Construction of Paramithia tunnels, Egnatia motorway, Greece

Abstract

The paper describes in detail the construction process followed for site set-up, portal formation, tunnel excavation and primary lining of two tunnels in the presence of heavily fragmented cataclastic material. Excavation techniques used to secure the crown of the tunnel and to avoid extensive collapses included, inter alia, grouted forepoles of various types and density, down the hole drilling, the use of self-drilling anchors and fibre-reinforced shotcrete. The optimum set of measures was selected according to block size, interlocking of blocks and cohesion of each unit at the tunnel crown and sides. Attention is paid to the observational method applied, the treatment of special cases with novel techniques such as horizontal cement piles and the treatment of localised ground collapses, and to the production rates achieved during construction. A procedure applicable when mixed conditions at the tunnel face are encountered during excavation in tunnelling projects is proposed.