Medusa SDMT testing at the Onsøy Geo-Test Site, Norway

The Medusa SDMT is the last-generation, fully automated version of the seismic dilatometer (SDMT). An extensive in situ testing campaign with the Medusa SDMT was carried out in June 2022 in different soil types at four well-known benchmark test sites in Norway, part of the Geo-Test Sites (NGTS) research infrastructure managed by the Norwegian Geotechnical Institute. The experimental campaign was conducted as part of the Transnational Access project - JELLYFISh funded by H2020-GEOLAB. This paper presents a preliminary assessment of significant results obtained by Medusa SDMT at the Onsoy test site, a soft marine clay. The data is compared to available in situ and laboratory data previously published at the Onsoy test site. The results show that the Medusa SDMT data are consistent with traditional (pneumatic) SDMT results. Furthermore, the parameters obtained from the interpretation of Medusa SDMT data, in particular the overconsolidation ratio OCR, the coefficient of earth pressure at rest K-0, and the undrained shear strength su agree generally well with the corresponding parameters obtained in past investigations from other in situ and laboratory tests.