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
