Geotechnical characterization of soft soil deposits in Northern Poland

Abstract This paper presents a geotechnical characterization of deltaic soft soil deposits in the Vistula Marshlands, northern Poland. It shows the limited applicability of organic soil classifications based on Cone Penetration Tests (CPTU) and Dilatometer Tests (DMT). None of the in-situ-based classifications correctly identifies peat. Analysis of the behaviour of contractive/dilative soil layers according to Robertson's updated classification (2016) is shown to be in agreement with volumetric changes observed during triaxial compression tests. The coefficient of primary compression C c is found to decrease exponentially with the initial bulk density ( ρ d0 ) and to increase linearly with the in-situ water content ( w c ). The presented geotechnical characterization and reference data can be used for foundation design and soil improvement in the soft organic soils of northern Poland.