Estimation of Permeability for Sand and Gravel Based on Pore-Size Distribution Model

In this study, the author proposes two methods for estimating the permeability of sand and gravel from their pore structure. First, the author proposes a model to be used in both methods for estimating the pore-size distribution based on the concept of the probability of particles' contact with one another in consideration of the number of particles for different particle sizes calculated from the particle-size distribution. In one method, the author defines an index of the threshold pore size around which the cumulative pore size increases rapidly in the obtained pore-size distribution model. Then, a semiempirical formula is proposed for evaluating the permeability. Here, by taking the power of the threshold pore size as the key parameter, the relationship between permeability and threshold pore size can be expressed as a linear function. In the other method, the author proposes a theoretical formula for estimating the permeability from the Hagen-Poiseuille flow equation using the proposed pore-size distribution model. Comparison with test measurements demonstrates that the calculations obtained from the proposed methods using the pore-size distribution agreed well with the test measurements, whereas those obtained from the existing methods directly using the particle-size distribution did not.