ABSTRACT: Tunnelling through brittle fault zones requires special considerations during all phases of a tunnel project from design to construction. The geotechnical problems during construction relate primarily to the substantial heterogeneity of fault zones in terms of strength properties of the rock mass. Geotechnical aspects of fault characterization and problems of investigating a tunnel in a fault zone are discussed. It is demonstrated that a technical and economical optimization of construction can only be achieved by a flexible contractual setup which allows for modifications of the construction method. In this context it is emphasized that, based on a continuous evaluation of geological and geotechnical monitoring data, the predicted geological model is adjusted to the actual conditions. Based on the updated model, excavation and support is adjusted accordingly. The principal geotechnical difficulties and adequate counter measures during excavation problems related to tunnelling in brittle faults and the development of advanced support technology are demonstrated by case studies.

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