A coupled numerical-experimental approach for bender-based G0 measurements in geomaterials

Abstract

Bender elements are shear wave transducers, used for the experimental identification of the small-strain shear moduli of geomaterials. They offer good coupling with the sample and controllable loading signal and frequency, but the interpretation of their readings poses considerable difficulties. This study lays the foundations for a coupled, numerical-experimental approach to this issue, using hybrid-Trefftz finite elements to model the bender element experiment. Two main reasons justify the choice of these elements. First, they are much less wavelength-sensitive than conventional finite elements, meaning that coarse meshes can be used to model waves of very different types and frequencies. Second, hybrid-Trefftz elements use physically meaningful approximation bases. This enables the numerical filtration of the spurious waves from the response of the sample. The elements recover adequately the output signal obtained experimentally, for multiple laboratorial setups. The numerical filtration of the compression waves endorses the clear identification of the shear wave arrival.