Aquaculture Engineering

Soil sampling - Three phase system of soil

Unit 3- Soil and its properties

Soil Sampling
Three phase system of soil

In general, the soil sample will be consisting of soil solids, water and air, which is designated as three phase system of soil. The sum of the air content and water content of a sample is called as voids. If the voids are completely filled with water such a sample is called as a purely saturated sample or 100% saturated sample. If the voids of soil is completely filled with air such a sample is called as purely dried sample, on the other hand if the part of the voids are filled with water and remaining with air it is called as a moist sample. The figure shows the diagrammatic representation of the three phase system of soil element in terms of volumes and weights respectively.

In figure,

V_a = Volume of air in the sample
V_w = Volume of water in the sample
V_s = volume of soil solids in the sample
V_v = Volume of voids in the sample
V = Total volume of the soil sample
W_a = Weight of air in the soil sample can be considered as zero.
W_w = Weight of water in the soil sample
W_s = Weight of soil solids in the sample
W = Total weight of soil sample.
Further V_v = V_a + V_w
V = V_s + V_v
W = W_w + W_s