  Uniform and multi-dispersed grain packs have been frequently used to
conceptually study flow in porous media. Numerical simulations were previously
used to address the effect of particle shape on characteristics, such as pore
space fractal dimension, moisture characteristic curve (MCC) and saturated
hydraulic conductivity (SHC) of grain packs. However, experimental observations
are still required since fractal-based approaches have been extensively
proposed to model various properties in porous media. In this study, 16 angular
sand and 16 spherical glass bead samples with different particle size
distributions (PSDs) from well- to poorly-sorted were packed. The MCC was
measured using the combination of sandbox and pressure plates methods. The pore
space fractal dimension (DMCC), calculated from the measured MCC, ranged from
0.80 to 2.86 in sand and from -0.18 to 2.81 in glass bead packs, which
indicated that DMCC may be negative in homogenous media (e.g., glass bead
packs) consistent with several studies in the literature. Results showed
greater DMCC for the sand packs than the glass bead packs with the same
geometric mean diameter values and PSDs. This clearly demonstrated the effect
of particle shape on DMCC in the studied packs. The critical path analysis
(CPA) approach was used to estimate the SHC measured using the constant-head
method. We found that the CPA estimated the SHC accurately, within a factor of
four of the measurements on average. Although the CPA is theoretically known to
be accurate in media with broad pore size distributions, we experimentally
found that it estimated the SHC in various types of grain packs reasonably
well.
