Where do Potholes come from?

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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.

Why?
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.

Tarmac
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.

Prevent potholes
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!

Cheers
Tony ... "pothole expert" Hine ..... lol

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Jan 2010 ...1389 views

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TØny Hine

tonyhine-94555

Are your figures on gravel depth correct?

Good Question Angus... Just to correct some misconceptions that may come out of this article, I have had a lot of dealings with potholes over the years, however these are generally in people's drives, not highways. This is not a major issue as the general principle of pothole formation still applies to roads just as it does to a domestic drive or farm type tracks and drive ways. When I referred to a layer of gravel it's for the decorative purpose it has taken up on a domestic drive or path. Having said "decorative purpose" I also believe it serves another purpose in preserving the actual structure of the underlying drive. As to the question of depth of gravel on a drive, then the rule of thumb method for calculating this is to have a depth of gravel of twice the particle size. Aggregates are generally produced in a range of sizes, the English measurements for these were traditionally 3/8", ¾" and 1¼". With the advent of metrication these sizes became 10mm, 20mm and 40mm. The most common size used on a drive is ¾" this doubles up to 1½", therefore it is sensible to allow a depth of gravel of 2 inches. Some people prefer the 3/8" gravel, (as I do myself), however it is not commonly used on drives. The smaller size does Have a minor problem, 3/8" gravel is more easily transferred into the house, which is a problem for some people. To calculate the depth for using a 3/8" gravel, then doubling this up, it becomes ¾" (depth) and it is sensible to allow a depth of 1 inch. If you prefer metric, then just apply the same rules with your metric measurements. Cheers Tony... MS Access Hints, Tips & Videos "The more connections I make, the further I can reach across the world finding inspiration in every person that I meet." Matt Pyke, Artist "Universal Everything."

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Angus Whitton

anguswhitton-88567

Where do Potholes come from?

Fife Business | Fife Events | Fife News | Fife Marketing | A good article Tony, but are your figures on gravel depth correct? 50mm of gravel is almost two inches,... All the best Angus Whitton Fife Business Promoters

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David"HolisticPlace" Tucker

david-george-tucker-80336

Where do Potholes come from?

FANTASTIC!.......... LOL....In all seriousness, I found that fascinating, as I have never thought about why they should occur....or how to prevent them and as you know Tony, from my earlier blog, I need to know!:) Many thanks and I may well ring you if I can persuade the brother-in-law to get it done! David. Have you heard of a pharmaceutical company that really wants you to be well & healthy....? Is there a complementary, alternative health way ahead?

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