A geotechnical report indicates that the optimum moisture content (OMC) for a granular fill material is 12%, and the maximum dry density (MDD) is 1950 kg/m³. During compaction, field testing shows the current moisture content is 8%. What action should the operator take to achieve the specified compaction?

Question: A geotechnical report indicates that the optimum moisture content (OMC) for a granular fill material is 12%, and the maximum dry density (MDD) is 1950 kg/m³. During compaction, field testing shows the current moisture content is 8%. What action should the operator take to achieve the specified compaction?

Answer options:

• Increase vibratory amplitude and speed. ✅ Add water to the material and re-compact.
• Decrease vibratory amplitude and speed.
• Proceed with compaction, as dry conditions improve density.

Correct answer: Add water to the material and re-compact.

Explanation: If the moisture content is below the Optimum Moisture Content (OMC), adding water is necessary for the soil particles to lubricate and achieve maximum dry density effectively. Compacting dry material significantly below OMC will not achieve the required density.