Rockfall hazard and risk assessment of road slopes.

Οι καταπτώσεις βράχων σε οδικές αρτηρίες, οδηγούν σε σημαντικές επιπτώσεις και συνεπώς είναι ιδιαίτερα σημαντική η εκτίμηση του επιπέδου της επικινδυνότητας σε πρανή οδοποιίας και η λήψη μέτρων προστασίας. Στην παρούσα εργασία συγκρίνονται οι σημαντικότερες μέθοδοι εκτίμησης της επικινδυνότητας και της διακινδύνευσης καταπτώσεων βράχων. Όσον αφορά την επικινδυνότητα, λαμβάνονται υπόψη παράμετροι όπως η γεωμετρία του πρανούς, οι κυκλοφοριακές συνθήκες, η γεωλογία και τα χαρακτηριστικά της βραχόμαζας, οι καιρικές συνθήκες, τα ιστορικά δεδομένα, κ.α. Εκτίμηση της επικινδυνότητας μπορεί επίσης να προκύψει μέσω δισδιάστατων ή τρισδιάστατων μοντέλων προσομοίωσης τροχιάς, όπου συνδυάζονται τα δεδομένα της συχνότητας βραχοπτώσεων με την κινητική ενέργεια του καταπίπτοντος τεμάχους βράχου. Όσον αφορά την εκτίμηση της διακινδύνευσης, έχουν αναπτυχθεί διάφορες μέθοδοι, που ποικίλουν από απλοϊκές προσεγγίσεις, έως ολοκληρωμένες πιθανολογικές ή ποσοτικές μέθοδοι. Τέλος, ως παράδειγμα, χρησιμοποιήθηκαν οι καταλληλότερες μέθοδοι εξ αυτών για την εκτίμηση της επικινδυνότητας και διακινδύνευσης από καταπτώσεις βράχων, σε δύο τυπικές διατομές της Εθνικής Οδού Αθηνών – Θεσσαλονίκης, στο τμήμα των Τεμπών, όπου έχουν καταγραφεί αρκετά συμβάντα καταπτώσεων βράχων τα τελευταία χρόνια.This paper presents and compares the main methods of hazard and risk assessment for road slopes. Hazard assessment is achieved by rating several parameters such as the slope’s geometry, traffic conditions, the geology and the rockmass properties, weather conditions, historical rockfall data etc. A hazard assessment can also be executed using 2D or 3D trajectory models, by combining the frequency of a rockfall and the kinetic energy of a falling rock. Several methodologies have been developed for risk assessment, varying from simplistic approaches to comprehensive probabilistic or quantitative risk assessment methods. Finally, the most suitable methods were used in order to assess the level of hazard and risk as an example (the data from two sections of the national road at Tempi Gorge, Greece) where many rockfall events occurred in the past few years

Middle-class Housing as a Cross-cultural and Multi-disciplinary Project: Rethinking Critical, Interpretative and Methodological Frameworks

The history of the modernization processes of post-WWII European cities could be observed through the lens of the emerging middle classes between the 1950s and the 1970s when housing significantly contributed to establishing and defining new social identities. Middle classes were the main protagonists of the rapid urban development and massive expansion that profoundly influenced the production of new estates, neighborhoods, and urban sectors, leaving relevant traces on the contemporary built environment of the European cities. In a sense, Europe, in its various civic configurations and cultural representations, became the symbol of progress and prosperity for the middle classes, an international formation restored and restructured by the middle classes which was meant to serve and protect according to a new post-war social contract

Rockfalls: influence of rock hardness on the trajectory of falling rock blocks.

Οι καταπτώσεις βράχων θέτουν σε σημαντικό κίνδυνο τις ανθρώπινες δραστηριότητες και τις υποδομές. Η εκτίμηση του κινδύνου αυτού κατά μήκος οδών και άλλων ανθρώπινων δραστηριοτήτων έχει ιδιαίτερη σημασία. Με κατάλληλη γεωλογική αξιολόγηση είναι δυνατόν να προβλεφθούν οι επισφαλείς θέσεις έναντι καταπτώσεων, να εξηγηθεί ο μηχανισμός ενεργοποίησης του φαινόμενου και να καταστεί αποτελεσματικότερος ο σχεδιασμός των μέτρων προστασίας. Η τροχιά ενός τεμάχους επηρεάζεται σημαντικά από την αλληλεπίδρασή του με το πρανές κατά την κρούση, όπου οι κινηματικές συνθήκες του τεμάχους μεταβάλλονται ανάλογα με τους συντελεστές αναπήδησης. Για την διερεύνηση των ιδιοτήτων των πετρωμάτων που επηρεάζουν τους συντελεστές αναπήδησης πραγματοποιήθηκε εργαστηριακή έρευνα που βασίζεται στην ελεύθερη πτώση τεμαχών διαφορετικών βραχωδών και τεχνητών υλικών. Από την εργαστηριακή διερεύνηση προτείνεται μια συσχέτιση του συντελεστή αναπήδησης με την σκληρότητα που προσδιορίζεται με τη σφύρα Schmidt.Rockfalls pose significant hazard on human activities and infrastructure. The assessment of rockfall risk along roads and on other human activities is of great importance. Geological assessment can predict the outbreak of such events; explain the mechanism of occurrence and assist in the effective design of protection measures. The trajectory of a falling block is significantly affected by its response to the impact with the slope, since block kinematics properties mainly depend on the coefficient of restitution values. In this research a laboratory procedure based on the free fall of small blocks of different rock types and artificial materials was implemented in order to address the effect of their mechanical properties on the coefficient of restitution values. From the evaluation of testing results a correlation between kinematic coefficient of restitution and Schmidt rock hardness is proposed

Rockfall hazard and risk assessment: an example from a high promontory at the historical site of Monemvasia, Greece

The paper presents the kinematics of rock instability of a high limestone promontory, where the Monemvasia historical site is situated, in Peloponnese in Southern Greece. The instability phenomena poses a significant threat to the town located at the base of the slope. Rockfall episodes occurred in the past due to the relaxation of the high cliff, whereas significant undermining of the castle frontiers has been observed at the slope crest. <br><br> The predominant types of instability are of planar, wedge and toppling failure of medium to large blocks. In order to investigate the existing stability conditions and decide upon the protection measures, stability and rockfall analyses were carried out for numerous slope sections under different loading conditions and protection measures were suggested. <br><br> A rock-fall risk rating system is proposed, which is based on morphological and structural criteria of the rock mass and on vulnerability and consequences. The rating system is applied for individual sections along the slope and a risk map was produced, which depicted areas having different degree of risk against rockfall occurrences

Slope Stability Problems Related to a Semi-Bridge Construction

In the area of AKTEA , a summer-housing estate 36 Km away from the city of Athens, a great landslide affected the stability of a semi-bridge, constructed in 1980 for the widening of the nearby national road. Preliminary studies carried out before the semi-bridge construction and after the observed damage of most of the houses in the uphill area, favoured the existence of a very superficial creep affecting however the one or two storey buildings of the summer-housing estate. After the semi-bridge construction, instability phenomena continued in an increasing rate and a more systematic geotechnical investigation revealed definite landslide movements (instead of a superficial creep) in a depth 2.5 to 4.0 metres below the foundation level of the piers of the semi-bridge and in a depth 6-8 m below the road level. This paper describes details of the above landslide, the investigations carried out and the remedial measures suggested

Geotechnical Problems in a Bridge over Corinth Canal

The railroad bridge of Corinth Canal was founded in a stable tectonic block (horst) consisting of neogene marly limestones, marls and sands. After the last strong earthquake of 24th February 1981 an extension of existed subvertical joints, directed E-W, was observed close to the northern bridge abutment. A geotechnical study was carried out for the detection of the causes which created these phenomena and for the design of probable reinforcing measures. From the results of site investigations and laboratory tests and after considering the slope stability, it was concluded that the only risk for the abutment is the progressive change of joints apperture and their erosion due to rain water. To minimize this risk, the installation of inclined untensioned grouted dowels was proposed and the continuous monitor of joints apperture especially during future strong earthquakes

Architettura, narrazione e l'arte di vivere

This paper draws from the idea of philosophy as a “life art” - as discussed by philosopher Alexander Nehamas in his book The Art of Living - in order to highlight a hidden connection between architecture, as a creative practice, and the narration of the self.Can the criteria for a great architecture be reduced to standards and values that are deemed ‘universal’? Or should concepts such as “originality”, “authenticity”, and “uniqueness” be regarded context-dependent and determined retrospectively, only relevant within the narration of a unique personal creative course?Through a short, imaginary story - which is based on actual historical events - I will argue that the value and impact of every architectural creation cannot always be inherently defined but are usually directly related to what is called “the care of the self”. What I intend my story to tell is that no ‘recipe’ for great architecture exists for someone to follow, precisely because every exemplary architectural creation is always constructed on the scaffolding of an exemplary life. Exemplary not in a moral sense, but in the aesthetic sense of a narration related to the art of living.Likewise, if every influential architectural work is based on a personal biography then the creative potential of architecture cannot but be intertwined with the question of a narration of the self that is focused on the self-construction of the architect as a person.At the same time narration is often used as a means to transcend the objective foundations and limits of architectural creation and in order to further establish a social distinction; a distinction (in Bourdieuan terms) between the architects and the Architect. From Le Corbusier and Louis Kahn to Rem Koolhaas and Bjarke Ingels the various efforts to narrate a unique biography are nothing but rhetorical techniques used in the framework of a persuasion strategy. The moral of all these narratives is that the person actually matters more than the project. In other words, architecture’s value, impact and command are related to the creation of the architect as a person as much as - if not more than - architectural creation itself.Questo articolo trae spunto dall'idea della filosofia come "arte di vivere" - sostenuta dal filosofo Alexander Nehamas nel suo libro The Art of Living – con lo scopo di evidenziare una connessione nascosta tra l'architettura come pratica creativa e la narrazione del sé .Le caratteristiche di una grande architettura possono essere ricondotte a standard e valori "universali"? O invece concetti come "originalità", "autenticità" e "unicità" devono essere considerati come legati a un contesto e determinati a posteriori, rilevanti solo in relazione al racconto di un percorso creativo personale?Attraverso una breve storia immaginaria - basata su eventi storici reali - sosterrò che il valore e l'impatto di una creazione architettonica non possono essere sempre definiti intrinsecamente, ma di solito sono direttamente correlati a ciò che viene chiamato "la costruzione del sé". Ciò che intendo dire nella mia storia è che non esiste nessuna "formula" da seguire per la grande architettura, proprio perché ogni creazione architettonica esemplare è sempre costruita sull'impalcatura di una vita esemplare. Esemplare non in senso morale, ma nel senso estetico di una narrazione legata all'arte del vivere.Allo stesso modo, se ogni influente opera architettonica si basa su una biografia personale, allora il potenziale creativo dell'architettura non può che essere intrecciato con la questione di una narrazione del sé incentrata sull'auto-costruzione dell'architetto come persona.Allo stesso tempo, la narrazione è spesso usata come mezzo per trascendere le basi e i limiti oggettivi della creazione architettonica e stabilire una distinzione sociale; una distinzione (nell’accezione di Bourdieu) tra gli architetti e l'Architetto. Da Le Corbusier e Louis Kahn a Rem Koolhaas e Bjarke Ingels i diversi sforzi per narrare una biografia singolare non sono altro che tecniche retoriche usate nel quadro di una strategia di persuasione. La morale di tutte queste narrative è che la persona conta davvero più del progetto. In altre parole, il valore, l'impatto e l’autorevolezza dell'architettura sono legati alla creazione dell'architetto come persona tanto quanto - se non più - della stessa creazione architettonica