A virtual calibration chamber was built using a threedimensional model based on the discrete-element method. The chamber was then filled with a scaled granular\ud equivalent of Ticino sand, the material properties of which were selected by curve-fitting triaxial tests. Cone penetration tests were then performed under different\ud initial densities and isotropic stresses. Penetration resistance in the virtual calibration chamber was affected by the same cone/chamber size effect that affects physical calibration chambers and was corrected accordingly. The corrected cone resistance obtained from the virtual calibration chamber cone penetration tests shows good quantitative agreement with correlations that summarise previous physical results.Peer ReviewedPostprint (published version

A virtual calibration chamber was developed using a three-dimensional (3D) discrete element method (DEM) to perform cone penetration tests (CPTs) on a discrete analogue of Ticino sand. The macroscale response of the DEM model was previously shown to be in good quantitative agreement with that of analogous physical models. In the current study the performance of the model at meso and microscale levels of resolution is examined. The microscale response is examined using particle displacements and contact force distributions. The mesoscale behaviour is examined using stress and strain fields obtained through appropriate averaging and interpolating procedures. Four CPTs are examined at the steady-state penetration stage. The effects of radial boundary conditions, initial stress state, initial average density, and particle rotational inertia are examined. The ability of the micro and mesoscale data to identify and explain the relevant mechanisms underlying the significant differences in the macroscale response of the models is discussed. Comparisons with similar phenomena observed in physical tests are also highlighted.Peer ReviewedPostprint (published version

A three-dimensional discrete element model is used to investigate the effect of grain crushing on the tip resistance measured by cone penetration tests (CPT) in calibration chambers. To do that a discrete analogue of pumice sand, a very crushable microporous granular material, is created. The particles of the discrete model are endowed with size-dependent internal porosity and crushing resistance. A simplified Hertz-Mindlin elasto-frictional model is used for contact interaction. The model has 6 material parameters that are calibrated using one oedometer test and analogies with similar geomaterials. The calibration is validated reproducing other element tests. To fill a calibration chamber capable of containing a realistic sized CPT the discrete analogue is up-scaled by a factor of 25. CPT is then performed at two different densities and three different confinement pressures. Cone tip resistance in the crushable material is practically insensitive to initial density, as had been observed in previous physical experiments. The same CPT series is repeated but now particle crushing is disabled. The ratios of cone tip resistance between the two types of simulation are in good agreement with previous experimental comparisons of hard and crushable soils. Microscale exploration of the models indicates that crushing disrupts the buttressing effect of chamber walls on the cone. A three-dimensional discrete element model is used to investigate the effect of grain 6 crushing on the tip resistance measured by cone penetration tests (CPT) in calibration 7 chambers. To do that a discrete analogue of pumice sand, a very crushable microporous 8 granular material, is created. The particles of the discrete model are endowed with size-9 dependent internal porosity and crushing resistance. A simplified Hertz-Mindlin elasto-10 frictional model is used for contact interaction. The model has 6 material parameters that are 11 calibrated using one oedometer test and analogies with similar geomaterials. The calibration 12 is validated reproducing other element tests. To fill a calibration chamber capable of 13 containing a realistic sized CPT the discrete analogue is up-scaled by a factor of 25. CPT is 14 then performed at two different densities and three different confinement pressures. Cone tip 15 resistance in the crushable material is practically insensitive to initial density, as had been 16 observed in previous physical experiments. The same CPT series is repeated but now particle 17 crushing is disabled. The ratios of cone tip resistance between the two types of simulation are 18 in good agreement with previous experimental comparisons of hard and crushable soils. 19Microscale exploration of the models indicates that crushing disrupts the buttressing effect of 20 chamber walls on the cone. 21 KEY WORDS: 22Discrete element method, pumice sand, cone penetration, particle crushing, double porosity 23 *Manuscript Click here to view linked References 2 2

International audienceIn this paper the development and experimental validation of a numerical model of two-dimensional unsaturated flow in a double-porosity medium is presented. The model is based on the coupled formulation for flow in macro- and micropores obtained by homogenization. It was applied to simulate the axisymmetrical tension disk infiltration experiments that were carried out in a double-porosity medium. The physical model was a three-dimensional periodic structure, composed of porous spheres made of sintered clay and embedded in Hostun fine sand HN38. The hydraulic parameters of both porous materials were determined by inverse analysis of independent infiltration experiments performed on sand and sintered clay. The effective parameters of the double-porosity medium were calculated from the solution of the local boundary value problem, obtained from the homogenization procedure. The cumulative infiltration curve and the global dimensions of the humidified zone obtained from the numerical solution are in good agreement with the observations. Moreover, numerical simulations showed the existence of a narrow zone of local nonequilibrium that moves with the infiltration front. Upstream of this zone, the infiltration bulb is in the local equilibrium conditions