Ways to increase the density (unit weight) of a soil mass: Which of the following mechanisms can increase the bulk density of a soil in the field or laboratory?

Introduction / Context:
Improving soil density enhances strength and reduces compressibility. Field operations (compaction) and natural processes (consolidation) change the phase composition and volume, altering bulk unit weight γ. Recognizing all mechanisms helps select appropriate ground-improvement techniques.

Given Data / Assumptions:

• Bulk density refers to mass per total volume of soil, including solids, water, and air.
• Changes may occur via volume reduction or mass increase (water infiltration), but engineering densification generally targets volume reduction.

Concept / Approach:
(A) Compaction expels air primarily, reducing void ratio e quickly, especially in granular soils. (B) Mineral grains are relatively incompressible, yet under very high stresses a small elastic compression exists, adding marginally to density. (C) Consolidation in saturated fine-grained soils expels water over time as excess pore pressure dissipates, reducing volume and increasing density.

Step-by-Step Solution:

Verification / Alternative check:
Proctor tests show density rise by air removal; oedometer tests show density increase via water expulsion; high-pressure tests reveal slight grain compression.

Why Other Options Are Wrong:

• “None of the above” contradicts well-known soil mechanics processes.

Common Pitfalls:
Assuming grains are perfectly incompressible; overlooking that expelling water requires drainage paths and time.

Final Answer:
All of the above