Compression behaviour of reconstituted organic soils: Effect of sample preparation and organic content

¹ Chair of Soil Mechanics and Geotechnical Engineering, Technische Universität Berlin, Berlin, Germany
² Chair of Soil Mechanics, Foundation Engineering and Environmental Geotechnics, Ruhr-Universität Bochum, Bochum, Germany

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Organic soils are considered problematic in geotechnical engineering due to their low bearing capacity and high compressibility. Since field samples usually exhibit great heterogeneity, the use of reconstituted samples provides a reasonable alternative for systematic investigations. Hence, oedometer tests on reconstituted organic soils composed of peat and kaolin at varying proportions were conducted to investigate the effect of sample preparation and organic content on the compression behaviour. Different preparation methods were used: moist peat in one case and dried peat with added water in the other. Previous studies have shown that the compression behaviour of organic soils is strongly influenced by prior drying and re-saturation. The reason given for this is the change in structure as a result of drying. Initial tests at both institutions confirm these results. The duration of the compression phases differed markedly, with samples prepared from dry peat showing a shorter primary compression phase and an increased creep rate, indicating tertiary compression. Additional oedometer tests confirmed that pure clay does not exhibit tertiary compression, whereas the creep rate increased with higher peat content. Performed statistical evaluations reveal correlations between oedometric parameters, void ratio, and organic content, which are consistent with previously proposed equations for natural peats.