Kazuwo Imai

Simulated effect of box size and wall on porosity of random packings of spherical particles

SummaryEffects of the size of the box which spherical particles are deposited into on the porosity of a resulting particle aggregate have been simulated and examined, particularly to find out if the extrapolation method often used by experimenters is certainly right; this method is based on the empirical fact that the porosity is inversely proportional to the box size. The simulation justified the inverse proportionality and demonstrated that the porosity obtained by the simulated extrapolation coincides with that by the simulation with use of conventional cyclic boundary conditions. This coincidence implies the extrapolation gives the right experimental results of porosities and also that the conventional cyclic boundary condition method is a really strong method to construct a random packing of “infinite” extent by simulation. An effect of the box wall has also been explored in view of area porosisties and cumulative distribution of diameters of circles appearing on aggregate cross-sections. Furthermore, slopes of the straight line of the porosity versus ratio of the particle diameter to the box size have been discussed in terms of two statistical geometry models.

Simulated Effective Elastic Moduli and Wave Velocities in Water-Saturated Sintered Glass-Beads

SummaryEffective elastic moduli of sintered glass-beads and wave phase velocities in this sintered material saturated by water are estimated by a computer simulation. The simulation consists of (A) simulated random packing of equal spheres, (B) FEM estimation of the spring constants of 6 degrees of freedom for a “sintered” pair of spheres, and (C) simulated tensile tests of a “random network”, as a model of sintered glass-beads, of springs with the estimated spring constants; these tests yield the effective elastic moduli of sintered spherical particle aggregates. And (D) use of these moduli in Biots simplified formulae gives phase velocities for the first compressional and shear bulk waves. Results of the simulation are compared with the estimates based on the self-consistent models and those by experiments. The simulated results are in good agreement with the experimental ones.

Mechanical response of a water-saturated core sample under opposite diametrical loadings

SummaryBy use of the theory of poroelasticity, the analytical solutions were obtained for mechanical responses of a water-saturated core sample subjected to opposite diametrical loadings that vary like a step function of time (Problem I) and a linearly increasing function of time (Problem II). These loadings correspond to elastic moduli tests (by Hondros) and indirect tensile strength tests (the Brazilian tests) of dry brittle materials, respectively. The analysis showed how the diffusion of pore fluid affects these tests, if the tests are carried out for fluid-saturated samples. Furthermore, the accuracy of the Stehfest numerical Laplace inversion was checked based on the analysis. In addition, a method of determining poroelastic moduli was proposed.