It is quite unusual to consider the exploitation of geothermal resources during at the tunnel design stage. This paper is intended to analyse the nature and the potential of the geothermal resources. These are essentially the hot or cold water inflow and the temperature of the surrounding ground itself. A methodological approach is proposed to face the problem, determine relevant information and estimate the attractiveness of the application. The approach is then applied to the case study of

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... metro line Dudullu-Bostanci in Istanbul, currently under design, by identifying a possible application of heat exchangers integrated into the tunnel lining and evaluating preliminarily the environmental and economical aspects.