Permeability of Mud Mountain Dam Core Material

During the early investigation of the material contemplated for use in the impervious core of the Mud Mountain Dam (in a northwestern state), it as proved that the moisture content of the material when compacted had a much greater influence on the permeability than did the density of the material, within the range of densities at which it would be compacted during construction. Since the voids in the soil act as conduits for the water, it is postulated that the water content of the soil at the time of compaction governed the arrangement of the voids. At a high water content, the voids were apparently all of uniformly small size and the permeability was low. At a low water content, but at the same numerical void ratio or density, the voids were apparently of a wide range of sizes and the permeability was high. Thus, a wide or narrow range in void sizes may be likened to a wide or narrow range in particle sizes.