Methods of test for soils, Part 33: Determination of the density in place by the ring and water replacement method
1971 Edition

The density ring utilized in the test must have a diameter at least three to four times larger than the biggest particle size in the soil sample. Typically, ring diameters range from 0.5 m to 2.5 m in increments of 0.5 m. Constructed from mild steel sheets with thickness between 4 and 8 mm, smaller rings are fabricated as a single piece, whereas larger rings consist of segments assembled onsite. The interior is shaped as a right cylinder with a height ranging between 10 and 20 cm. Horizontal flanges, 10 to 25 cm wide depending on ring diameter, are installed for stability along with stiffening elements to prevent deformation during testing. Prior to use, any loose debris or sharp edges are removed, and the ring is firmly placed on a leveled surface to ensure minimal disturbance and precise density measurement.

To accurately measure the excavation cavity volume, excavated soil is first sieved to separate stones retained on the sieve. The weight and volume of these stones are determined either by direct water displacement using a graduated flask or siphon can or calculated from their weight divided by the product of specific gravity and water unit weight. The cavity is then filled with water isolated by the ring and a sheet, and the volume of water used is recorded. The effective cavity volume is computed by subtracting the stone volume from the total water volume filled. This approach ensures precise volume measurement by accounting for the space occupied by coarse particles.

To avoid water loss during testing, ensure the plastic film used is in complete contact with both the soil surface and the interior of the density ring while filling. Water should be filled precisely to the pointer mark, monitoring the level for several minutes to detect any leakage. Walking on or dragging the plastic sheet is prohibited to prevent tears or leaks. For larger cavities, a calibrated tank with a hose is recommended for rapid filling followed by a smaller tank for precise volume control. For smaller or hard-to-access holes, utilizing a small calibrated container or siphon hose allows controlled water delivery. In case of leakage detection, repeat measurements using an intact plastic film to guarantee accuracy.

Moisture content is determined in accordance with IS 2720 Part II by obtaining representative soil samples, excluding large non-absorbent stones if surface dry. The dry density is derived from the wet density and moisture content using the relation: dry density equals wet density divided by one plus moisture content fraction (w/100). For soils containing coarse stones, the dry density of the finer fraction is computed by subtracting the weight and volume of stones from the total weight and cavity volume respectively, then adjusting for moisture content. This adjustment ensures that the influence of moisture on soil density is accurately reflected for reliable compaction evaluation.

Yes, the method is applicable to soils with large coarse particles or stones provided certain conditions are met. Stones exceeding the specified size limit are removed if density measurement is required only for finer fractions. Large stones can be broken into smaller pieces if necessary to fit equipment capacity, with all fragments weighed accordingly. Stone volume is determined either by water displacement or by calculating from weight and specific gravity. Moisture content sampling excludes large non-absorbent stones if surface dry. These provisions enable accurate density measurement even in soils with substantial coarse material.