Definitions for "ravelling"
The gradual failure of the rock mass by rock blocks falling/sliding from the opening perimeter under the action of gravity, blast vibrations or deterioration of rock strength. A gradual failure process that may go unnoticed. The term unravelling is also used to mean the same thing.
In asphalt paving, the progressive separation of aggregate particles from the surface downward or from the edges inward; ravelling is caused by lack of compaction, construction of a thin lift during cold weather, dirty or disintegrating aggregate, too little asphalt in the mix, or overheating of the asphalt mix.
The loosening of stones from the surface of a pavement.