ΔΙΕΡΕΥΝΗΣΗ ΕΠΙΡΡΟΗΣ ΥΔΡΑΥΛΙΚΩΝ ΣΥΝΘΗΚΩΝ ΣΤΗΝ ΕΥΣΤΑΘΕΙΑ ΤΟΥ ΜΕΤΩΠΟΥ ΕΚΣΚΑΦΗΣ ΑΒΑΘΩΝ ΣΗΡΑΓΓΩΝ

ΠΑΠΑΔΑΚΟΣ, ΑΝΑΣΤΑΣΙΟΣ

dc.contributor.author	ΠΑΠΑΔΑΚΟΣ, ΑΝΑΣΤΑΣΙΟΣ	el
dc.date.accessioned	2020-10-09T08:27:45Z
dc.date.available	2020-10-09T08:27:45Z
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/51341
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.19039
dc.rights	Αναφορά Δημιουργού-Μη Εμπορική Χρήση-Όχι Παράγωγα Έργα 3.0 Ελλάδα	*
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/gr/	*
dc.subject	ΥΔΡΑΥΛΙΚΕΣ ΣΥΝΘΗΚΕΣ, ΜΕΤΩΠΟ ΕΚΣΚΑΦΗΣ, ΕΥΣΤΑΘΕΙΑ, ΣΗΡΑΓΓΑ, ΑΒΑΘΗΣ	el
dc.subject	EXCAVATION FACE, TUNNEL, HYDRAULIC CONDITIONS, EPB, SHALLOW	en
dc.title	ΔΙΕΡΕΥΝΗΣΗ ΕΠΙΡΡΟΗΣ ΥΔΡΑΥΛΙΚΩΝ ΣΥΝΘΗΚΩΝ ΣΤΗΝ ΕΥΣΤΑΘΕΙΑ ΤΟΥ ΜΕΤΩΠΟΥ ΕΚΣΚΑΦΗΣ ΑΒΑΘΩΝ ΣΗΡΑΓΓΩΝ	el
dc.contributor.department	ΣΧΕΔΙΑΣΜΟΣ ΚΑΙ ΚΑΤΑΣΚΕΥΗ ΥΠΟΓΕΙΩΝ ΕΡΓΩΝ	el
heal.type	masterThesis
heal.classification	ΓΕΩΤΕΧΝΙΚΗ ΜΗΧΑΝΙΚΗ	el
heal.language	en
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2015-07-01
heal.abstract	The present Postgraduate Thesis deals with the subject of face stability demand in mechanically excavatedtunnels below the water table. More specifically, the effect of hydraulic conditions on the stability of the excavation face was thoroughly investigated throughmulti-parametric analyses that refer to EPB-bored, shallow tunnels, in fully saturated, clayey soil, during the excavation procedure. In order to achieve the aforementioned investigation, a set of ninety three (93) numerical, 3D-coupled analyses were carried out through the Finite Elementcode “Abaqus v.11.1”. The EPB machinewas modelled onlyas an equivalent pressure load on the working face without considering any other feature such as tail/annular voids, weight of the machine, geometry of the shield, grouting etc. because of their negligible effect on face stability. The aforementioned analyses concern specific geometrical characteristics (H/D) and hydrostatic initial stress field. Face stability was interpreted in terms of extrusion and radial wall convergence of the investigated cross section. In each set of analyses, geotechnical properties of the soil (c, φ, E, δ) were modified according to the Mohr-Coulomb failure criterion.Regarding the hydraulic conditions, the effect of the applied face pressure, soil permeability and advance rate of the machine wasparticularly investigated. The applied face pressure was correlated with the hydrostatic pressure at the crown of the shield. One of the basic modelling assumptions that had to be made in order to define the hydraulic boundary conditions of the problem,concernsthe muck’s condition. The muck was assumed to actas a viscous fluidthanks to effective soil conditioning. The latter means, in terms of modelling, that the applied face pressure (total pressure values) coincides with pore pressure values at each node of the face. Resulting face extrusion and radial wall convergence were evaluated in association with developed hydraulic phenomena such as excess pore pressure build up, suction, unfavorable seepage forces etc. Results are plottedversus the newly introduced stability factor 2Cu/γ’Η.The use of undrained shear strength parameter was verified as the results showed negligible variation of void ratio in all the investigated cases. To sum up, it was proved that the applied face pressure is decisiveregarding the stability of the face and thus pressure fluctuations have to be foreseen and avoided. Pore pressure values at the face (hydraulic boundaries) were found also to have a significant effect on face stability as they control the excavation-induced disturbance on the local hydraulic head field. Hydraulic boundaries at the working face depend on the condition of the muck indicating the major importance of soil conditioning. In parallel, decrease ofthe ground permeability or/and increase of the excavation advance rate up to feasible limits enhancethe stability of the face due to negative excess pore pressure development as the drainage conditions are hindered and vice versa. However, the effect of advance rate variation found to be significantly lower compared to that of permeability. Finally, investigation of hydraulic head field disturbance and its impact on deformations caused by consolidation of the muck showed that even a significant rise of effective stresses into the muck is not adequate to affect neither the anticipated deformations nor the hydraulic head distribution for the assumed permeability.	en
heal.advisorName	ΚΑΒΒΑΔΑΣ, ΜΙΧΑΗΛ	el
heal.committeeMemberName	ΣΟΦΙΑΝΟΣ, ΑΛΕΞΑΝΔΡΟΣ	el
heal.committeeMemberName	ΓΕΩΡΓΙΑΝΝΟΥ, ΒΑΣΙΛΙΚΗ	el
heal.committeeMemberName	ΚΑΒΒΑΔΑΣ, ΜΙΧΑΗΛ	el
heal.academicPublisher	Σχολή Πολιτικών Μηχανικών	el
heal.academicPublisherID	ntua
heal.numberOfPages	120
heal.fullTextAvailability	true