The prediction quality of three of the most sophisticated constitutive models for sands has been examined based on a comparison of results from element test simulations and laboratory tests. Hypoplasticity with intergranular strain, the Sanisand elastoplastic model in the version of 2004 and the recently proposed ISA (intergranular strain anisotropy) model have been inspected. The laboratory tests performed on Karlsruhe fine sand used in the present study are freely available on the homepage of the first author. The model predictions have been inspected for drained and undrained monotonic triaxial tests with various densities and pressures and for monotonic tests with a few number of un- and reloading cycles. The main focus, however, lies on undrained cyclic triaxial tests with either stress or strain control and with different densities, initial stresses and stress/ strain amplitudes. The strengths and weaknesses of the different constitutive models for various test conditions are worked out.

Introduction

Numerical simulations of geotechnical structures under earthquake loading, which may eventually be affected by soil liquefaction, require the use of sophisticated constitutive models for the soil. For these analyses, the selected constitutive model is expected to reproduce the mechanical behavior of the soil at different stress/strain amplitudes, especially under undrained cyclic loading, whereby cyclic mobility effects and the accumulation of pore water pressure should be adequately described. Several advanced constitutive models for non-cohesive soils have been developed during the last two decades, e.g. the hypoplastic model with intergranular strain [20,22], the Sanisand elastoplastic model [3,4], or most recently the ISA (intergranular strain anisotropy) model [7]. Likewise, a huge number of high-quality laboratory tests with various boundary conditions and control has been performed by the authors at the Institute of Soil Mechanics and Rock Mechanics (IBF) at Karlsruhe Institute of Technology (KIT) during the last decade. The experimental database has been published in Refs. [25,26] and made freely available on the homepage of the first author [24]. The data enable the calibration, inspection and further development of constitutive models for granular materials, considering as many different boundary conditions and types of control as possible. Such close examination of the constitutive equations based on element tests creates confidence for an application of the model to different real problems.