Spectral Analysis of the Response of Coarse Granular Material to Dynamic Penetration Test Modelled with DEM

Abstract

Dynamic penetration tests are often used to determine the strength properties of surface soils. The paper presents a study on the use of spectral analysis on dynamic cone penetration tests results, modelled with discrete element method. This method is applied to assess the effect of the variation of the grain size distribution of the soil on test results. A two-dimensional discrete model is used to reproduce cone penetration tests in dynamic conditions: the tip of the penetrometer is driven in the material by successive impacts of a hammer on the penetrometer. For each impact of the hammer, a curve of the load applied by the tip on the soil is obtained versus the penetration distance of the tip. The curves of the load versus penetration traditionally used to calculate the tip resistance of the soil are analyzed with discrete Fourier transform in order to investigate curve’s shape. The effect of the variation of the grain size distribution of the soil on these curves is investigated, i.e. average particle diameter and span of particle size distribution. It was found out that the grain size distribution influences tip resistance but also the shape and oscillation modes of the curve of the stress–penetration curve. Based on these indicators, the exploitation of the load–displacement curve obtained with dynamic penetration tests could be enlarged to determine other properties of the soils.