Baugrundrisiken in schwierigem Untergrund mit geophysikalischen Methoden erkennen und entsch?rfen - am Beispiel des Neubaus der ARA Furnatsch in S-chanf, GR

摘要

During the excavation work for the ARA Furnatsch in S-chanf GR in summer 2017, a large open karst cave was found in the rock of the excavation pit consisting of gypsum-containing Raibter-Rauhwacke. It was to be expected that there would be further, invisible cavities under the excavation pit floor. Such cavities could pose a serious subsoil risk for the building structure. In order to test the bearing safety of the subsoil, it was measured area-wide by means of georadar. The investigation showed clear indications of several further cavities. Subsequently, an excavator was used to examine the identified areas. In fact, further karst cavities with expansions up to several tens of meters were uncovered. These were partly open, partly filled with fine-grained weathering products of the Rauhwacke. Before the floor slab was constructed, loose material was removed from the cavities and then filled with boulders, gravel and concrete.