See for yourself. Drive a tractor,car or other vehicle over loose ground and let it stop. Watch for movement down. It's probably at a decreasing rate with time, probably in seconds or less. Then time how long it takes a roller to pass a given place at top speed. Probably in less than a secnd for n "effective" pass. Change speed and observe. Somewhere in that experiment with observations and timing, a happy speed will be decided on. Soil types probably will change the outcomes.
I think I'll just lay out 2 pass widths and shoot em. Make a slow pass and a fast pass and shoot em again. Shouldn't be more than a couple hundredths difference between them if I'm right about the load.
Yes, it makes a difference in the compaction efficiency. The goal is to impart the compaction energy normal to the surface. As the speed increases, the compaction drum tends to create more of a surface wave and pushes the soil at angle. This reduces the effective compaction energy going vertically into the soil and increases the potential for pumping in soils with high moisture content. How much? Depends on the size of the compaction equipment relative to the soil type.
Check DynaPac, Caterpillar and Bomag.....all have efficiency curves for their equipment and will show the forward speed relationship.
if you are writing a method spec, than by all means, you need a test strip so you can determine weight, speed, and all other parameters of the compaction method. If not, than contractor must meet the performance criteria and who cares how he does it as long as it passes the CQA checks. I would not recommend the method spec approach...
I agree that it does matter even with a static roller for the reasons already mentioned.
Check your local DOT spec book and it will likely have a maximum rate of speed for the paver, the vibratory roller and the static roller. Obviously paver speed is for the full width of the pass. Review the roller train for maximum speed and width of each roller. I'll bet it takes 2 to 3 vibratory passes to get compaction. So a 6' drum roller on a 12' lane advances at BEST 1/4 the speed of the paver. This is why you'll typically see two vibratory rollers on production paving. While the static roller can help top off the density, I've not seen any contractor in the last 25 years use one for anything but taking out the roller marks.
CVG: I would tend to agree with you on staying away from means and methodology, but break out the vibratory roller spec's and see where high speed rolling "over-runs" the vibrators and creates ripples in the mat. We had a local contractor pull this stunt and ruin the ride quality of a new overlay about 15 years ago. They're no longer in the paving business. I think they actually met the density spec, but obviously violated the DOT speed limitations.
