An experimental database for the development, calibration and verification of constitutive models for sand with focus to cyclic loading: part II—tests with strain cycles and combined loading
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For numerical studies of geotechnical structures under earthquake loading, aiming to examine a possible failure due to liquefaction, using a sophisticated constitutive model for the soil is indispensable. Such model must adequately describe the material response to a cyclic loading under constant volume (undrained) conditions, amongst others the relaxation of effective stress (pore pressure accumulation) or the effective stress loops repeatedly passed through after a sufficiently large number of cycles (cyclic mobility, stress attractors). The soil behaviour under undrained cyclic loading is manifold, depending on the initial conditions (e.g. density, fabric, effective mean pressure, stress ratio) and the load characteristics (e.g. amplitude of the cycles, application of stress or strain cycles). In order to develop, calibrate and verify a constitutive model with focus to undrained cyclic loading, the data from high-quality laboratory tests comprising a variety of initial conditions and load characteristics are necessary. It is the purpose of these two companion papers to provide such database collected for a fine sand. Part II concentrates on the undrained triaxial tests with strain cycles, where a large range of strain amplitudes has been studied. Furthermore, oedometric and isotropic compression tests as well as drained triaxial tests with un- and reloading cycles are discussed. A combined monotonic and cyclic loading has been also studied in undrained triaxial tests. All test data presented herein will be available from the homepage of the first author. As an example of the examination of an existing constitutive model, the experimental data are compared to element test simulations using hypoplasticity with intergranular strain.
KeywordsCombined monotonic and cyclic loading Cyclic triaxial tests Database Fine sand Isotropic compression tests Oedometric compression tests Strain cycles Un- and reloading cycles
Parts of the presented study have been performed within the framework of the project "Geotechnical robustness and self-healing of foundations of offshore wind power plants” funded by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU, project No. 0327618). Other parts were conducted within the framework of the project "Improvement of an accumulation model for high-cyclic loading" funded by German Research Council (DFG, project No. TR218/18-1 / WI3180/3-1). The authors are grateful to BMU and DFG for the financial support. All tests have been performed by the technicians H. Borowski, P. Gölz and N. Demiral in the IBF soil mechanics laboratory.
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