Structural analysis along 24 cross sections crosscutting several windows in the central Hellenides provides the sense of nappe movements as well as the location of destroyed oceans lying between the Apulian and Eurasian continents from the Mesozoic. Orogeny took place in two phases: The first phase, “the Eo‐Hellenic” phase, was initiated by convergence of the Apulian and Pelagonian plates with west directed subduction and closure of the Pindos Ocean. Late Jurassic obduction of oceanic lithosphere over the western margin of the Pelagonian plate was followed by footwall imbrication, mylonites and sheath folds. During the late Cretaceous, uplift was associated with ductile normal faulting at depth and tectonic unroofing at shallow crustal levels. The second phase, “the Meso‐Hellenic” phase, comprised the closure of the Ambelakia Ocean at the eastern margin of the Pelagonian plate and continental subduction along the eastern margin of the Apulian plate. West directed subduction of the Ambelakia Ocean was associated with eastward directed ductile thrusting, folding and blueschist metamorphism. Blueschist formed within a simple duplex structure at depth and was subsequently overthrusted in the late Eocene onto the Olympos microcontinent, which acted as a major obstacle to the eastward directed nappe movements. Up to 150‐m‐thick cataclasites, kink folds and a spaced cleavage were formed during the late stage of the continental collision. “A subduction” along the eastern margin of the Apulian plate caused kink folding and reimbrication of the western parts of the Pelagonian basement. Since the Oligocene, the overthickened crust collapsed by means of low‐angle normal faults.
Field instrumentation was used in the construction of two twin tunnels for the new Egnatia Motorway in Greece. This paper describes the displacement monitoring results taken during tunnelling through heavily fragmented limestone varying from a block size >10 cm down to sandy gravel and sandy silt or gouge. The primary lining displacements monitored by surveying methods appear to be directly related to the detailed geological subdivisions of the limestone observed at the tunnel face. Maximum values of settlement were recorded during tunnelling through the gouge and reached 80 mm, while horizontal movements up to 40 mm were recorded associated with outward deflection of the support frames. The development of settlement with time shows that settlement of the tunnel crown and sides increased sharply while the face of the tunnel was within a tunnel diameter of the station point under consideration and reached equilibrium when the excavation face was at least 3 to 4 tunnel diameters beyond it. Surface settlements above the axis of the tunnel were first observed when the face of the tunnel was directly beneath the station. At the entrance portals of the tunnels the limestone overlies a thin sedimentary clay formation and gypsum. Horizontal movements along the interface between the limestone and the underlying clay sequence as well as within a clay/gypsum layer at the portals were observed using a standard inclinometer.
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