ANS:B - Archimedes' principle

The principle involved in the relationship between the submerged unit weight and saturated weight of soil is Archimedes' principle. According to this principle, the buoyant force exerted on a body submerged in a fluid is equal to the weight of the fluid displaced by the body.

This principle can be applied to calculate the saturated weight of soil, which is the weight of soil particles plus the weight of water occupying the void spaces between the particles. The submerged unit weight of soil is the weight of soil particles per unit volume when the soil is fully saturated and submerged under water. The relationship between the two is given by the equation:

Submerged unit weight = Saturated unit weight - The unit weight of water.

Where the unit weight of water is assumed to be 1 kN/m3.