Corrugations - how are they formed

Colin, in addition to your information, there is a 3 part write up on corrugations at http://www.abc.net.au/science/k2/trek/default.htm

Colin
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?

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.

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 !!!
shane

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

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,

Kezza