A methodology for assessing geotechnical hazards for TBM tunnelling - illustrated by the Athens Metro, Greece

Unexpected ground conditions have always been a major problem for the tunnelling industry. As demand for the development of new underground structures, regardless of the ground conditions, has increased, safety and risk considerations have become even more important. The methodology presented in this paper aims at the identification of risk-prone areas, incorporating, at the same time, the uncertainty of ground conditions. It is focused on TBM tunnelling and can be implemented in the early stages of the project. The methodology assesses the hazards by introducing the concept of a vulnerability index, which is based on the principles of rock engineering systems, to identify the weighting of the parameters, and on probabilistic modelling to address the uncertainty in the parameters' values. The proposed model is illustrated via the Athens Metro case study, used also for validating its performance under actual construction conditions. (C) 2004 Elsevier Ltd. All rights reserved.