Potholes are a major problem in India. They¡¯re dangerous anywhere in the world, causing accidents that kill or maim, but especially here because we take so darned long to fix them. But there¡¯s more to how a pothole forms than just cars driving on roads.
It¡¯s a law of science that pretty much any material expands and contracts in heat and cold respectively. That¡¯s why water put into a pressure cooker attempts to force its way out when boiled into steam. That¡¯s also why your doors might tend to jam in the summer, especially if they don¡¯t have much clearance from the floor.
In the same way, asphalt laid for roads also expands when exposed to the baking sun and contracts in colder weather. It¡¯s obviously not noticeable, but you can see the signs. After a newly-finished road has been left to the elements for a while, this constant cycle of expansion and contraction creates small cracks in the asphalt.
These cracks don¡¯t do so much on their own, but they do create tiny gaps in the asphalt, while also weakening it. Rainwater can then permeate into these cracks, gradually eroding away the underlying dirt in the road¡¯s foundation, weakening it further. After that, it¡¯s just a matter of gravity, pulling the asphalt down into the hollows created, forming the beginnings of a pothole.
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Once this has happened, you can guess what happens when a car¡¯s wheel dips into this tiny rut. Each time, it flings away some of the dirt and asphalt, deepening and widening the hole over time. It¡¯s worse during the monsoons, because these holes fill with water. Now, when a car tyre drops into it, it¡¯s suddenly pressurizing all the water in there, and it needs to escape. Some of it is sloshed out around the wheel to make a splash, but the rest of it may be forced deeper into surrounding cracks in the asphalt at high pressure.?
It¡¯s no wonder then the best time to fix potholes is just before the monsoons. It¡¯s also obvious why holes needed to be tended to, if not for safety¡¯s sake. Left to itself, an entire road could over time just become one giant pothole, so it¡¯s not even a road anymore. Maintenance crews can¡¯t stop the effects of heat and cold on the road, but they can make sure any holes are repaired as soon as possible to avoid damage building up.