Field compaction — best soil type for vibratory rollers Vibration-based compaction is most effective for which of the following soil conditions?

Introduction / Context:
Different compaction equipment suits different soil types because the mechanism of densification varies. Vibratory rollers induce particle rearrangement by reducing intergranular friction momentarily, which favors free-draining granular soils.

Given Data / Assumptions:

• Equipment: vibratory roller.
• Target: achieve high relative density efficiently.
• Soil choices include granular and cohesive categories.

Concept / Approach:
Granular soils (sands and gravels) compact primarily by particle rearrangement. Vibration is highly effective, especially for well-graded dry or slightly moist sands where pore pressures do not build up. Cohesive soils (silts/clays), particularly plastic or highly compressible silts, respond better to kneading/sheepsfoot rollers due to their low permeability and structure.

Step-by-Step Solution:
1) Identify mechanism: vibration reduces interparticle friction and mobilizes rearrangement.2) Match soil: well graded dry sand has broad size distribution and drains freely.3) Expect rapid density gains and high compaction energy transfer with vibratory rollers on sands.4) Therefore, select well graded dry sand as the best match.

Verification / Alternative check:
Compaction charts in field manuals rank vibratory rollers as most suitable for sands/gravels and least for clays/silts.

Why Other Options Are Wrong:
Moist silty sand may respond, but silt fraction dampens vibration; clays and high-compressibility silts require kneading and have drainage issues.

Common Pitfalls:
Over-wetting sands, which causes pumping; using vibratory rollers on saturated silts leading to instability.

Final Answer:
well graded dry sand