Geotechnical characterization and strain-rate dependent response of peat from the Netherlands

For construction and maintenance of infrastructure, a good understanding of the engineering properties of the subsoil is needed. In some areas, the subsoil contains deposits of peats and organic soils. Although many studies on the strength of peats, in the laboratory and the field, have been published, little is known on the strain-rate dependency of peat strength. In this paper, we discuss a series of triaxial and direct simple shear (DSS) tests conducted at different strain rates. The results were compared to trends observed in clays. Moreover, numerical simulations were conducted using the Creep SClay1 model. Equivalent to clay behaviour, the tested peat showed the impact of rate effects. The higher the shearing rate, the higher the undrained shear strength. The numerical simulations captured the peat behaviour reasonably well. Moreover, heterogeneity of the tested material masked a possible trend with over-consolidation ratio (OCR). The tests provided a clear starting point for further exploring rate effects in testing peats. Additional tests and numerical simulations by different constitutive models that account for viscous effects are suggested to develop an understanding of peat behaviour.