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Abstract

To increase safety and reduce costs during the drilling process and the maintenance of the tunnels, a detailed geotechnical exploration is necessary. To meet this goal, new technologies have been developed that can be integrated into the tunnel boring machine (TBM) or the conventional drill-andblast method. Especially high-resolution seismic measurements have got the potential to provide essential information about the mechanical stability of the tunnel wall and face in a fast and nondestructive way. These methods enable us to explore the rock mass in front of the tunnel face and map existing tunnel walls with relatively small effort. In this framework, hardware and software components 334 - Umwelt- und Ingenieurgeophysik - Allgemeine Themen for the exploration of underground constructions have been developed at the GFZ. Potentially risky sectors can thus be identified before damage occurs; however, futher research is needed to achieve a sound and reliable high-resolution imaging of the structures. The collaborative project SOUND therefore focuses on three main topics that build upon a common basis of acquisition and interpretation techniques: (1) Seismic exploration during tunnel excavation, using the cutter head of the tunnel-boring machine as a seismic source leading to a high spatial coverage of source signals, (2) Investigation of the acquired data by 3-D elastic Finite-Difference modelling, traveltime and full waveform tomography as well as (3) Enhancement of the seismic sources developed in previous projects for long-term monitoring. These sources shall allow for broad-band signal generation and high signal repeatability and have been tested in the UndergroundLab of the GFZ in the research mine "Reiche Zeche" in Freiberg over 8 month in 2011. Concomittantly to the measurments, an adit was excavated in the UndergoundLab. Premliminary results of these measurments showed an excellent repeatability of the signals. The coda wave portion of the signals varied in the way that the similarity of the signal decreased over time. This was interpreted as an effect caused by changes in the rock induced by the continuous excavation of the adit.