ABSTRACT
The performance of an EPB-TBM was studied in the Silurian-Lower Devonian aged Pelitli Formation consisting of siltstone and sandy limestone which was a part of the current Metro Project in Istanbul. The geology is complex and often cut by andesite dykes. These magmatic intrusions are high-strength rocks. However, contact zones or transition zones with the main rock are highly fractured and weathered. These zones are critical in mechanized tunneling which is liable to tunnel face instability, face collapses, or jamming of the cutterhead. TBM thrust force, torque, penetration, EPB face pressure, and specific energy values are carefully analyzed and compared when cutting the main rock, andesite dykes, and transition zones. The mean EPB face pressure being 0.9 bar was increased up to 2.5 bar in the weathered part of the dyke, which played a mitigation factor in eliminating the unfavorable characteristics of transition zones.
