Compaction
Compaction
(OP)
We have a drainage layer of 1-1/2" clean stone with no more than 2% passing the No.40 sieve. This is part of a drainage system.
How do you specify the compaction for this type of material?
With the lack of fines, is it possible to spec it using the Proctor dry density value?
Dik
How do you specify the compaction for this type of material?
With the lack of fines, is it possible to spec it using the Proctor dry density value?
Dik





RE: Compaction
In reality, clean rock compacts very easily if vibrated and confined.
RE: Compaction
RE: Compaction
RE: Compaction
even in a reasonbly densified state, aggregate of this size should still be freely draining. for all practical purposes, i don't usually suggest spec'ing an inplace density for this material. i spec it similar to rock fill..."densify in 8 inch lifts in the presence of our testing personnel until no further densification is visible" (ie. densify until the testing personnel see it stop moving under compaction equipment and probe that it's firm). probe it regularly to check that it's firm and observe that it's stable under the equipment. if you can penetrate the backfill with a probe rod, it's likely not sufficiently densified. if you can work your probe rod to the handle, try rodding up and down in say 6-8 inch strokes. keep doing this and the probe rod will eventually back itself out as the particles rearrange (ie. densify) leaving a rather substantial cone shaped depression which sort of gives a shocking visualization of how loose the material truly is. i maintain that loose 57 stone can settle say something on the order of 1/2-1" per foot height of backfill.
RE: Compaction
RE: Compaction
RE: Compaction
RE: Compaction
RE: Compaction
If you do need to undertake compaction, I would suggest you look at either the information which the compaction plant manufacturers produce (Bomag have an extensive library technical on all sorts of plant and suitable materials to compact) or have a look at Table 6/1, Table 6/2 and Table 6/4 from the UK's Specification for Highway Works. Find a material with a comparable grading in Table 6/2, then look up on Table6/1 the requirements for compaction and then go to Table 6/4 to find suitable plant, depth of layer and number of passes. The 'Method 'placement has been designed to provide 'adequate testing ?(less than 10% air voids for cohesive soils) at conservative moisture contents' [DMRB; HA 70, Section 4].
As your material is granular, relatively single-sized, I would seriously doubt that a lab compaction will provide a range of moistures to place the material at, but would provide a target density that could be achieved with the material. If you are going to apply compaction to the drainage material, make sure the aggregate is strong enough to prevent particle break down during placement (Los Angeles) and is resistant to weathering (Magnesium sulfate soundness or similar). Also the rock type will be important, no argillaceous rock, chalk or colliery spoil.
RE: Compaction
Consider a procedure spec, e.g., 6" loose lifts each compacted by three passes of an Acme Mark 1 walk-behind vibratory-plate compactor, or equivalent, if the placements are small and you don't need a lot of density; for large areas, something along the lines of 12-inch loose lifts with four passes of a 10-ton vibratory smooth-drum roller, with water applied by hose in sufficient quantity to minimize capillarity, if needed.
RE: Compaction
The 'pit' is approximately 20'x40'x3' deep and will be subject to light and infrequent traffic. I didn't think that any type of Proctor testing is correct and based on the information/confirmation here, I'm using double passes of a Bomag BW65H on 12" lifts. This is a tandem walk behind machine that generates a centrifugal force of about 5000 pounds (22 kN) per drum. Alternatively, I'll accept a double pass with a D3 Cat which should be equivalent.
The equivalent relative density I'm looking for is about 55% (Gradation is tightly controlled with variations of about +/- 3% for the seive sizes selected.
Dik
Dik
RE: Compaction
RE: Compaction
On the matter of drainage layer, compaction and its affect on permeability, I'd be more concered about the end conditions. If you are stiving to have drainage go vertically into the media, where will it go from there? Is there a perforated pipe system? Are you hopeful that the water will then continue downward to the water table? Is the goal for the water to leave horizontally at the edge? Somewhere in the conceptual design of the drainage system, you need to make sure that there is sufficient capacity to allow the drainage media to function.
Interesting discussion.
f-d
¡papá gordo ain't no madre flaca!
RE: Compaction
RE: Compaction
Dik
RE: Compaction