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1967pradyot (Geotechnical) (OP)
13 Jun 03 5:51
Hi

Why for any compaction of soil, it is stated that 95% of Modified Proctor or Standard Proctor dry density is to be obtained ?
If we specify 85% or 90% and do obtain the required strength, whether it is OK?  I want to know what exactly the justification of specifying that specfic ( generally 95%)degree of compaction.
Helpful Member!  Rjeffery (Civil/Environmental)
13 Jun 03 8:55
The short answer is that compaction is a way of trying to produce a uniformly dense mass of earth.  it produces strength as a byproduct of the densification.  If the mass of earth us uniformly compact then any settlement will be uniform as well (we hope).  by compacting to a lower percentage the settelment will be greater.  conversly, by compacting to a higher percentage the settlement will be less.  95% is chosen, I suspect, as a matter of engineering economy.
Helpful Member!(3)  MRM (Geotechnical)
13 Jun 03 13:00
The "95%" spec (usually specified when speaking in terms of the modified Proctor test) is somewhat arbitrary.  It has been proven to work in most common situations where an engineered backfill is required and most contractors expect that particular relative compaction in the spec so there is less chance that a required relative compaction in a spec will be confused.

In addition, 95% of the maximum Modified Proctor value usually corresponds to a relative density between about 65% and 75% depending on soil gradation, particle shape, angularity, etc.  A soil with a relative density in this range is considered "dense" by most geotechnical engineers.  Typically, a dense soil has good engineering properties under most applications; beneath foundations or behind retaining walls, for example.
Helpful Member!  BigH (Geotechnical)
13 Jun 03 18:45
MRM - yes, 95% is typically done in that way - still, would 94% be okay??  When constructing, people get bent all out of shape if you don't reach the 95% value.  Here in India, MOST requires 95% of the MDD of Heavy Tamping (similar to the Hernia Test - oops, the Modified Proctor) for embankments.  Why?  I don't know.  I've used 95% standard with no problems elsewhere.  Some people just like things to be "heavier" - the bigger the better.  I believe too that the 95% was put out by someone years ago and 'ell, it's here to stay since engineers just crop specs from one site to another - for the most part.  There was a fine paper written in Ground Engineering on the "95% Fixation" - I have a scanned copy I would be happy to send out (if my serer will allow the size - but I can send page by page).  If anyone is interested - bohica@indiatimes.com  .

I once had an argument with a junior engineer in our company.  He insisted on specifying 100% Standard Proctor (light tamping, roughly).  The fill was to support some lightly loaded to moderately loaded foundations using good engineered fill.  I was leaning on him to accept 95% Modified Proctor.  He argued that "most" of the soils labs did standard as a matter of course (and the modified was, like I indicated above - a hernia test).  I countered that the use of "modified" - at least to the contractors in our area - tells the contractor that more care is needed in the fill placement and compaction.  I won as I was senior and had to sign off on the report - but this shows that there are good arguments on one side or the other.  It is a matter of experience, personal prejudice, etc.

A guy named Moynihan - a prof at a school in NJ - wrote a damn good book on compaction.  I suggest you get it.

jheidt2543 (Civil/Environmental)
14 Jun 03 10:50
Back to the original question, why 95% vs other percentages.
I have seen a number of specifications with various % compaction specificed for the same job, depending on where in or around the building the fill was placed.  In the "yard" 85%, exterior side of the footings 90%, under footings and slabs-on-grade 95%, pipe trenches under paving 95%.  

We must keep in mind that compaction effort is directly related to cost.  So, require the amount of compaction necessary for the area of use, but don't over specify, it just adds costs.
MRM (Geotechnical)
15 Jun 03 21:04
Great points gentlemen!  When dealing with compaction testing and acceptance criteria, you really need to keep the idea of the statistical density of a compacted fill based on the testing done.  That is, if you get some higher than the specified relative compaction (or relative density in some cases) results and some lower, use of engineering judgement is of great importance when accepting the work completed.  An observational approach coupled with the testing also helps to give a good overall "feeling" that the engineer can use to accept or reject it as well.

jheidt2543 had another important point too regarding the economy of the compaction work-you're wasting money if you try to get 95% relative compaction in landscaping areas-specify a lower relative compaction if the situation permits!

BigH, I'd like to contact you regarding the paper you're talking about.  Even after reading numerous papers on the subject of compaction, there's always something else you can pick up from reading a paper from a new perspective.

As a side note for those who may not know, a very good collection of papers regarding the determination of maximum densities using various methods, field measurement of fill density, and the nuances of estimating strength and settlement properties from the relative density or relative compaction measurements is the STP collection "Evaluation of Relative Density and its Role in Geotechnical Projects Involving Cohesionless Soil" (ASTM STP 523, 1973).  As the name implies, it deals mainly with granular soils.  This is a very well known collection of papers and I've always thought that it should be required reading for every geotech student in a graduate level program or for any practicing geotech engineer involved with signing off on, or specifying compaction work.
BigH (Geotechnical)
16 Jun 03 15:08
Just send your email addresses to the one I gave and I will send out - will start in couple of days.  Moynihan's (maybe spelling is wrong) should be required reading, too.

Helpful Member!  Focht3 (Geotechnical)
18 Jun 03 14:39
I think the fixation with 95% Hernia, er, Modified Proctor has a lot to do with where you started your engineering practice - and what kinds of materials were being placed.  THS (The Hernia Standard) is common among those who cut their teeth in granular soils, while the standard Proctor is more common among those who started out in clay environments - especially where expansive movements are a real problem.  (Overcompacting a CH clay is a quick way to damage a building.)  BigH started out in Ohio, then Canada - so he has a THS fixation.  I started out in Houston - a clay environment - so standard Proctor makes more sense to me.

I think that some engineers get too hung up on the numbers - sometimes I will accept 92% standard Proctor because I'm not concerned about settlement.  But I guess my relaxed attitude - on some projects - has a lot to do with my experience.  Lacking that experience, I would probably do it "by the numbers."

BigH - please send me a copy of the paper also, at your convenience.


cvg (Civil/Environmental)
27 Jun 03 17:56
I think MRM hit it on the head.  The specs are written for "tests" which are done on a limited basis to "control" and "assure" quality.  Statistically, it could be shown that by requiring 95%, that even though you will have areas which are below 95%, they should be within 1 standard deviation of the mean and that should be good enough to prevent failure of the pavement or whatever is built on the compacted soil.  By looking at the cost of the improvement, the design life and the risk associated with failure (including lawsuits for the poor geotech), the Engineer must determine what risk he can tolerate.  Less risk for landscaped areas - 85%, more risk for roads and building foundations - 95%, extreme risk for dams and nuclear power plants - 98% or 100% compaction.
Focht3 (Geotechnical)
29 Jun 03 20:22
I've "run the numbers" on some big jobs - and don't think too much of the statistical argument.  A lot of the variability has to do with natural variability of the soil - not compaction quality per se.

Specifying 95% of whatever standard is usually done "cuz" - that is, "- 'cuz that's the way we've always done it."


BigH (Geotechnical)
1 Jul 03 21:31
Here in India - you specify 95% compaction - as Praydot undoubtedly has ingrained in his head.  Then, for acceptance of a layer, you use the following:


gamma(average) > gamma(spec) + (1.65 - 1.65/sqrtN)*stdev

I tried to get them to change to %Compaction using same formula but they won't.  So you say 95% compaction - then you go and take 95% of it to get the gamma(spec).

So - if your stdev is large (say you get a range of values from 94% to 101% - you can see that the right side gets big - also as more tests are done, it gets big.  Go figure.

Just some info for you all not working here - things are different, for sure.



Focht3 (Geotechnical)
2 Jul 03 11:19
I agree that percent compaction should be used - guess that's what happen when the decision makers don't understand what they are specifying -

The statistical approach makes sense provided the value of gamma(spec) is chosen as a minimum based on some realistic criteria - like a settlement requirement.  But it seems to be chosen mostly due to the "cuz" factor.  So much for real engineering -

BabbageGeo (Geotechnical)
24 Jul 03 0:16
There is another issue here that does not appear to have been considered; that is the moisture content of the soil at the time of compaction and its relationship to the M/C at max dry density for either std or modified Proctor Compaction.  For low moisture content soils, particularly those dry of the optimum m/c or below the m/c at max dry density, dropping below 90% of the max dry density may result in unacceptable settlement and or "collapse" on wetting up.  I suggest you check out the ASCE Geotech Journal Vol 118, No.9 1992, pp1376-1395, "Review of Wetting-Induced Collapse in Compacted Soil" by Evert, Lawton, Richard, Fragaszy and Hetherington.  The paper includes some good references from experience in South Africa as well as the US.

In my experience in typically clay soils in NZ where the soils are generally wet of OMC, using modified proctor as a means of compaction control means burning a lot of diesel drying soil out then compacting it to achieve very little additional benefit.  So std compaction is generally used as the reference, except where low plasticity silts or granular materials are compacted.  Then modified or "Heavy Compaction" is the std.  Given the energy req'd to achieve modified Proctor is more than 4 times that used to achieve std compaction there is usually a significant cost penalty involved in using Heavy Compaction + the risk of setting up unacceptable construction induced pore pressures if the soils are wet of OMC.  The relationship between air voids and density also needs to be considered.  If water needs to be added to reduce teh energy req'd to ensure air voids at std compaction are say always less than 10%, and water is not freely available or is expensive, or the material will rapidly loose strength with the addition of water then reducing the air vodis through the application of "Heavy Compaction" may be the best option.

It is rare that there is not an area somewhere within a fill that does not entirely meet the specification but has passed undetected.  The whole point of testing isthat it is a random statistically based approach to get to 95% or 99% compliance or whatever you chose to try and enforce.  Testing is genearlly carried out to confirm a std higher than required if all fill is unconditionally guaranted to meet a specification to allow for "the one that got away", for variations in soil properties, and post compaction performance under cyclic and or slow increases in moisture content.  The spec should match the post compaction long term load deformation criteria necessary for its intended end use.   
cvg (Civil/Environmental)
24 Jul 03 11:43
collapsible soils are indeed a problem here (Arizona).  not so much for compacted fills, but for foundations.  We have many dams, levees, dikes and other structures founded on collapsible holocene deposits.  It is theorized that upon wetting, the holocene soils may collapse, causing subsidence of the dam and potentially a dam failure.  The solution is to remove the soils and replace them with proper compaction at OMC.
Focht3 (Geotechnical)
24 Jul 03 13:25
BabbageGeo:

Welcome to Eng-Tips!

Collapsible soils (natural and man-made) are a potential problem; they have been discussed in other threads -

BabbageGeo wrote, The spec should match the post compaction long term load deformation criteria necessary for its intended end use.  I agree.  I think that sentence summarized what many of us have been saying in this thread - don't blindly follow a standard without understanding what you are trying to accomplish.



Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

baobab (Civil/Environmental)
4 Nov 03 2:35
Is there an empirical relationship between the various density specifications for soils - Proctor (Standard and Modified) and Mod AASHTO ?
Focht3 (Geotechnical)
4 Nov 03 9:37
A general empirical relationship?  No.  But you can develop one for a particular soil from a given source.  Of course, if the material changes, the relationship also changes...



Please see FAQ731-376  by VPL for tips on how to make the best use of Eng-Tips Fora.

BigH (Geotechnical)
4 Nov 03 14:35
I agree that relationships could/should be developed for your own area soils - then you can be more in the comfort zone - but as Focht3 points out, I grew up on imported granular (crushed limestone) in Ontario and, well - we used to use 97% Modified = 100% Standard as a decent approximation.  (93% = 95%).
Helpful Member!  solutioninc (Civil/Environmental)
12 Nov 03 6:38
This string started with a question on percent compaction for STRENGTH.  I think that is why the aspect of compacting clayey soils to achieve a desired low permeability (hydraulic conductivity to be more precise) was not raised.

Whether it be for the required strength or the required hydraulic conductivity, the proof is in the eating of the pudding.  We have to test samples from the compacted layers to verify that the required property is achieved.  Since this is more expensive than monitoring the density a percent compaction for achieving a uniform layer has been used for a long time.  

As we have different optimum moisture content and maximum density for the two Proctor compaction methods, there is a different OMC and max density FOR THE COMPACTION EQUIPMENT USED IN THE FIELD.  Generally these values lie in between the two proctor values.  But strength requirements dictate compaction dry of optimum and hydraulic conductivity requirements dictate compacting wet of optimum, use of modified for the former and standard for the latter are safe recommendations.  This is because the OMC for the standard test is most likely to be larger than the OMC for the compactor used in the field and specifying moisture content during compaction to be more than the OMC from the test we will be okay.  The OMC from modified test is most likely to be smaller than for the field equipment and so using the modified standard will almost guarantee compaction dry of optimum in the field.  

Regarding the percent compaction one can use either test provided the resulting density is what is required to give the required engineering property.  100 percent standard could be equal to 90 percent modified and so the resulting density in the field will be the same irrespective of the method used.  A series of laboratory tests before writing the specification is the best answer.
Focht3 (Geotechnical)
12 Nov 03 12:12
Hmmm,

While everything that solutioninc is correct, I wonder about the wisdom of focusing on strength as the only "necessary" criteria.  Frankly, I have not encountered a design problem where the strength of a compacted fill was the only design/construction consideration, and the question of post-construction settlement (or swell) was not considered at all.  In my experience, "adequate strength" is pretty easy to achieve in clay soils (LL > 30, PI > 20), but I recognize that others may have had other experiences -

I, for one, was not focused at all on permeability.  In fact, I did a word search on this forum and it appears solutioninc was the first to raise that issue.  In my view, the majority of posters have been clearly focused on the issues of modified vs standard compactive effort, and long term deformation of the fill body.  I think we have pretty much stayed on message during this thread.  (Sometimes the discussion wanders a good bit!)



Please see FAQ731-376  by VPL for tips on how to make the best use of Eng-Tips Fora.

solutioninc (Civil/Environmental)
12 Nov 03 21:34
Focht3 has raised some valid points.  When Proctor came up with a compaction control test way back when, the equipment available for field compaction were relatively light and the Standard test as it was known later (as opposed to modifies) was adequate for the intended purpose, namely compaction control in the field.  With the advent of heavier machinery, the  percent compaction in the field often exceeded 100 and that led to the development of another compaction test with compactive effort 4.5 times larger than the original one.  As of today I am not aware of a percent compaction exceeding 100 if modified proctor is used as the "compaction control" test.  I wrote down all these just to highlight that the percent compaction is not the be all and end all of an engineer's responsibility while constructing an engineered fill.  I just pointed out two engineering properties in my earlier post which the engineer aims for.  A percnt compaction cannot ensure a fill with the required properties simply because the compaction control tests give different maximum densities depending on the compactive effort.  So use of a percent compaction will result in different densities (and therefore different engineering properties) depending on the compaction control test used.  For achieving different engineering properties including those mentioned in my earlier posting and that of Focht3, both the molding moisture content and the resulting density are the important factors.  Also, as mentioned earlier, the standard proctor and the modified proctor lie on either side of the compactive effort of currently available field compactors.  Therefore it is left to the engineer to choose a field compaction control test to achieve his/her objective.  I conclude by restating that one has to do quality assurance tests on samples from the engineered fill to verify that the design requirements are met.  Thease laboratory tests along with the percent compaction data available at a much larger frquency are the ONLY assurance to the engineer of a uniform fill with the required properties.
BigH (Geotechnical)
15 Nov 03 8:28
Maybe what we should be focusing on is not the MDD but the desired void ratio at compaction!  See the article 95% Fixation that I've offered to forward.
Helpful Member!  drfefe (Civil/Environmental)
22 Feb 04 20:59
Hi
Why 95% of compaction of the Standard Proctor like reference for the compaction of grounds were chosen?. In the time that engineer R.R. Proctor invented the logical and practices form to make a compaction, the equipment used in the field was light and was Difficult obtain always the 100% of compaction of Proctor Standard, Besides all the tests did not mach a uniform result. Then the percentage of 95% liked a practical minimum good percentage accompanied with humidity near the optimal of the proctor, At the same time involved an uniformed compaction.  In World War II, started making heavy equipment, and was creating the necessity to establish the test modified Proctor with greater energy of compaction, and continued being conserved the criterion of the percentage of 95%.

Excuse me for my bad English

FEFE
geodan (Geotechnical)
22 Feb 04 21:41
BigH  :) Good lord if you wish to monitor void ratio during fill placement (most moisture-density gauges) then you must come up with AASHTO method of determining the required void ratio for each individual soil type... ahhh!  
incidently in sw washington, for sandy silt/silty sand:  100% of the standard proctor is equal to 95% of the modified as rough numbers.  After many *very* tests conducted on local ML/SM (flood deposit material) we spec 95% of the modified as the contractor usually has no problem achieving +100% of the standard and as somebody said... "stronger is better"

>> silt/sand in our area (avg of many tests)   undisturbed native (1 to 4 feet)= dd 80 to 90, e = 0.9 to 1.2      standard proctor mdd = 95 to 105  17-20mc
   what contractor usually achieves in the field at 14-16mc after approximately 10 passes? = 110 to 115, e = .45 to .6


What is the main reason I dont like 95% of standard?  Even in areas where compacted fill is visibly transfering shear stress (wave motion under loaded dump truck)  generally 24 to 28% mc,  the dd is still 90-95pcf at e = 0.7-0.9  resulting in +95% and adequate compaction according to standard.  Although walking on the ground can indicate "pumping"

Just a bit of my experience with 95%.  
BigH (Geotechnical)
23 Feb 04 16:00
Geodan - I didn't say to monitor void ratio during fill placement but that in choosing the proctor value to which to construct; the void ratio, many times is the desired product of what we want to achieve - it might be reasonable to base your criteria on the void ratio desired.  Send me your e-mail and I'll forward the article to you.
cvg (Civil/Environmental)
23 Feb 04 16:12
Big H

You are correct, when it comes to a flood control dam, levee or other types of embankments that are designed to retain water, maximumizing the in-place density and minimizing voids is a primary concern. Strength is also important to resist deformation caused by earthquakes, but factors of safety are generally large for slope stability.
geodan (Geotechnical)
24 Feb 04 20:23
Yes I agree Big H, I was just being a bit facetious.  As a company policy we have required our techs to record the void ratio (when using the nuclear gauge for fill QA/QC testing) for each test taken as it helps me to review their work.  

However the void ratio varys greatly with the material.  Most crushed aggregate is placed at e = .1 to .2,  whereas the maximum for various poorly graded sand can range from e = .7 to 1.0
Helpful Member!(2)  g7mann (Geotechnical)
6 Mar 04 14:18
g7mann:

This is a most interesting discussion.   My understanding is that the Modified Proctor was developed as a result of an increase in airplane size, weight and undercarriage assembly.   Larger loadings imposed more severe stresses of the fills underlying airstrip pavements and this led to increased damage to those pavements.   The oribinal intent was, i believe, to generarte a "denser" and firmer compacted fill subgrade, and to take advantage of the increasing compactive effort generated by improved compaction equipment.

So much for the origin!   It should also be clearly understood that fill source materials, either imported or in-situ, typically vary in composition, sometimes considerably.   One, or even two or three, Modified Proctor samples will often not generate enough data to "accurately" test all of the placed and compacted fill. Thus, the "requirement" of 95% compaction helps "force" the earthwork contractor to expend reasonable effort to achieve a well compacted, competent and [hopefully] unyilding fill mass.   If the variation in material composition tends to prevent the achievement of this degree of compaction it is always possible to "back off" the 95% requirement providing the contractor is truly exercising his best effort to achieve this goal.   Thus, the 95% requirement is a means of generating a competent fill mass and, given the origin of the test requirement, often a more than competent fill for lightly loaded development, such a residential of light retail.  Practically speaking, the requirement to achieve 95% compaction is a clean and reasonable means of holding an earthwork contractors' feet to the fire.

The "requirement" for this specification appears to me, based onm my more than 35 years experience, results from public agency pressure.   Many, if not most, public agencies make this requirement in an effort to cover their liability [real or percieved] and do not understand what this means in time, effort, cost,or even result.   They are tied to having paper test results just so thay can point at an engineer or technician and say "they said it was ok."    Although a generalization, many public agency employees do not understand the reasonaing behind fill compaction, or wahy variations in the results [degree of compaction achieved] means.   As a result the achievement of 95% of Modified Proctor compaction is ultimately often a paperwork exercise.

Also, and this is a pet peeve of mine, virtually none of the technicians I have been involved with have ever plotted the laboratory proctor test curves as  "family" on a single sheet.   Typically, the technician is provided with an optimum moisture content and a maximum dry density and he [or she] simply inputs this to the nuclear density gauge and goes merrily on his [or her] way.   This does not work.  I typically insit on haveing a family of curves plotted and then have the technician plot ever field density test on this family of curves.   This will immediately show which of the test curves the tested soil meets [or does not] and will provide a more accurate indicator of fill densification.   Many times I have been required to explain to a contractor why the field tests indicate a "failing" result [<95%] but the compactor is bouncing on the fill surface and is shaking the adjacent houses.   It is generally because the technician only has the numbers for a material, and that the material being tested in the field is not the material tested in the laboratory.   Well, that's off my chest for now.

Lastly, the achievement of any degree of compaction is determined by the soil composition [particularly the percentage of silt and clay fines], the materials' moisture content, the amount of compactive effort being imposed on the fill mass, the thickness of the layer being compacted, and the suitability of the compaction equipment.   Ultimately, if all of the above is taken into account, regardless of the specified degree of compaction, the end product should be  a firm, competetn and generally unyielding fill mass.

Focht3 (Geotechnical)
6 Mar 04 23:26
g7mann:

Welcome to Eng-Tips!

I agree with you - but the technician's ignorance on this point isn't all bad.  I customarily input the results into a spreadsheet to calculate the apparent degree of saturation as well as allow me to plot the results.  "Outliers" have a habit of occurring when techs "pencil whip" results to satisfy the contractor.  (They're not smart enough to adjust both the water content and density; they usually only change the reported dry density.)  Sometimes it's a crooked tech, sometimes it's a sense that the test result is wrong.  But it doesn't matter why; it's a clear warning that a particular technician - or job site - bears closer scrutiny.

Keep posting - your experience is a real asset.  Again, Welcome!



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.

BigH (Geotechnical)
23 Mar 04 18:07
Seldom, too, does anyone ever plot the ZAV on laboratory compaction curves.  This can get you trouble if your field results are "on the wrong side."  Happened to a very very reputable firm.
Focht3 (Geotechnical)
23 Mar 04 21:42
Yup.  Yet it's so easy with modern geotechnical software...



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.  See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

dirtsqueezer (Geotechnical)
24 Mar 04 3:12
baobab,

Just picking up some of the table-scraps here.  I've run both density specifications for soils using the modified proctor, and found some differences that I think affected our work.  

On an FHWA project for a summer I performed the mod AASHTO where I had previously only used ASTM D1557 in the company lab.  The method uses the same weight, drop, and basic moisture distribution (though different soil types for different weights, actually), the major difference being that the AASHTO method re-uses material from previous moisture points for subsequent moisture points.  The ASTM method specifically prohibits this.  I happened to be working near Mt. St. Helens at the time, and tested a good amount of native fill that consisted lightweight pumice.  You can imagine how ground up that component was throughout the course of testing.  I actually ran a few ASTM D1557s for comparison (because there was no one else there to tell me not to :), and consistently got up to 2-3% lower numbers using only pristine samples with the porous rock intact.  I'm not sure how the pumice would have reacted in actual lifts in the field, but it seemed to me at the very least debatable.  

Another difference was  the grain size division between the 12" and 18" drop methods, though I don't remember thinking results would have been affected.  Also, I think there was a minor difference in the accounting of oversize material.  One method of the AASHTO I believe specifies complete removal of oversize w/o adding it back in.  I have both methods, and would have to go back and be sure, but I could get more specific in the wording, if you're interested.  

Also just interesting to note with the pumice fill, because of the extreme low specific gravity- actually less than 1 (the rock floated), an oversized rock correction would have actually dropped the proctor value!  That is, again, assuming again the rock wasn't ground up during compaction.  We didn't happen to have that much larger pumice in our soil, but it was fun to consider.  
Focht3 (Geotechnical)
29 Mar 04 18:45
An excellent point!  It's important to remember, too, that all of our basic tests (consolidation, unconfined compression, direct shear, pressuremeter, DMT, CPT, etc.) assume that the soil grains are incompressible - which is debatable (or outright wrong) when dealing with oolitic sands and some volcanic materials.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.  See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

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