Determining Dry Density of Soil Using Water Displacement Technique

The method employed for assessing the dry density of soil is the water displacement test. This technique proves especially effective in evaluating the in-place dry density of cohesive soil, given the required specimen characteristics.

Sample Preparation

Commencing the process involves trimming the soil sample to achieve a consistent shape. To make the specimen impervious to water, a coating is applied. The total volume of the waxed specimen is then determined by measuring the water displaced by the specimen.

Apparatus

The following apparatus is necessary for the procedure:

  1. Water Displacement Apparatus
  2. Weighing Balance (Accuracy: 1g)
  3. Paraffin Wax (Density: 0.91 g/ml)
  4. Cutting Knife
  5. Heater
  6. Oven
  7. Measuring Jar
  8. Brush
  9. Water Content Container

Procedure

  1. Specimen Preparation: Take the soil specimen, trim it to a regular shape, avoiding re-entrant corners, and weigh it.
  2. Wax Coating: Melt paraffin wax on a heater and apply two coats to the specimen. Measure the mass of the waxed specimen (Mt).
  3. Water Displacement: Fill the water displacement apparatus and close the valve upon overflow. Place a measuring jar below the overflow tube, open the valve, and slowly immerse the waxed specimen. Collect the overflowed water to determine its volume (Vt).
  4. Post-Test Steps: Remove the waxed specimen, dry it, peel off the wax, and cut it into two pieces for water content determination.

Calculations

Use the following calculations for each determination:

SI. No. Observations and Calculations Determination No.
1 Mass of specimen (M)
2 Mass of waxed specimen (Mt)
3 Volume of waxed specimen by weight displacement (Vt)

Calculations

  1. Mass of wax = Mt – M
  2. Volume of wax (Vp) = (Mt – M)/ Pp
  3. Volume of specimen (V) = Vt – Vp
  4. Water content
  5. Dry density = (M/V)/(1+w)

Results

The dry density of the soil is calculated using the formula: Dry density of soil = _______g/ml.

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