Overbreak Risk Assessment in the Athens Metro TBM Tunnels

Assessment of TBM tunneling conditions and potential for damage in building and archaeological remains is of greatest benefit in resolving problems associated with the construction of the Athens Metro, Greece. In this predictive philosoply an overbreak risk assessment method was developed based on intuitive simplicity, theoretical background and past experience. The method evaluates ground conditions from boreholes and defines risk on the basis of hazard severity and likelihood of occurrence. As the method proved macroscopically efficient, research on the subject is ongoing with evaluation of monitoring data gathered during construction and back analyses using numerical techniques.