Alligator Cracking
Alligator Cracking – is a series of interconnection cracks caused by fatigue failure of asphalt concrete surface under repeated traffic loading. Cracking begins at the bottom on the asphalt surface (base) where tensile stress and strain are highest under a wheel load. The cracks propagate to the surface initially as a series of parallel longitudinal cracks. After repeated traffic loading, the cracks connect, forming many-sided, sharp-angled pieces that develop a pattern resembling chicken wire or the skin of an alligator. The pieces are less than 2 ft. (.6m) on the longest side Alligator cracking occurs only in areas subjected to repeated traffic loading, such as wheel paths. Alligator cracking is considered a major structural distress and is often accompanied by rutting. This type of distress often will have two or three levels of severity often within one distressed area. If these portions can be easily distinguished from each other, they should be measured and recorded separately.
Low Severity Alligator Low: Fine, longitudinal hairline cracks running parallel to each other with one or only a few interconnecting cracks. The cracks are not spalled. This clack is in a wheel path and is oriented in the direction of travel
Medium Severity Alligator Medium: Further development of light alligator cracking into a pattern or network of cracks that may be lightly spalled.
High Severity Alligator High: Network or pattern cracking has progressed so that the pieces are well defined and spalled at the edges. Some pieces may rock under traffic. Potholes of all sizes are recorded as high severity alligator cracking.