Proctor in earth dam
Proctor in earth dam
(OP)
Hi!
We have a earth dam and we need to know some values of Modified Proctor because it doen´t exist any data before. Is useful to extract samples from the current earth dam for determining it?
I think that it could be useless cause that material is already compacted.
Thank you.
We have a earth dam and we need to know some values of Modified Proctor because it doen´t exist any data before. Is useful to extract samples from the current earth dam for determining it?
I think that it could be useless cause that material is already compacted.
Thank you.





RE: Proctor in earth dam
Assuming that you are trying to verify that the material was placed and compacted to some specified criteria, then the steps would be as follows:
1. Drill borings taking undisturbed samples.
2. Drill more borings to collect disturbed samples of each material type. Collect enough sample of each material to allow a laboratory Proctor test to be completed.
3. Determine the dry density of the undisturbed samples and compare to the Proctor values.
I ask again, why do you want the data? This a very expensive program for a dam of any real size and could require many borings.
Mike Lambert
www.shannonwilson.com
RE: Proctor in earth dam
The only way to determine the Proctor value is to test a sample of material taken from the site. Proctor values can be variable, depending on the soil, so using historical values from another location would be of no value.
RE: Proctor in earth dam
Geopavetraffic, firstly, we need some data about compaction characteristics because there are no data; secondly, the earth dam is very small, so the program wouldn´t be very expensive (5 borings). I had thought to follow a similar steps like yours.
Ron, I know it is possible to do Proctor after compaction, but I don´t know if the values in the method are representative, as the soil has already been compacted (with the Proctor method we are recompacted the sample again, I think).
RE: Proctor in earth dam
RE: Proctor in earth dam
So, be sure that it's really the Modified that you want to compare the sample densities with.
RE: Proctor in earth dam
Not sure I agree with this statement, particularly the "more pervious" part. The void ratio will be reduced with greater compaction, thus the permeability will be decreased.
I also wouldn't consider compacted, granular soils to be "brittle" unless cementation occurs.
RE: Proctor in earth dam
Here's where the more pervious part comes from:
If you compact a fine-grained soil to a given density much dry of optimum, you get get a little different structure, and the individual clods that make up the loose fill prior to compaction don't get smooshed (technical terminology) together quite as well by the sheep's feet. Hence, density within the lift is less uniform, and there is higher permeability (primarily in the horizontal direction). Even if you get a higher density (averaged within the lift) with a lower water content, the soil structure can still be the dominant factor. UNLESS, the dam is high, in which case wetting and the overburden pressure in the lower part of the fill could destroy all of the structure and it won't matter.
Ordinarily, the higher permeability is not a make-or-break for a dam, because it is not all that much higher.
The brittleness is a function of water content and density. If you put in a sample at some specific density (say, 90% of Mod, or 95% of Std, which are comparable), the drier it is, the stiffer and more brittle and prone to cracking it is until it gets saturated (which might not occur until the water is already flowing through transverse settlement cracks). The brittleness is observable in the lab or with a mattock on the fill. Hence, 90% of Mod at Mod OMC would be more brittle than 95% of Std at Std OMC. Also, wetter fill is easier to compact against irregularities in the foundation, structures within the dam, etc.
I have assumed that the OP is referring here to core material, not granular material, because he is talking about sampling to measure density and using the Proctor test. If he is using Proctor for granular material, he may have the wrong test, and he wouldn't be able to get samples that hold together enough for density tests. Proctor is generally limited to stuff with >15% fines, although with very fine sand (Florida sugar sand, for example), it can work OK with less.
DRG
RE: Proctor in earth dam
Again, have a problem with this statement:
The Proctor is commonly used in Piedmont and coastal plains soils alike...Standard for Piedmont, Modified for coastal plains. While we sometimes see a "double hump" Proctor curve in some of the fine sand materials, most of the time we get a clearly defined Proctor curve in materials that have 5% or fewer fines.
RE: Proctor in earth dam
You also need to be really careful if you plan to drill in a dam. You need to know what you're doing and so does the driller or you can create some major problems where none currently exist. You can hydraulically fracture materials, create preferential seepage pathways, etc, etc.
RE: Proctor in earth dam
D698 says "This test method will generally produce a well-defined
maximum dry unit weight for non-free draining soils. If this
test method is used for free-draining soils the maximum unit
weight may not be well defined, and can be less than obtained
using Test Methods D4253."
USBR 5500-86 (nearly identical procedure) says "This procedure is normally performed on soils that contain more than 15 percent fines. It may be used, under certain circumstances, for soils containing 5 to 15 percent fines."
RE: Proctor in earth dam
Recommend reading ASCE JGGE May 1999, vol 125, no.5 Field Performance of Compacted Clay Liners, Benson, Daniel & Boutwell.
They introduce the Line of Optimums, which is basically a line following the Zero Air Void,& connects, for instance, the Std & Mod Optimum points. The goal is to set a minimum compaction and keep the field results at or over the Line of Optimums, when the density results are plotted on the Proctor Diagram.
Depending on the size of equipment which is available, the material can be worked until the desired results are obtained. I have found this concept to be very helpful in the field.
RE: Proctor in earth dam
When were you in Central Florida and with which firm?
RE: Proctor in earth dam
RE: Proctor in earth dam
RE: Proctor in earth dam
You really have not answered why you want the data. You say you want compaction characteristics for the dam, but why? Compaction is an easy field test that with proper planning can be assumed to be related to important engineering properties such as strength, consolidation, and permeability just to name a few.
If you are trying to determine if the dam is will perform for its intended purpose, I suggest taking samples and running the appropriate laboratory tests to determine the engineering properties of interest.
Mike Lambert
www.shannonwilson.com