Question

A soil clod weighing 885 grams was coated with paraffin. The weight of the clod and the paraffin was 993 grams. The total volume of the clod when immersed in water was 492 cm³. If the mass water content of the clod was 18%, its particle density is 2.65 g/cm³ and paraffin's density is 0.89 g/cm³, determine (i) the bulk density, (ii) void ratio, and (iii) the degree of saturation. 2​

Answer 1

(i) To determine the bulk density of the soil, we need to know the volume of the soil without any voids. The volume of the soil including voids is 492 cm³, so we need to determine the volume of the soil particles in the clod.

First, we can determine the mass of the dry soil particles by subtracting the mass of the water from the total mass of the clod and paraffin:

Mass of dry soil particles = Total mass - Mass of water
Mass of dry soil particles = 993 g - (0.18 x 885 g)
Mass of dry soil particles = 850.3 g

Next, we can determine the volume of the dry soil particles by dividing their mass by their particle density:

Volume of dry soil particles = Mass of dry soil particles / Particle density
Volume of dry soil particles = 850.3 g / 2.65 g/cm³
Volume of dry soil particles = 321.4 cm³

Now we can calculate the bulk density of the soil:

Bulk density = Mass of dry soil particles / Total volume
Bulk density = 850.3 g / 492 cm³
Bulk density = 1.728 g/cm³

(ii) The void ratio is the ratio of the volume of voids to the volume of soil particles. We can determine the volume of voids by subtracting the volume of dry soil particles from the total volume of the clod:

Volume of voids = Total volume - Volume of dry soil particles
Volume of voids = 492 cm³ - 321.4 cm³
Volume of voids = 170.6 cm³

Now we can calculate the void ratio:

Void ratio = Volume of voids / Volume of dry soil particles
Void ratio = 170.6 cm³ / 321.4 cm³
Void ratio = 0.531 or 53.1%

(iii) The degree of saturation is the ratio of the volume of water to the volume of voids. We can determine the volume of water by multiplying the mass of water by the inverse of its density:

Volume of water = Mass of water / Density of water
Volume of water = 0.18 x 885 g / 1 g/cm³
Volume of water = 158.7 cm³

Now we can calculate the degree of saturation:

Degree of saturation = Volume of water / Volume of voids
Degree of saturation = 158.7 cm³ / 170.6 cm³
Degree of saturation = 0.93 or 93%