How do corrugations form?

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Originally Posted by chopper

I think pedestrians crossing the road cause the corrugations and the council maintain them. I was told by an old bloke that grading is pointless without a proper deep ripping first as the corrugations go a lot deeper than what you see and the usual quick skim with the blade over the top is next to useless.

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You are sort of correct,to get them out you need to cut them out.
Its pointless deep ripping unless you can cut all the material out to the bottom of the rip,re-lay it and re-compact it.NO shire has the maintence budget to do such expensive work.
Not removing all the material creats 2 new problems,tram lines which will remain until cut out just like a corrougation.Much more dangerous as they make a vehicle difficult to steer.The other problem,rainfall enters the road thru the rip marks and waterloggs the running surface.
Corrugations can be sucsessfully repaired in winter.The day before I grade a road in winter I cut all corrugations and potholes out to their depth from the crown to the shoulder,exsess material is left in a windrow on the shoulder,the multi tyre roller rolls my work.The next day I re-form the road to the correct crossfall,easy peasy;););););)
Andrew

The Spoof : Pothole funny stories

this is close to helping I think...

There was research done years ago here on forestry roads. They concluded that trucks running lower tyre pressure would stop forming corrugations and could even repair them.

So for a while logging trucks had active tyre pressure control in cab. But I think it has since been dropped for cost reasons.

the repairs they are making on the Silver City Highway to Tibooburra seem to be effective.

they truck in a special white coloured roadbase , what looks like crusher dust , local dirt/soil and I believe cement powder.

the road is cut back then the roadbase mix is turned over and over with a grader and water tanker to a certain moisture and is cut , rolled and tamped several more times.

the finished product is super smooth and quiet to drive on.....better than bitumen

they are interspersing this with bitumen strips all along the hwy ....I guess until it's completely bitumen.

Sandy pavement materials are more susceptable to corrugations. The lack of fine clay materials means that the material cannot bind together and segregates. You will notice that coarser materials will gather at the top of the humps. This material has been flicked there by wheel action. The fines materials are lost from the bottom of the corrugations as dust or washed away. When Landyandy rips the basecourse to say 200mm, all he is doing is remixing the material into a homogeneous material again, and sometimes adding water to bring up the moisture content and help bind the material again.

Again ramblingboy42, they are bringing in fines material to balance up the material grading, and cement (or possibly lime) used to bind the material and slow tendancy to break down again. There are several products around that are used to bind pavement materials, an simple old good one being molasses.

I fail to see how corrugations at depth can influence the surface. If the top 200-300mm of material is of a correct grading with sufficient fines (clay) to bind the surface, then corrugations will not develop. Weakness at depth will affect loading carrying ability, not surface defects such as corrugations.

Cheers,

Our grader driver has a unique solution, firstly in note we do not have a crusher, the accountant sold it:twisted:. Apply a layer of river stones ranging fron cricket ball to Sheridan size, then wait for the trucks to pound them in. Certainly no harmonics as you play dodgems. :mad:

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Originally Posted by ramblingboy42

the repairs they are making on the Silver City Highway to Tibooburra seem to be effective.

they truck in a special white coloured roadbase , what looks like crusher dust , local dirt/soil and I believe cement powder.

the road is cut back then the roadbase mix is turned over and over with a grader and water tanker to a certain moisture and is cut , rolled and tamped several more times.

the finished product is super smooth and quiet to drive on.....better than bitumen

they are interspersing this with bitumen strips all along the hwy ....I guess until it's completely bitumen.

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You are talking cement stabilisation here,yes it does work,but only into the short term.In our experience around 3 years and it starts to fail,EXPENSIVE!!!!
We are looking into using geofabric and a geo mesh to repair failures,already have done our first trial,EXPENSIVE.With the increased number of heavy vehicles using roads that were never designed to carry their axel weights the roads are faling to bits.
Andrew

Couple of bits of personal experience:

Local flat dirt road, like a highway, 60 to 100 kph, has corrugations in summer but absolutely none in winter, which supports the dust theory.

The Glenelg River Rd in the Grampians from the Mt Victory Rd down to the Vic Valley has bad corrugations on all the tight corners all year round where people brake / accelerate. It's gravel up the top with more clay as you get lower down.

Maybe two different causes.

DL

To answer your original question:

[Corrugations] "...are formed by the action (and harmonics) of the suspension and tyres of the track's major-user vehicles on the soil."
Tom Sheppard Four-by-four driving/Vehicle-dependent Expedition guide/The Land Rover Experience

That's the most precise explanation, from a chap who definitely knows a thing or two about off road driving.
Cheers

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Originally Posted by AndyG

Our grader driver has a unique solution, firstly in note we do not have a crusher, the accountant sold it:twisted:. Apply a layer of river stones ranging fron cricket ball to Sheridan size, then wait for the trucks to pound them in. Certainly no harmonics as you play dodgems. :mad:

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I can hire you one Andy ................. :D

https://www.aulro.com/afvb/images/im...014/05/896.jpg

Got three of these. ;)