back-analyses of co-seismic landslides that occurred in this material. The second goal of this PhD thesis is to use the foregoing findings for providing an effective classification system for such weak rocks. This is important, because the existing classification systems in rock mechanics have specific limitations and may not always fully apply for estimating the behavior of weaker materials. For the tasks at hand, the focus is put on a weak rock of tectonic origin found in the western slopes of Lefkada island, Greece. In more detail, the studied rocks are carbonate formations that have deteriorated to weak fault breccias, or fractured-disintegrated limestones and dolomites due to the impact of tectonic disturbance. Similar formations are widely found in numerous locations across Greece, but also around the world. The first goal is accomplished with: (a) in-situ investigations to characterize the carbonate formations and assess their textural/structural components performed via expeditions between 2017 and 2021 in Lefkada island, (b) derivation of the in-situ shear strength of limestone fault breccias and highly fractured limestones via a series of back-calculation analyses of UAV-mapped co-seismic landslides that occurred during the Mw 6.5 earthquake that struck Lefkada island in November 2015, (c) execution of laboratory tests. Regarding item (c), it should be underlined here that there are incontrovertible limitations in performing a laboratory investigation on weak carbonate fault rocks using the typical methods suggested by the international standards (e.g., the International Society for Rock Mechanics, ISRM). As such, efficient innovative methods are employed for proper sampling and testing of these materials. Specifically, the laboratory tests are performed for two (2) types of intact parent limestones and five (5) types of fault rocks (two types of limestone fault breccia, one type of tectono-diagenetic dolomite breccia and two types of fractured marly limestone of tectonic origin). The fault rocks were mainly subjected to the Uniaxial Compression Test as their properties have not been studied in the past due to the practical limitations in sampling preparation. The results prove that the mechanical properties of the fault rocks are significantly reduced compared to their intact parent counterparts. In the three (3) brecciated types, the decay in the mechanical properties is related to textural features, i.e., the presence of matrix that bounds the carbonate fragments and the boundaries of reduced strength between the fragments and the matrix. The engineering behavior of the fractured marly limestones is controlled by structural features, i.e., the fracturing degree which allows pre-existing fractures to act as stress concentrators and lead to crack initiation and propagation in the early stages of the Uniaxial Compression Test. The back-analyses of stability of the co-seismic landslides indicate that the in-situ shear strength of limestone fault breccias corresponds to extremely weak rocks (ISRM, 1981) and is about one order of magnitude lower than that derived in the laboratory for the corresponding fault rock type. This is reasonable since the samples retrieved for laboratory testing were of higher quality compared to the material that comprises the failed studied slopes. The poor mechanical properties of the limestone fault breccias found in-situ are also related to the matrix that controls their overall behavior and is weaker than the matrix studied in the laboratory. Regarding the second goal of the thesis, the foregoing findings combined enable the derivation of a universal approach for characterizing and classifying the weak carbonate fault rocks. Specifically, these formations are classified into four (4) major groups: 1. Parent rocks, 2. Welded breccias, 3. Unwelded breccias and 4. Matrix. A distinct methodology to derive the intact rock strength is proposed based on the aforementioned classification. The impact of the fracturing degree is considered by introducing the Fault rocks Strength Reduction Factor (FSRF), which reduces the intact rock strength (UCSi) to the rock mass strength (UCSm). Finally, a new classification system (GSIFR) and a new disturbance factor D (DFR) are introduced and the Hoek-Brown failure criterion is modified to account for the behavior of weak carbonate fault rocks.	en
heal.advisorName	Παπαδημητρίου, Αχιλλέας	el
heal.committeeMemberName	Παπαδημητρίου, Αχιλλέας	el
heal.committeeMemberName	Ζέκκος, Δημήτριος	el
heal.committeeMemberName	Καββαδάς, Μιχαήλ	el
heal.committeeMemberName	Μπουκοβάλας, Γεώργιος	el
heal.committeeMemberName	Γεωργιάννου, Βασιλική	el
heal.committeeMemberName	Νομικός, Παύλος	el
heal.committeeMemberName	Μαρίνος, Βασίλειος	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Πολιτικών Μηχανικών. Τομέας Γεωτεχνικής	el
heal.academicPublisherID	ntua
heal.numberOfPages	681 σ.	el
heal.fullTextAvailability	false
heal.fullTextAvailability	false