Geo-engineering properties of Eemian peats from Radzymin (central Poland) in the light of static cone penetration and dilatometer tests

- Fibrous, diagenetized peats show very high mechanical parameter values.
- CPT/DMT nomograms do not always allow for the proper identification of a fibrous peat.
- Eodiagenetic processes radically limit the interpretation of preconsolidation parameters.
- Diagenetic processes extend the variability of mechanical parameters.

The paper presents the results of field studies testing the reaction of Eemian peats on the mechanical effect of standard measurement tools (CPT/CPTU, Marchetti dilatometer). Based on the collected undisturbed samples, macroscopic observations were made and SEM observations were conducted to identify the microstructural features. A fibrous structure and advanced diagenetic changes have been noted in the studied peats despite their relatively young age. These may have resulted from an exceedingly strong structural reinforcement, which causes that the studied sediments cannot be treated as low-bearing soils. Diagenetic processes caused farfetched changes of the mechanical properties, which is reflected e.g. in classification normograms. Standardized diagrams may lead to false conclusions. The presented studies of organic soils are an example of strong influence of structural features and diagenetic phenomena on the results obtained for native soils. At the same time, they imply particular caution in the interpretation of the substratum properties based only on the commonly used in situ tests. The values and variability of the collected parameters have been presented as frequency distributions. Additionally, the apparent character of the properties of preconsolidation parameters (OCR) has been shown.