![SHREE MALLIKARJUN COLLEGE CLASS: FYBSC-SEC
SAFETY: Handle the hot apparatus carefully
-Dr. Mithil S. Fal Desai
Aim: Determination of bulk density of soil sample.
Apparatus/Instrument: Beaker, measuring cylinder, desiccator, and electric oven.
Theory: The density of soil is an important parameter to understand the quality of soil. Soil bulk
density helps to understand the soil porosity, root depth, soil biological activity, root proliferation,
and nutrient availability. The bulk density is a measure of soil compaction. It is calculated by
measuring the dry weight of soil divided by its volume (Cylinder Method). This volume comprises
the volume of soil particles and the volume of pores among soil particles.
Bulk Density =
𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑑𝑟𝑦 𝑠𝑜𝑖𝑙
𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑐𝑐𝑢𝑝𝑖𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑑𝑟𝑦 𝑠𝑜𝑖𝑙
Soil density can be also measured by the water displacement method (Archimedes Method) where
a soil sample is coated in wax and then placed in water to measure the volume by determining the
quantity of water displaced. However, this method is not useful if the soil sample is susceptible to
surface wax intrusion.
Bulk density can be expressed in terms of g/mL or g/cm3
.
Procedure:
1) Heat about 50-100 g of the soil at 110 ◦C in an oven for 1 h to remove the adsorbed moisture.
(Prolong heating may be required to remove moisture)
2) Clean and dry a 50 mL measuring cylinder and measure its empty weight.
3) Pour the air-cooled dry soil into the measuring cylinder.
4) Gently tap and vibrate the measuring cylinder to avoid the air pockets.
5) Note down the weight of the measuring cylinder with soil and the volume of the measuring
cylinder occupied by the soil.
Note: Do not compact the soil by any external mechanical means.
Results: i) Bulk density of the soil= _____g/cm3
.
Further reading
1) IS 2720-28 (1974): Methods of test for soils, Part 28: Determination of dry density of soils
[CED 43: Soil and Foundation Engineering]
Questions.
1) Why one needs to dry soil to measure soil bulk density?
2) Explain Archimedes' principle.
3) Write the detailed procedure to measure soil density by Archimedes' principle.
4) Can we determine the moisture content by heating the soil sample at 250 ◦C?](https://image.slidesharecdn.com/determinationofbulkdensityofsoilsample-230727031231-d008319a/85/determination-of-bulk-density-of-soil-samplepdf-1-320.jpg)
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Measure Soil Bulk Density
- 1. SHREE MALLIKARJUN COLLEGE CLASS: FYBSC-SEC SAFETY: Handle the hot apparatus carefully -Dr. Mithil S. Fal Desai Aim: Determination of bulk density of soil sample. Apparatus/Instrument: Beaker, measuring cylinder, desiccator, and electric oven. Theory: The density of soil is an important parameter to understand the quality of soil. Soil bulk density helps to understand the soil porosity, root depth, soil biological activity, root proliferation, and nutrient availability. The bulk density is a measure of soil compaction. It is calculated by measuring the dry weight of soil divided by its volume (Cylinder Method). This volume comprises the volume of soil particles and the volume of pores among soil particles. Bulk Density = 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑑𝑟𝑦 𝑠𝑜𝑖𝑙 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑐𝑐𝑢𝑝𝑖𝑒𝑑 𝑏𝑦 𝑡ℎ𝑒 𝑑𝑟𝑦 𝑠𝑜𝑖𝑙 Soil density can be also measured by the water displacement method (Archimedes Method) where a soil sample is coated in wax and then placed in water to measure the volume by determining the quantity of water displaced. However, this method is not useful if the soil sample is susceptible to surface wax intrusion. Bulk density can be expressed in terms of g/mL or g/cm3 . Procedure: 1) Heat about 50-100 g of the soil at 110 ◦C in an oven for 1 h to remove the adsorbed moisture. (Prolong heating may be required to remove moisture) 2) Clean and dry a 50 mL measuring cylinder and measure its empty weight. 3) Pour the air-cooled dry soil into the measuring cylinder. 4) Gently tap and vibrate the measuring cylinder to avoid the air pockets. 5) Note down the weight of the measuring cylinder with soil and the volume of the measuring cylinder occupied by the soil. Note: Do not compact the soil by any external mechanical means. Results: i) Bulk density of the soil= _____g/cm3 . Further reading 1) IS 2720-28 (1974): Methods of test for soils, Part 28: Determination of dry density of soils [CED 43: Soil and Foundation Engineering] Questions. 1) Why one needs to dry soil to measure soil bulk density? 2) Explain Archimedes' principle. 3) Write the detailed procedure to measure soil density by Archimedes' principle. 4) Can we determine the moisture content by heating the soil sample at 250 ◦C?