Corrugations - how are they formed

Submitted: Wednesday, May 29, 2002 at 00:00
ThreadID: 1227 Views:7618 Replies:6 FollowUps:4
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My recent posting on "Trailers in the desert" created a deal of interest. I noted there seemed to be a difference of opinion on how corrugations are caused, so I did a 'Google' search on the Web to try and satisfy my curiostity. This is a precis of what I found. --- Traffic causes corrugations in two ways: 1. The force of the tires and the road surface. 2. The motion of vehicles bouncing up and down on their springs and tires. Other causes - Increasing tire hardness, vehicle acceleration, deceleration, turning, and speed also increases the degree of damage. 2WD causes more corrugations then 4WD. All wheels have a similar effect whether driven or not driven. Size of corrugations was in proportion to tyre diameter. The solution to reducing corrugations - reduce speed and tyre pressure. Comment - no rocket science involved here, mostly common sense.
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Reply By: Member - Sam - Thursday, May 30, 2002 at 00:00

Thursday, May 30, 2002 at 00:00
Colin, in addition to your information, there is a 3 part write up on corrugations at
AnswerID: 3914

Follow Up By: Colin - Thursday, May 30, 2002 at 00:00

Thursday, May 30, 2002 at 00:00
Thanks Sam - I looked at that one. I was surprised at how many 'hits' I got to "corrugations on gravel roads". The Google search engine is good - amazing how much info is available on any subject.
FollowupID: 1663

Follow Up By: Member - Sam - Thursday, May 30, 2002 at 00:00

Thursday, May 30, 2002 at 00:00
No probs Colin. Was wondering if you had read those articles. I read them a while ago, then went on to read the rest of the articles. Dr Karl is a great read and seems an avid outback traveller aswell. Cheers, Sam.
FollowupID: 1666

Reply By: Bob - Thursday, May 30, 2002 at 00:00

Thursday, May 30, 2002 at 00:00
I followed your lead and did the Google search. It seems Australia, Mongolia and Alaska are the corrugation capitals.
Clearly going slower, and with reduced tyre pressures must help. Gentler braking and acceleration will also reduce surface damage.
It still leaves the question of the lightest way to tread with a given load - put it all on four wheels, or spread it over six.
My gut feeling is that spreading the load has to reduce surface damage but that ignores the effect of the unladen mass of the trailer (? about 300 kg) .
Any thoughts anyone?
AnswerID: 3930

Follow Up By: Axel +karen - Friday, May 31, 2002 at 00:00

Friday, May 31, 2002 at 00:00
Bob,, its realy only common sense ,, that can also be backed up by science , drag a 1kg bag of lead through the sand, drag a 1kg bag of feathers through the sand, only one causes damage ,yet both are 1kg. tread lightly,spread the weight,. Axel.
FollowupID: 1673

Reply By: Tony- Friday, May 31, 2002 at 00:00

Friday, May 31, 2002 at 00:00
Interesting. On a trip through the desert regions a couple of years ago, I noticed that corrugations on the tracks were worst at points approaching and leaving 'obstacles', ie track intersections, creek bed crossings and places where people would pull off the track to enjoy the view etc. This lead me to believe that vehicles slowing down and accelerating away (changing velocity) from the 'obstacles' were causing the corrugations. Of course, once the corrugations had started, the problem is then perpetuated as one slows down for the corrugations and then accelerates when they ease! Sort of like a dog chasing its tail.
AnswerID: 3946

Follow Up By: Colin - Monday, Jun 03, 2002 at 00:00

Monday, Jun 03, 2002 at 00:00
Yes, all that is in the reports I read - the worst corrugations on the lower part of the CSR are on the flat harder surfaces, where weight, tyre pressure and speed is probally the cause!
FollowupID: 1683

Reply By: shane - Sunday, Jun 02, 2002 at 00:00

Sunday, Jun 02, 2002 at 00:00
terrain also seems to have a big effect as well. ie: cape york on the bauxite gravel the corrugations seem higher. where there is truck or bus traffic the corrugations are further apart and are more prevalent on higher speed sections like straights.
Victoria's high country: on hard packed dirt the corrugations are lower but truck traffic spreads them apart and they are more prevalent on the approach and departure of corners.
One thing is common though...wherever you get them they are a pain in the butt !!!
AnswerID: 3965

Reply By: Guy - Wednesday, Jun 05, 2002 at 00:00

Wednesday, Jun 05, 2002 at 00:00
I read Karls-Webpages - karl go it partly right but he forgot like most answers that corragation does NOT exist on very HARD surfaces like STEEL or CONCRETE. Corragation form exactly like pot-holes form. Because the SUBSOIL 100mm to 600mm down is ELASTIC. it is like a spring. Concrete Freeways do NOT have corragation because their subbase upt to 3 feets down is compacted hard. What constitute a "corragation hump " is interesting. It is made up of large grains (up to 6mm in Diameters) and tiny particule which can fly in the air like dust. Only a few microns. Yes dust and specially bull dust can corragate to a maximum size. Corrragation is not formed by the weight but by the mass. There is confusion between weight and mass in the answers. Guy
AnswerID: 4012

Reply By: Kezza - Wednesday, Jun 12, 2002 at 00:00

Wednesday, Jun 12, 2002 at 00:00
Yes all of the above but the main cause you will find is a degree of axle tramp thats why you notice it most at slowdown or take off points on hills and corners( dont forget traffic flows in both directions so a slowing down point for one vehicle is an acceleration point for another) and as the axle tramp effect comes into play slight corrugations occur and then the impacting effect of the following vehicles causes larger and larger corrugations ,

want to test this theory? spend some time sitting on a sand track with lots of traffic and see what happens - limited slip diffs do minimise this effect.

As for plasticity in the ground - that theory is ok till you notice that corrugations still form on solid roadbases and sand soft surfaces like semi plastic mud dont corrugate usually and mostly potholes form because of plasticity and water in and on the track.

Just my observations and experience,

AnswerID: 4139

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