Soil mechanics definition check: In geotechnical engineering, the ratio of the volume of voids to the total volume of a given soil mass is known as ________.

Introduction / Context:
This question tests core soil mechanics terminology used in phase relationships. Correctly distinguishing between porosity, void ratio, specific gravity, and water content is essential when analyzing compaction, permeability, compressibility, and settlement.

Given Data / Assumptions:

• Soil mass is considered as a three-phase system: solids, water, and air.
• Definitions follow conventional geotechnical engineering usage.
• Volumes are bulk volumes at the state of interest.

Concept / Approach:
Porosity n is defined as the ratio of the volume of voids Vv to the total volume V. Void ratio e is defined as Vv / Vs (volume of voids to the volume of solids). Specific gravity G (or Gs) relates the density of soil solids to water; water content w relates the mass of water to the mass of solids. Only porosity uses total volume in its denominator.

Step-by-Step Solution:

Verification / Alternative check:
Since V > Vs for any soil with voids, only porosity uses total volume in the denominator. If total volume were not used, the term would not represent the fraction of void space within the entire mass, which is the intuitive meaning of porosity.

Why Other Options Are Wrong:

• Specific gravity: ratio of densities of solids and water, unrelated to volumes Vv and V.
• Void ratio: Vv / Vs, not Vv / V.
• Water content: mass-based measure Mw / Ms, not a volumetric ratio.

Common Pitfalls:
Confusing porosity (Vv/V) with void ratio (Vv/Vs); both are dimensionless but have different denominators and ranges.

Final Answer:
Porosity