RATE EFFECTS ON THE STRESS-STRAIN BEHAVIOUR OF EPS GEOFOAM

SOILS AND FOUNDATIONS

SHOHEI KAWABE¹  YOSHIMICHI TSUKAMOTO¹  FUMIO TATSUOKA¹  G. E. ABDELRAHMAN² 

[1] Department of Civil Engineering, Tokyo University of Science;Civil Engineering Department, Fayoum University

关键词: creep deformation;    elasto-viscoplastic model;    EPS geofoam;    loading rate effect;    non-linear three component model;    unconfined compression test;    viscous properties;    (IGC: D5/D6);   

DOI  :  10.3208/sandf.48.479

学科分类：建筑学

来源: Japanese Geotechnical Society / Jiban Kogakkai

【 摘 要 】

References(30)The rate-dependency of the stress-strain behavior of EPS (Expanded Polystyrene) geofoam with densities of 19.3 and 28.0 kg/m3 was investigated by performing unconventional unconfined compression tests. A set of monotonic loading (ML) tests were performed at different constant values of vertical (axial) strain rate, εv. The εv value was stepwise changed many times and several sustained loading (SL) tests were performed during otherwise ML at a constant εv in other tests. A number of SL tests were performed during global unload and reload cycles to infer the stress-strain relation when εv=0. The elastic properties were evaluated by applying minute unload/reload cycles during otherwise ML. The rate-dependent stress-strain behaviour observed in these tests was described by an elasto-viscoplastic model (i.e., a non-linear three-component model), for which the vertical (axial) stress, σv, consists of inviscid and viscous components, σvf and σvv, while εv consists of elastic and irreversible components, εve and εvir. It is shown that the viscous property of EPS geofoam is of Isotach type in that, under the loading conditions where εvir is always positive, the current σvv value is a unique function of instantaneous εvir and εvir, therefore the strength increases with εv. This viscous property was quantified based on the test results and incorporated into the model. The rate-dependent stress-strain behaviour, including the creep behaviour, observed in the experiment is simulated very well by the proposed model. In particular, the fact that the creep strain becomes significant when the sustained σv value becomes larger than the inviscid yield vertical stress is well simulated.

【 授权许可】

Unknown