Meaning of Passes
Meaning of Passes
(OP)
Simple question - will be interesting to see how this plays out engineer-wise and country-wise:
If the specification says that X passes of a compactor are required, does that mean that X is a single pass over a spot or a back and forth (double) pass?
If the specification says that X passes of a compactor are required, does that mean that X is a single pass over a spot or a back and forth (double) pass?





RE: Meaning of Passes
RE: Meaning of Passes
RE: Meaning of Passes
RE: Meaning of Passes
RE: Meaning of Passes
Ryan Coggins, P.E., S.I.
http://www.linkedin.com/in/ryancoggins
RE: Meaning of Passes
One pass = one pass. Back & forth = 2 passes. New England.
Always assume to the conservative view without solid documentation to the contrary.
Ralph
Structures Consulting
Northeast USA
RE: Meaning of Passes
Let me be the first to add, I hate specs like this (hopefully it's not your spec, BigH).
f-d
¡papá gordo ain't no madre flaca!
RE: Meaning of Passes
RE: Meaning of Passes
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Meaning of Passes
Be nice Mike.
Given the number of ancient specs I've seen, as well as the some of unintended consequences of modifications to the MasterSpecs, the question really isn't surprising.
Ralph
Structures Consulting
Northeast USA
RE: Meaning of Passes
. . . that is unless you're specifying construction of a test pad.
f-d
¡papá gordo ain't no madre flaca!
RE: Meaning of Passes
RE: Meaning of Passes
RE: Meaning of Passes
I don't think this is universally true. With relatively clean granular materials (generally speaking, RD material rather than Proctor), one can often get perfectly adequate compaction with a procedure spec, e.g., 12" lifts, each compacted by 4 passes of a single-drum 10-ton vibratory roller. We often do dam filters that way, and it's no problem to get 70% RD. It's a whole lot easier than sand cones or even nukes in a material with coarse gravel. Sometimes a test fill helps to nail down the required number of passes for whatever roller the contractor brings out. It might only be two.
This only applies to granular material, for which the exact moisture content is not too critical. For Proctor material, no way!
DRG
RE: Meaning of Passes
If you are using past contractors ability to achieve a requirement with their equipment, and using with another contractor and different equipment, I still say bad specifying.Are you specifying the same amplitude, frequency and speed for the roller too? Is the material exactly the same as far as angularity, etc.?
I have seen to many instances of poorly functioning equipment to know that one contractor's POS is not the same as the next guys, nor does one operator run the equipment at the same settings as the next.
At a minimum, I would want to run a test section, with reasonable amounts of testing to show that the contractor is achieving what you want. What you want is not to run the hours up on the equipment, but to achieve the desired degree of compaction, right?
RE: Meaning of Passes
Four passes of the 10-ton vib roller on a 12" lift is probably going to be overkill in any clean material. For large volumes, the contractor may want the test fill in order to be allowed to cut back on the passes. We have a standard 10-ton compactor spec that gives beats per minute, centrifugal force, and such, but it really isn't very difficult to hit 70% with any decent-sized equipment on clean fill. I don't think there is a whole lot that can go wrong with using a vib roller if the eccentrics are spinning at the correct speed (and the original factory eccentrics are still there).
You may be able to get 70 with 4 passes of a D8 on a 12" lift.
On a side note, we try not to overcompact filters because particles break down and create layers of low permeability at the top of each lift. [Note - I have no experience with fills where the minimum was more than 70.]
RE: Meaning of Passes
Go Dirt.
RE: Meaning of Passes
All I was pointing out is that while you state one thing, you are looking for another, and you may not always get that by prescribing the method. As you stated, "if the eccentrics are spinning at the correct speed (and the original factory eccentrics are still there).) This was the same thing I was pointing out. Add to that some operator that does not like the way the vibration feels on his manhood, and who knows what you get.
RE: Meaning of Passes
On a recent project with a small amount of dam embankment being replaced, they brought out a Wacker radio-controlled two-drum vib pad-foot roller that I'd never seen before. I didn't think it would work very well for the clayey core material, but with lots of passes, it got 98% of std. according to sand cones (lifts 8" LOOSE). They ran the vibrator, but I'm not sure if that really helped much. It was small enough that they could move it into small spaces by crane.