Soil mechanics — properties of gravels as an aggregate fraction Which consolidated statement about gravels is most appropriate in introductory soil/aggregate classification?

Introduction / Context:
In soil classification and aggregate grading, “gravel” denotes the coarser, cohesionless fraction above sands. Understanding its basic mechanical and volume-change behavior guides foundation and pavement design decisions, particularly regarding compaction, drainage, and susceptibility to heave/shrinkage.

Given Data / Assumptions:

• General engineering classification (e.g., gravels vs. sands vs. fines).
• Typical, not code-specific, size descriptions.
• Clean gravels without excessive fines.

Concept / Approach:

Gravels are cohesionless; their strength derives from interparticle friction and dilation under load. Particle sizes begin above the sand fraction (about 2 mm) and extend upward through coarse gravels and cobbles depending on the system used (some standards define 2–60 mm or 4.75–75 mm bands). Unlike clays and silts, clean gravels show negligible swell on wetting and minimal shrinkage on drying because they lack the active clay minerals responsible for volumetric changes.

Step-by-Step Solution:

Verification / Alternative check:

Unified/Indian/road specifications use slightly different size cutoffs, but all place gravel above sand sizes and treat gravels as coarse, cohesionless aggregates with minimal volume-change tendencies.

Why Other Options Are Wrong:

• Picking any single statement misses the full description; the comprehensive choice “All of the above” is most accurate.

Common Pitfalls:

• Assuming behavior of gravelly soils with high fines content; fines can introduce cohesion and volume change.

Final Answer:

All of the above.