Where do Potholes come from?
Potholes are formed in the sub-base in places where it has little or no gravel cover. They frequently occur in level surfaces or where a downhill levels off and then turns up hill. They seldom occur on sloping drives, or on well-drained drives with a camber.
Next time you take a walk down a track do this. If it's a wet season, find a puddle (A pothole full of water). Now with the toe or heel of your welly kick at the edge of the puddle, very soon you will loosen the sub-base and start a hole of your own. Now try this again in the summer, you will find yourself kicking a concrete like material that will eventually tear the heel off your boot! What's happening? Well the water gets in the aggregate and loosens its structure. The secret to preventing potholes is to keep the track well drained.
I remember being taught at school, many years ago! About a bloke called "Macadam" is that right? Is this the man who constructed the first tarmac roads? I recall that he said the road surface should have a camber on it to enable drainage to the curb. The surface was formed from tar, to provide a waterproof surface.
How potholes Form
This is how I understand the pothole forming process. Take a track constructed from scalpings or hoggin, or some other self-binding material. Its been raining, and the surface is wet with the occasional puddle in small depressions. As the vehicle tyre passes over, it forces water into the structure of the road surface starting the damage to the road.
However you can prevent this damage starting quite simply by covering the road with gravel. Imagine a 35mm to 50mm layer of gravel over the road. The surface of the track below the gravel is still wet, but the tyre does not come directly in contact with it. The tyre passes over, 30mm or 40mm away. The layer of gravel is actually protecting the structure of the road!
Tony ... "pothole expert" Hine ..... lol
Jan 2010 ...1389 views
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