An equation to represent grain-size distribution: Reply

• Published in: Canadian geotechnical journal Vol. 39; no. 6; pp. 1437 - 1438
• Main Authors: Fredlund, M D, Fredlund, D G, Wilson, G W
• Format: Journal Article
• Language: English
• Published: Ottawa, Canada NRC Research Press 01.12.2002; Canadian Science Publishing NRC Research Press
• Subjects: Hansen, David; Soil mechanics
• ISSN: 0008-3674; 1208-6010
• DOI: 10.1139/t02-080

The authors wish to thank the discusser for putting together his case for the possibility of using a log-normal type representation to characterize particle size distributions. Log-normal type plots have found a degree of acceptability in the area of hydrology; however, similar attempts to use log-normal distributions have not been met with the same enthusiasm in the soil mechanics discipline. Geotechnical engineers do not view particle size distribution as statistical or probability-based information related to the number of particles associated with each particle size range. In the original paper, the authors point out that 'Gardner (1956) proposed a two-parameter, log-normal distribution to provide representation of grain-size distribution data.' The idea of using log-normal distributions to characterize grain-size distribution curves has been around for a long time. It does not appear to have gained significant acceptability in geotechnical engineering nor engendered further research interest. It was against this background that the present research study was formulated. It was decided to further investigate the use of an empirical, mathematically based equation where the fitting parameters had some physical meaning. The equations were focused on the generally accepted 'percent passing' versus the logarithm of the particle size plots.