Sand Grain-size Analysis Using a Laser Diffraction Analyzer

Abstract

Grain size analysis is a fundamental tool for examining sediments and classifying coastal environments. The traditional sieve method is, however, a laborious task, and a laser diffraction method is widely adapted recently. In this study a comparison of grain size data between the OASIS laser diffraction and sieve method was conducted. After precisely sieving a natural beach sand at the interval of 0.25 phi, four different fractions (0.75-1 phi, 1.75-2 phi, 2.75-3 phi and 3.75-4 phi) were selected for test. Each fraction sample was OASIS-measured four times, and the results show good precision with a range of 0.008 to 0.020 phi in standard deviation. In the cases of mixed samples of two selected fractions with various mixing ratios (1:9, 3:7, 5:5, 7:3 and 9:1), size data by the laser diffraction analyzer resolve the original modes well. However, mixed samples having less than 10 % coarse-grained component, the grain-size distributions show noticeable deviation from those expected. a comparison of grain size data between the OASIS laser diffraction and sieve method was conducted. After precisely sieving a natural beach sand at the interval of 0.25 phi, four different fractions (0.75-1 phi, 1.75-2 phi, 2.75-3 phi and 3.75-4 phi) were selected for test. Each fraction sample was OASIS-measured four times, and the results show good precision with a range of 0.008 to 0.020 phi in standard deviation. In the cases of mixed samples of two selected fractions with various mixing ratios (1:9, 3:7, 5:5, 7:3 and 9:1), size data by the laser diffraction analyzer resolve the original modes well. However, mixed samples having less than 10 % coarse-grained component, the grain-size distributions show noticeable deviation from those expected.