A through pilot bore is produced with a bore head guided in the bore path along the planned tunnel course. Samples are removed from the pilot bore for geo-physical examination. The pilot bore is produced along the centre line of the planned tunnel course. In the production of the pilot bore, bore advance parameters are highlighted, which can then be related to the bore hole investigation. One or more of the following bore advance parameters are established: bore pressure, advance speed, abrasion of the bore head. Samples are taken from the flushing back flow of the pilot boring. Pre-investigation is enacted by geo-physical depth probing of the surface.
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