757 research outputs found

    The engineering geological behaviour of disturbed and weatherd gneiss in slopes. The case of the "vertical axis" of Egnatia motorway, Komotini - Nymfea, Northern Greece.

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    Ο υγιής γνεύσιος διαμορφώνει πολύ ικανές βραχόμαζες με περιορισμένα προβλήματα στα γεωτεχνικά έργα. Ασθενείς όμως βραχόμαζες και προβληματικές συμπεριφορές μπορεί να προκύψουν στα τεχνικά έργα μέσα σε ένα γεωλογικό περιβάλλον που χαρακτηρίζεται από έντονη, πολλαπλών φάσεων, τεκτονική διαταραχή όπου ευνοείται η αποσάθρωση. Στην παρούσα εργασία παρουσιάζεται η συμπεριφορά των γνευσιακών βραχομαζών στην διαμόρφωση ορυγμάτων κατά μήκος της Εγνατίας Οδού στον κάθετο άξονα Κομοτηνή-Νυμφαία. Τα κύρια τεχνικογεωλογικά χαρακτηριστικά εντοπίζονται στον βαθμό αποσάθρωσης, στη τεκτονική διαταραχή, στην ένταση της σχιστότητας και στην παρουσία διατμημένων ζωνών. Στο άρθρο αυτό οι βραχόμαζες κατηγοριοποιούνται σε τύπους  ανάλογα με τα τεχνικογεωλογικά χαρακτηριστικά – «κλειδιά»- που ορίζουν τη συμπεριφορά τους στα πρανή. Έτσι, εξετάζεται ο πιθανότερος μηχανισμός αστοχίας στην διαμόρφωση πρανών για κάθε τύπο βραχόμαζας. Οι γεωτεχνικές ιδιότητες των επιφανειών αυτών είναι αρκετά δύσκολο να εκτιμηθούν λόγω της φύσης των γεωυλικών που αναπτύσσονται σε αυτές ενώ οι ανάστροφες αναλύσεις είναι η καλύτερη μέθοδος για να προσδωθούν αξιόπιστες παράμετροι σχεδιασμού. Εδώ παρουσιάζονται τα αποτελέσματα δύο ανάστροφων αναλύσεων, μία για πλήρως αποσαθρωμένο γνεύσιο και μία για διατημένες επιφάνειες. Τα αποτελέσματα αυτά παρουσιάζουν σημαντικές διαφορές με τις εργαστηριακές δοκιμές. Τέλος, συζητούνται πιθανά μέτρα σταθεροποίησής ανάλογα με τον μηχανισμό αστοχίας για τις δύο περιπτώσεις.Sound gneiss forms evidently very competent rock masses with minor problems in geotechnical works. However, poor rock masses and problematic behaviour can be encountered in engineering projects in a geological environment characterized by intensive and sequent tectonic disturbance, where, weathering may be strongly favoured. Case studies with slope instability problems are analysed from the Egnatia Motorway along the vertical axis from Komotini to Nymfea, in Northern Greece. The basic engineering geological consideration focuses on the weathering degree, the tectonic disturbance, the foliated structure and the presence of shear zones. In the paper the gneissic rock masses are categorized in a number of specific rock mass types according to key engineering geological characteristics that define the rock mass behaviour in slopes. Subsequently, the slope behaviour of each rock mass type is discussed. The geotechnical properties of such failure surfaces are very difficult to be estimated due to the heterogeneous nature of these planes and back analysis is the best method to obtain reliable parameters. Back analysis results from two case studies showed significant differences to the laboratory test results. Finally, the concepts of the appropriate support measures based on the mechanism of failure of two case studies are presented in the paper

    LABORATORY INVESTIGATION ON THE CORRELATION BETWEEN THE FRICTION ANGLE OF ROCK JOINTS AND THE CONSTANT MI OF THE HOEK AND BROWN CRITERION

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    Στην παρούσα εργασία διερευνάται η συσχέτιση μεταξύ της μη - διαστολικής γωνίας τριβής (φm ) ασυνεχειών και της σταθεράς mi του κριτηρίου Hoek and Brown για τον άρρηκτο βράχο, με τη χρήση των αποτελεσμάτων ενός προσανατολισμένου προγράμματος εργαστηριακών δοκιμών. Το πρόγραμμα περιλαμβάνει δύο τύπους εργαστηριακών δοκιμών: μια σειρά από δοκιμές τριαξονικής θλίψης σε ακέραια δείγματα πετρωμάτων για τον προσδιορισμό του mi και μια ανεξάρτητη σειρά δοκιμών άμεσης διάτμησης ασυνεχειών σε επιφάνειες ασυνεχειών, που προέκυψαν από εφελκυστική αστοχία από τα ίδια πετρώματα για τον προσδιορισμό του φm. Χρησιμοποιήθηκαν τέσσερις αντιπροσωπευτικοί τύποι πετρωμάτων από τη Βόρεια Ελλάδα: ένας γρανίτης, ένας ψαμμίτης, ένας ασβεστόλιθος και ένα μάρμαρο, καλύπτοντας ένα εύρος τιμών mi μεταξύ 8 και 34, και αντοχής σε ανεμπόδιστη θλίψη μεταξύ 60 και 120 MPa. Εκτός από το εύρος των παραμέτρων που παρουσιάζεται για τα 4 αυτά συγκεκριμένα πετρώματα, τα πειραματικά αποτελέσματα δείχνουν ότι η χωρίς διαστολή γωνία τριβής της ασυνέχειας βράχου που προσδιορίζεται από τη δοκιμή άμεσης διάτμησης (φm) μειώνεται λογαριθμικά με την τιμή της σταθεράς mi.A correlation between the non-dilational friction angle (φm) of rock discontinuities and the constant mi of the Hoek and Brown criterion for intact rock is investigated, using the results of a focus oriented laboratory program. The program consisted of two types of laboratory tests: a series of triaxial compression tests on intact rock samples for the determination of the constant mi and an independent series of direct shear tests on tensile fractures of the same rock types for the determination of the rock joint friction angle φm. Four typical rock types from Northern Greece were used: a granite, a sandstone, a limestone and a marble, covering a range of mi between 8 and 34, and an unconfined compressive strength between 60 and 120 MPa. Apart from the certain range of parameters that is presented for this specific rocks, the experimental results show that the non-dilational friction angle of the rock fracture determined by direct shear testing (φm) decreases logarithmically with the value of the constant mi

    Sustainable treatment method of a high concentrated NH3 wastewater by using natural zeolite in closed-loop fixed bed systems

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    The aim of this study is to investigate ammonium removal from a wastewater resulted after homogenization and anaerobic digestion of a mixture of wastes and wastewater from animal processing units and sewage sludge, by using natural zeolite clinoptilolite. Batches as well as closed loop fixed bed system (CLFB) are studied, offering an alternative to conventional fixed bed systems. The experimental results showed that the optimum pH is in the vicinity of 6.48, where the achieved removal in the batch system reached 46%. The CLFB system, under the same experimental conditions and relative flow rate of 2.56 BV h−1, reached a removal of 55%, which is almost 22% higher. In the CLFB the removal of ammonia could be further increased by diluting the initial solution by 1/8, reaching the level of 96%. The achieved zeolite loading, for all studied systems, is between 2.62 and 13 mg g−1. This kind of operation is very useful for relatively high concentration and small volumes of wastewater and in systems that there is no need for continuous flow operation

    The Steady-State Multi-TeV Diffuse Gamma-Ray Emission Predicted with GALPROP and Prospects for the Cherenkov Telescope Array

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    Cosmic Rays (CRs) interact with the diffuse gas, radiation, and magnetic fields in the interstellar medium (ISM) to produce electromagnetic emissions that are a significant component of the all-sky flux across a broad wavelength range. The Fermi Large Area Telescope (LAT) has measured these emissions at GeV γ\gamma-ray energies with high statistics. Meanwhile, the High-Energy Stereoscopic System (H.E.S.S.) telescope array has observed large-scale Galactic diffuse emission in the TeV γ\gamma-ray energy range. The emissions observed at GeV and TeV energies are connected by the common origin of the CR particles injected by the sources, but the energy dependence of the mixture from the general ISM (true `diffuse'), those emanating from the relatively nearby interstellar space about the sources, and the sources themselves, is not well understood. In this paper, we investigate predictions of the broadband emissions using the GALPROP code over a grid of steady-state 3D models that include variations over CR sources, and other ISM target distributions. We compare, in particular, the model predictions in the VHE (\geq100 GeV) γ\gamma-ray range with the H.E.S.S. Galactic plane survey (HGPS) after carefully subtracting emission from catalogued γ\gamma-ray sources. Accounting for the unresolved source contribution, and the systematic uncertainty of the HGPS, we find that the GALPROP model predictions agree with lower estimates for the HGPS source-subtracted diffuse flux. We discuss the implications of the modelling results for interpretation of data from the next generation Cherenkov Telescope Array (CTA).Comment: 14 pages, 12 figures, Accepted in MNRA

    Endometrial Cancer: What Is New in Adjuvant and Molecularly Targeted Therapy?

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    Endometrial cancer is the most common gynaecological cancer in western countries. Radiotherapy remains the mainstay of postoperative management, but accumulating data show that adjuvant chemotherapy may display promising results after staging surgery. The prognosis of patients with metastatic disease remains disappointing with only one-year survival. Progestins represent an effective option, especially for those patients with low-grade estrogen and/or progesterone receptor positive disease. Chemotherapy using the combination of paclitaxel, doxorubicin, and cisplatin is beneficial for patients with advanced or metastatic disease after staging surgery and potentially for patients with early-stage disease and high-risk factors. Toxicity is a point in question; however, the combination of paclitaxel with carboplatin may diminish these concerns. In women with multiple medical comorbidities, single-agent chemotherapy may be better tolerated with acceptable results. Our increased knowledge of the molecular aspects of endometrial cancer biology has paved the way for clinical research to develop novel targeted antineoplastic agents (everolimus, temsirolimus, gefitinib, erlotinib, cetuximab, trastuzumab, bevacizumab, sorafenib) as more effective and less toxic options. Continued investigation into the molecular pathways of endometrial cancer development and progression will increase our knowledge of this disease leading to the discovery of novel, superior agents
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