Η αξιολόγηση των τεχνικογεωλογικών και γεωτεχνικών συνθηκών σε σχέση με τη μηχανοποιημένη διάνοιξη σηράγγων

Abstract

The particular thesis has as an object to examine and analyze the geological and geotechnical conditions which are possible to be met by the face of the excavation of the tunnel of the Thessaloniki Metropolitan Railway construction from the Dimokratia station, which belongs to the main project, to Stauroupoli. From this analysis is going to be discussed the applicability of mechanized tunneling methods and the selection of the most appropriate for the excavation type of TBM. As a result of the complete development of the urban areas and the increase of private vehicle use in the recent years, the ability to construct roads which are going to cover the demand of quick and safe transport has been limited significantly. For this reason man has turned towards the exploitation of levels beneath the ground surface and the construction of underground, metropolitan railways in order to solve this problem. The construction of the Metropolitan Railway of Thessaloniki is an ambitious effort to fulfill this objective in a heavily urban environment while the main railway line consists of a 9.6km long tunnel and 13 stations. The extension to Stauroupoli, on which the thesis focuses on, consists of 5 stations and a 5km long tunnel, which is going to be developed initially in a plain environment with the altitude of the soil surface increasing up to 80m in the final part of the tunnel. The geology of the area of the extension is characterized of the presence of Quaternary, soil formations, which are located in the initial and final part of the tunnel, Neogene, soil formations, which are located mainly in the middle part of the tunnel and rocky formations which consist of Green Schists and belong to the Chortiatis Unit, which is the alpine base of the area. In this particular project the demand of the practice of mechanized tunneling methods comes from the necessity for quick completion of the construction and the minimization of the underground disturbance, as possible dangerous situations during the excavation may lead to surface problems. This is the reason why the characteristics of the mechanized tunneling methods, which use TBMs, and the geological and geotechnical properties of the formations, that are going to be excavated, and are related to the selection of the appropriate for the excavation machine, and the laboratory and in situ tests that take place to define them, are described in detail. The data, which has been collected from 72 boreholes along the tunnel alignment, include for the soil formations particle size analyses of the geomaterials, the liquid limit of the Atterberg limits, the plasticity index, the consistency index (in a few parts of the tunnel), the quality of the geomaterials, the SPT values and the permeability of the formations. For the rocky formations are presented the values of the GSI, the quality of the rock mass based on RQD values, the unconfined compression strength of the intact rock and the permeability of them. All of the above properties are presented also in figures where it becomes apparent how they develop along the tunnel alignment. From the data above the applicability of 4 TBM types, which include open face shield machines, rock TBMs, slurry shield TBMs and EPB machines, is described and the behavior of them versus the excavation is judged based on the geological and geotechnical conditions along the tunnel alignment.