Pothole
A pothole (sometimes called a kettle and known in parts of the Western United States as a chuckhole) is a type of disruption in the surface of a roadway where a portion of the road material has broken away, leaving a hole.
Formation
Most potholes are formed as a result of fatigue of the road surface. As fatigue fractures develop, they typically create a pattern known as crocodile cracking. The chunks of pavement between the fatigue cracks gradually work loose, and may eventually be plucked or forced out of the surface by continued wheel loads; this represents the beginnings of a pothole.
The formation of potholes is exacerbated by temperatures below the freezing-point of water. This is because water expands when it turns into ice, which in turn causes additional forces to be exerted on an already-cracked area of pavement or road. Once a pothole forms, it continues to grows as broken chunks of pavement become detached from the surrounding surface. The rate of deterioration tends to accelerate when a pothole fills with water, and components of the road surface are scoured loose as passing vehicles disturb the pothole and its contents. In temperate climates, potholes tend to form most often during rainy spring months, when the subgrade has been weakened by the presence of excessive water and consequent sinkholes. Leaking sewer or water pipes may also have contributed to the washing away of the supporting bed of soil or rock on which the road has been laid, in addition to any direct damage to the below-ground structure of the road itself. However, potholes are common throughout the world, including in the tropics or other regions where frost typically does not occur.
Potholes can grow to several feet in width, though they usually only develop to depths of a few inches. If they become large enough, damage to tires and vehicle suspensions is liable to occur. Serious road accidents can occur as a direct result, especially on motorways, where vehicle speeds are greater. Potholes are frequently almost invisible to road users from a distance.[1]
Repair
Pothole patching is the process of repairing imperfections in an asphalt-based road. It is a year-round activity, and is typically performed by the city or county street maintenance crews responsible for keeping the roads and bridges of a given locality in good condition.
Pothole patching methods fall into two distinct categories — cold mix and hot mix. As the nomenclature suggests, cold mix is a suitable material for the winter months, and hot mix is used during the warmer seasons of spring and summer.
Both hot-mix and cold-mix repairs involve similar application methods. The most widely used is known simply as "throw-and-go": the patching mix is thrown into the pothole, on top of any debris or water that may be present, and is compacted with a shovel by manual labor. This method is widely utilized due to its simplicity and speed, but the failure rate of the resulting repairs is extremely high.
A step up in terms of quality is the "throw-and-roll" method. Here, the patching mix is also thrown into the pothole manually without regard to any water or debris that may be present. Next, a truck slowly drives over the repaired pothole so as to compact the mix. The goal is to leave the compacted patch with a crown that sits circa one eighth to a quarter of an inch above the surrounding surface. This process takes approximately two minutes more per pothole than the throw-and-go method; but though this type of repair is slightly more time-consuming, the compaction of the mix makes for a more durable patch.
Perhaps the most familiar pothole patching method is the semi-permanent repair. In this method, the pothole is completely emptied of any water or debris. Next, the pothole is made square or rectangular by the trimming back of its uneven edges with a pavement saw. The pothole is cleaned out again before the patching mix is applied. Finally, the area is compacted with a single drum roller or a vibrating plate compactor. This semi-permanent method produces the densest and longest-lasting type of patch. However, it is more time-consuming, and requires more labor and equipment to perform.
One variation of this method involves the use of a 40-kilowatt or larger propane torch (also known as a "roofing torch"). The torch is used to dry out and heat the pothole, and once the cleaned and squared pothole has been dried and warmed it is sprayed or painted with bonding compound, or "tack". The patching mix is then applied and compacted as above, and a final coat of the tack is sprayed on top of the patch, extending beyond its edges by several inches. This method is used by some councils in Britain. When properly executed, such a repair can last years more than a throw-and-go, which can fail after a mere matter of months.
According to the Federal Highway Administration, regardless of which method is used, patches applied in the winter months typically do not hold up as well as those applied during the warmer months. The goal for winter patching should be to repair the road as quickly as possible in order to increase the safety and comfort of road users. That said, the throw-and-go method can be satisfactory if high-quality repair materials are used. The goal in the warmer months is typically to perform repairs of the semi-permanent type. Utilizing this method when the conditions are ideal will result in patches with a lifespan that is no shorter than that of the road itself.
Reporting of potholes
Some municipalities have introduced official pothole-reporting programs that take advantage of recent advances in technology. For instance, as part of its Citizens Connect initiative, the City of Boston (Massachusetts) encourages its inhabitants to electronically submit reports (with or without photos) of potholes, graffiti, damaged road signs or non-working street lamps using either its website or a dedicated app. The associated smartphone-generated GPS metadata (if available) can be accurate enough to allow a repair crew to identify the exact location of the pothole without an additional verbal description being necessary.[2]
See also
References
- ↑ Eaton, Robert A.; Joubert, R.H. and Wright, E.A. (December 1989). Pothole primer—A public administrator's guide to understanding and managing the pothole problem. Special Report. 81-21. U.S. Army Corps of Engineers—Cold Regions Research & Engineering Laboratory. p. 34.
- ↑ http://www.cityofboston.gov/DoIT/apps/citizensconnect.asp
External links
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