Abstract

Most published research on CPT based SBT classification is on mineral soils. Consequently, these classifications do not accurately capture the classification of soft organic clays and peats. Organic soft soils are frequently present within the Holocene deposits in the Netherlands and in other deltaic areas worldwide. Organic soils can be identified by a specific combination of CPT parameters such as a high friction ratio, low cone resistance and low pore pressure response. In contrast to other soft soils, the strength is not necessarily low. This paper presents an updated CPT based classification with focus on organic soils, for the non-normalized SBT chart (Robertson, 2010, Lengkeek et al, 2022) as well as a new classification based on the stress normalized SBT chart (Robertson, 2016). In the new proposed classifications, additional boundaries are set based on the CPT pore pressure measurements, as this appears to be successful to separate organic soils from mineral soils. The performance of the classifications can be quantified by metrics such as the F1 score. The F1 score of the new proposed classifications all show significant improvement.