The dry-separation method is an alternative to the wet-preparation in the\ncurrent European Standard for the determination of particle size distributions\nby the sieving of soils. Due to the risk of error, dry-separation is cautioned\nagainst in the standard; however, there is no additional guidance as to when it\nis unsuitable nor for the magnitude of error that it may introduce. This study\ninvestigates the dry-separation method as an alternative by comparing with\nthe conventional method of Wet-preparation in terms of particle-size distributions\nof eight cohesionless sand-gravel soils with varying amounts of\nnonplastic fines. The findings indicate a gradually increasing sieving error\nfor fractions at minus 0.5 mm with the amount of fines in the soil, and depending\non the fines content of the soil, dry-separation introduced errors\nupwards of 45% in silt-sand-gravel soils. An empirical best-fit formula is\nproposed for the estimation of the error using the dry-preparation method\non this type of soil. Furthermore, to avoid sieving errors, the results suggest\nthat the dry-separation method should not be used for silt-sand-gravel soils\nexceeding 2% silt size fractions.
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