Applicability of hypoplasticity to reconstituted peat from drained triaxial tests

Proper understanding of the deviatoric behaviour of peats represents a challenge in soil mechanics. Exceptional high compressibility together with extremely high friction angles distinguishes peats from classical organic soils. Considerable amount of triaxial test data on peats can be found in the literature, mostly coming from standard undrained triaxial compression tests. However, only a minor part was intended to describe their prefailure behaviour. Also, limiting the investigation to the undrained response reduces the information on those ingredients of constitutive models, which are necessary to describe the deformational behaviour. This contribution aims to provide better insight into the prefailure deformational behaviour of peats, by analysing in detail the results of non-standard drained tests at various stress paths and undrained tests performed on reconstituted peat samples. Based on the experimental findings, an existing hypoplastic model, originally developed for fine-grained soils, has been adapted to capture the behaviour of peats. The model is directly calibrated on selected experimental results and validated on a variety of different stress path tests. The results reveal the merits of hypoplasticity in modelling the nonlinearity of the prefailure behaviour and the directional response of peats, which both are of great importance when assessing the serviceability limit states of geotechnical structures founded on peats.