An investigation has been made of the relations among porosity, permeability, and texture of artificially mixed and packed sand, to determine the approximate porosity and permeability values to be expected for unconsolidated sand of eight grain-size subclasses and six sorting groups. The sand samples were prepared so that the weight fractions were distributed normally about the median grain size. Porosity values were determined for two packings, designated as “dry-loose” and “wet-packed.” Porosity data for “wet-packed” sand samples remain about the same for changes in grain size of a given sorting, but decrease from an average of 42.4 percent for extremely well-sorted sand to 27.9 percent for very poorly sorted sand. These experimental data agree within 5 porosity percent with framework porosity values obtained for natural packing of 25 Holocene barrier-Island sand samples of a limited size-sorting range, and appear to be representative of minimum porosities expected for natural packing of most unconsolidated, clay-free sand.
The 48 artificially mixed and wet-packed experimental sands selected for porosity measurement also were used to determine permeability. Inasmuch as there are some irregularities in the experimental data caused by the inability to pack each sample uniformly, an average adjusted permeability value has been calculated. The average adjusted permeability values become progressively lower with decreasing grain size and poorer sorting, and agree well with permeability values computed by the Krumbein and Monk formula for most grain-size and sorting classes.
Reference photographs or visual textural comparators enable a rapid estimation of grain shape, roundness, size, and sorting. Grain-size-sorting comparators, representing photomicrographs of thin sections of the porosity and permeability test samples, are especially useful in estimating original textural parameters form thin sections of severely compacted and silica-cemented sandstones.