Dry Sieving (particle-size of sand fraction)

Objectives

  • To quantitatively determine the particle size distribution of the sand fraction (0.063 –2mm) using a dry sieving method.

  • To qualitatively describe the nature of the gravel fraction (>2mm)

Equipment and Reagents

Vibratory sieve-shaking machine with timer

Two nests of sieves, 0.063 – 2mm at 0.5 phi intervals (see Wentworth scale)

Stiff sieve brush

Balance with tare facility, accuracy + 0.5 g, used with a paper plate receptor.

Temperature-controlled oven, preset to 105oC + 5

Paper plates

Large sheet of thin card.

Log sheets

Methodology

  1. Dry the sample(s) in the oven at 105oC for half a day.

  2. Record the total weight of sediment sample to be sieved.

  3. Ensure the nest of sieves is in the correct order.

  4. Add the sample to the top of the nest.

  5. Clamp the nest into the shaker. Sieve for 20 minutes. NOTE: Prepare a second sample for sieving with a second nest (2-4 above). When the first nest is ready put the second nest onto the shaker and start the next 20 minute cycle. Always have one sample sieving while another is being weighed.

  6. Weigh the first set of sieves, from the top down. Invert each over the sheet of card, brush the mesh clean, from both sides. Use the card as a chute to direct the sand onto the balance receptor. Record the weight retained on each sieve. The contents of each sieve are re-amalgamated into a single sample after weighing.

  7. Describe the nature of the material retained on the 2mm sieves (typical and maximum dimensions, lithogenic or biogenic origin, level of encrustation …. etc).

  8. The sample is stored in a labelled plastic bag after sieving.

  9. The data from the log sheet is entered into an EXCEL programme, and the checksums noted and the form of the graph checked as a quality assurance procedure.

NOTE 1: This methodology is based on British Standard 1377.

NOTE 2: For large volume samples, the particle-size of the gravel fraction (up to 16mm diameter) can be determined using the same method, by adding sieves to the top of the nest.