The densities of a soil sample is prepare in correct decreasing order.

Question

Examoogle · Accepted Answer

The correct answer is Option C: Saturated, bulk, dry, submerged. The order of densities for a soil sample, from highest to lowest, is Saturated density ($\gamma_{sat}$), Bulk density ($\gamma_{bulk}$), Dry density ($\gamma_d$), and Submerged density ($\gamma'_{sub}$). This ordering depends on the water content and the buoyancy effect acting on the soil particles.

Step-by-Step Solution & Concepts:
The order of densities for a soil sample, from highest to lowest, is Saturated density ($\gamma_{sat}$), Bulk density ($\gamma_{bulk}$), Dry density ($\gamma_d$), and Submerged density ($\gamma'_{sub}$). This ordering depends on the water content and the buoyancy effect acting on the soil particles.

Working Principle: Saturated density is maximum because all voids are filled with water and water adds weight without increasing volume. Bulk density is lower than saturated because the degree of saturation is less than 100%. Dry density is lower than bulk as the weight of water is removed. Submerged density is the lowest because it is defined as the saturated unit weight minus the unit weight of water ($\gamma_{sat} - \gamma_w$), accounting for the upward buoyant force in underwater conditions.

Key Formulas: $\gamma_{sat} = \frac{(G+e)\gamma_w}{1+e}$ — Saturated Unit Weight; $\gamma_d = \frac{G\gamma_w}{1+e}$ — Dry Unit Weight; $\gamma' = \gamma_{sat} - \gamma_w$ — Submerged (Effective) Unit Weight

Key Points: For most soils, $G \approx 2.65$ and $e$ varies, but the inequality $\gamma_{sat} > \gamma_{bulk} > \gamma_d > \gamma'$ holds universally.; Submerged unit weight is effectively about 50% of the saturated unit weight.; Dry density is used as a measure of soil compaction, while submerged density is used for calculating effective stress in submerged soil strata.

Advantages: Provides a clear hierarchy for soil phase relationships.; Critical for calculating overburden and effective stress in geotechnical engineering.

Disadvantages: Assumes a constant void ratio for comparison, which may vary under different load conditions.

Applications: Earth dam stability analysis.; Foundation settlement calculations in submerged soils.

Additional Info: Option A is incorrect because it suggests bulk is denser than submerged but fails the logical order against dry.. Option B is incorrect as bulk density is consistently higher than submerged density for any non-saturated soil.. Option D is incorrect as it places bulk density above saturated density, which is physically impossible as saturated density represents the maximum possible bulk density at a given void ratio.

Answer: C is correct — Saturated density is the highest density state of soil followed by bulk density, dry density, and finally submerged density due to buoyancy.

Exam Tip: Remember that $\gamma_{sat} > \gamma_{bulk} > \gamma_d$ and always keep in mind that $\gamma' = \gamma_{sat} - \gamma_w$ which effectively makes it the smallest value.

Examoogle · Answer

Option A: Saturated, submerged, bulk, dry

Examoogle · Answer

Option B: Saturated, bulk, submerged, dry

Examoogle · Answer

Option D: bulk, saturated, submerged, dry

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