Drop-ball arrangement for centrifuge experiments

Abstract

The study of soils or structures under dynamic loadings is a promising field of centrifuge scale experiments. The proposed drop-ball arrangement generates a short duration loading wave using a spherical ball falling on the soil surface during the centrifuge flight. The excitation is of transient type and the wave reflections are precisely controlled. The tridimensional accelerometers completely determine the acceleration vectors in terms of direction and amplitude. The elimination of reflected waves by homomorphic filtering is a good alternative to isolation techniques. Filtering or wavelet methods, associated with envelope curves calculation (Hilbert transformation), give phase and group delays at different frequencies. The different propagation parameters (dispersion laws, attenuation, wave length…) can be evaluated with a mechanical behaviour model and compared with the experimental results. In this study, spherical wave field analysis assuming linear viscoelasticity gives a complete analytical description of propagation.