What is the submerged (buoyant) unit weight of soil?

• A. Effective unit weight
• B. Dry unit weight
• C. Saturated unit weight
• D. Moist unit weight

Answer: (A)

The submerged (or buoyant) unit weight of soil refers to the weight of the soil when it is submerged in water, which is determined by the difference between the saturated unit weight of the soil and the unit weight of the water. It is expressed mathematically as the saturated unit weight of the soil minus the unit weight of the water.

Effective unit weight is relevant in this context because it reflects the stress acting on soil components due to the buoyancy effects of water. When soil is submerged, the water provides an upward force, which reduces the effective stress experienced by the soil. This makes the effective unit weight essential for calculating loads and pressures in geotechnical engineering, as it directly impacts the soil’s properties and behavior under submerged conditions.

Other choices like dry unit weight, saturated unit weight, and moist unit weight represent different conditions of soil moisture and weight but do not correctly define the concept of submerged unit weight. They do not account for the buoyant effects that occur when the soil is submerged in water.