During the compaction of granular fill, an operator notices that the roller is 'bouncing' or 'walking out'. What is the most likely cause for this phenomenon?

Question: During the compaction of granular fill, an operator notices that the roller is 'bouncing' or 'walking out'. What is the most likely cause for this phenomenon?

Answer options:

• The soil is too dry for effective compaction.
• The vibratory frequency is too low for the roller speed. ✅ The soil has reached its maximum density and is over-compacting.
• The lift thickness is too shallow for the roller's weight.

Correct answer: The soil has reached its maximum density and is over-compacting.

Explanation: When a roller 'bounces' or 'walks out', it usually indicates that the material has reached its maximum achievable density under the current compaction effort. Continuing to roll can damage the equipment or the subgrade by over-compaction, which is inefficient.