Key factors influencing soil compaction: Which of the following parameters significantly affect the achievable dry density and resulting soil structure during field or laboratory compaction?

Introduction / Context:
Compaction improves strength and reduces compressibility and permeability by reducing void ratio. The dry density attained depends on several controllable and inherent factors. Understanding these allows engineers to select appropriate specifications (energy, moisture window) and equipment for different soils.

Given Data / Assumptions:

• Standard or Modified Proctor frameworks apply.
• Different soils respond differently to compaction methods.
• Moisture adjustment controls fabric (flocculated vs. dispersed) in fines.

Concept / Approach:

Higher compactive effort generally increases maximum dry density and shifts optimum moisture. Method matters: vibration favors granular soils; kneading/impact helps plastic fines. Soil type controls the achievable density and the shape of the compaction curve. Moisture content relative to optimum strongly influences stiffness, swelling potential, and permeability post-compaction.

Step-by-Step Solution:

Verification / Alternative check:

Laboratory compaction tests show clear shifts in maximum dry density/OMC with energy and method; field rolling patterns corroborate these effects across soil classes.

Why Other Options Are Wrong:

Each parameter has a documented impact; selecting any single factor alone ignores the multi-variable nature of compaction.

Common Pitfalls:

Applying vibratory rollers on highly plastic clays; compacting far dry of optimum and risking post-wetting collapse; ignoring gradation control in granular fills.

Final Answer:

All the above