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Engineered Fill Question?

Engineered Fill Question?

What is the difference between "Engineered Fill" and for lack of a better term regular "Dirt"?

RE: Engineered Fill Question?

Engineered Fill has known gradation and properties.
Compaction can be obtained more efficiently and evenly because of the gradation.

While testing can determine the properties of your "dirt" there is always a need for stable fill, which will act the way you need it to act.

RE: Engineered Fill Question?

How is the "Known Gradation" it not through tests or seive analysis? And is an entire stockpile of engineered fill scrutinized/tested or are samples taken at a particular frequency?

RE: Engineered Fill Question?

Engineered fill has much to do with the placement and compaction of the material you are using and not just the material itself.

You can use any type of material from granular material to silts and clays for engineered fill provided you have the willingness to place it properly. Quite often the use of on-site existing fills or "dirt" is not suitable due to the variability of the material, debris, organics, garbage etc.

Types of material testing and test frequency depend a great deal on the type of material and source of the material being used as engineered fill.

Placement of the engineered fill materials is typically controlled and involves certain thickness of the material placed and proper compaction of the material.

Contrary to popular belief engineered fill is not necessarily a cure all for all sites. You may get too much settlement of soft subgrade soils. You will always have some settlement of the engineered fill.

Confer with a geotechnical engineer prior to proceeding. Too often the call is made after all the so called engineered fill is placed. When this is the case the so-called engineered fill can be considered dirt and may have to be restarted all over again.

RE: Engineered Fill Question?

rahseanj wrote:

How is the "Known Gradation" it not through tests or seive analysis? And is an entire stockpile of engineered fill scrutinized/tested or are samples taken at a particular frequency?

These answers are typically spelled out in the project specifications.  

It is not clear if you are reviewing someone else's design or developing your own design.  If someone else's, then find the specs for the fill.  If your own, then consult a geotech to help you write an appropriate spec for your site application of engineered fill.  Also, many Dept of Transportations will have a standard spec for this sort of material, although it may not be called "engineered fill".

RE: Engineered Fill Question?

to put it a little more succinctly, engineered fill is furnished and placed to meet the engineers requirements for the specific use.  This may include requirements for the type of material, gradation, plasticity, permeability, compaction, moisture content, placement methods, QA/QC etc. which are often published on the plans or in the specs.  It is usually tested, inspected and as-built.

Non-engineered fill is not designed or specified by an engineer and the embankment does not usually get inspected or tested for quality control.  Hard to tell what you will get with non-engineered fill or if it will be suitable for the desired use...

RE: Engineered Fill Question?

Thanks for all the help guys that is very helpful.

But to explain my situation, I am helping inspect the placement of fill at a site. The contractor was attempting to use the native soil but couldn't consistently achieve the required compaction percentage and was forced to remove what was placed. A different material was brought in from off-site but the contractor says it is non-engineered fill (or dirt).

I would just like to know:

How you determine the material is homogenous throughout the entire placement process?

How an off-site material is not considered engineered fill?

Does the type of compaction equipment and the number of passes matter if you achieve the require moisture content and density?

RE: Engineered Fill Question?

I've had trouble with the term "engineered fill".  There is some confusion in the industry (or at least in NC) about what it means.

If a suitable soil type for structural fill passes the gradation analysis and any other soil requirements specified and is placed and compacted properly, should it not be "engineered fill"? I believe the posters here agree with my take on it.

Apparently, we're wrong.

Here is what I've deduced are the requirements for "engineered fill" according to people I've met in the field, and since i've had to communicate with them, I've adopted it as well (after i've seen the soil on-site, of course).

In piedmont and coastal North Carolina, "engineered fill" must
1. come in a truck from a quarry
2. at the quarry the material was graded by adding different materials of uniform gradation together and mixing. (perhaps this is the engineering of it? done by bulldozer engineers!)

The "engineered fill" i've seen has been a sand mixed with small crushed gravel.

The point of this post is that there may be an engineering language issue and it may have a regional aspect to it. Your "engineered fill" might not follow the rules i set or it could be like oranges and apples if you compared a bucket of ours verses a bucket of yours. I prefer to talk in terms of "structural fill" since most people agree on its meaning.  The "engineered fill" i've seen has one engineering property that most SOILS don't (let's agree not to call it dirt either, such a dirty word) and that is that water infiltrates very fast if it has somewhere to drain to.
But the drainage aspect could very well be specific to our apples.

hope this doesn't confuse it,

RE: Engineered Fill Question?

Quote (rahseanj):

How you determine the material is homogenous throughout the entire placement process?

You will have to test the borrow material to determine if it's properties are acceptable.

Quote (rahseanj):

How an off-site material is not considered engineered fill?

If it meets the specifications and QA/QC and is accepted by the Engineer, than it is "engineered" - regardless of what your contractor says...

Quote (rahseanj):

Does the type of compaction equipment and the number of passes matter if you achieve the require moisture content and density?

Probably doesn't matter, but a good question for the geotechnical engineer

RE: Engineered Fill Question?

Engineered fill - if the fill moisture conditioning, placement, and compaction is observed and documented by a credible engineering firm, and an appropriate number of field density tests and laboratory tests (material specification compliance and compaction) are taken and the fill material and completed fill meet specification, then I'd suggest the fill is "engineered."  With this information you can make an informed estimate of the material's engineering properties, and then estimate how the material will perform under design loads.


RE: Engineered Fill Question?

Here is a scenario...A site is being built near an ancient landslide and in order to build at that site the landslide material or "dirt" must be made structurally sound.  I have done this by removing the the lower portion of the landslide and building a buttress at the base of the landslide to support it.  Now mind you the material used to support the landslide came from the landslide itself.  it was in a loose state as it had obviously been disturbed.  That material was compacted in place per the specified moisture and compaction.  So the same material can be both dirt and engineer fill.  

RE: Engineered Fill Question?

No fill is homogeneous.
Variation in the fill affects its engineering properties.
Suitable testing is needed to document the as-placed condition.
In the absence of suitable testing the completed fill is unknown.
As a result, you may not be able to depend on its engineering properties.

Hope this helps.


¡papá gordo ain’t no madre flaca!

RE: Engineered Fill Question?

The term engineered fill derives from the US but is spreading world wide. Structures that I would never previously have considered constructing on fill can now be easily constructed by using Engineered Fill. Simply describe the fill on the drawings as Engineered Fill and show it in cross hatch. I can now construct reservoirs partly in cut and partly on fill using Engineered Fill without any fear of differential settlement.  It is a brilliant multi purpose not compressible, inert material that solves all your foundation problems. Where you get it from I have no idea.

RE: Engineered Fill Question?

i detect a note of sarcasm...

RE: Engineered Fill Question?

oh great, now i've another urban myth to contend with on top of dealing with "self-compacting #57 stone"...

RE: Engineered Fill Question?

CVG - I agree with what you say - It is fill (or should be) that is selected, processed, if necessary, placed and comapcted to meet some specified end result performance tests and is thereby fit for purpose. It can be local dirt compacted with the back of a spade if that produces the required performance to an assured quality.

RE: Engineered Fill Question?

I know a grader who has been getting ripped off.  He buys 90% Proctor compaction fill from the quarry for the price others are paying for 100% Proctor compaction fill. blllttt

RE: Engineered Fill Question?

he must've seen the "for sale" sign out in front and misunderstood the "10% off"...

RE: Engineered Fill Question?

ok guys, when I read engineered fill within a specification, inmediatelly understand that geotecnical engineer need a fill material that meets certain features to be suitable to withstand structural loads, so, as fatdad posted, fill material properties are variable specially if these materials come from a borrow pit, therefore, in order to mantain reasonable homogenity, certain restrictions are given by the enginer, for instance, typical engineered fill characteristics are (it may vary from project to project or agency):

Natural or artificially graded mixture of natural or crushed gravel, crushed stone and or crushed sand with a least 90 percent of material passing 38 mm (1-1/2 in.) sieve and not more than 12 percent passing No. 200 (0.075mm) sieve

sometimes a maximum LL of about 40 and a PI not higher than 12 is specified.

So, if you see this material is quite specific and it is easy for someone with certain CMT or Geotechnical Trainning to identify this materials at the jobsite
In the other hand, it is not just the material characteristics, engineered fill involves placment controls, thickness should be surveyed, moisture content should be within a certain range, and a minimum percent of the maximum density should be reached.

by the way, engineered fill is not a magical solution and certain conditions should exist to use it to built something on it and geotechnical engineer based on some theories and experience determine if it is a suitable solution, who could imagine that colum stone could work  simply drilling a hole in soft soils and filling the hole wit gravel, and it realy work.  

RE: Engineered Fill Question?

Stone columns are usually constructed with holes made by vibrating a mandrel.

RE: Engineered Fill Question?

Isn't engineered fill just any fill that is to be placed for an engineering purpose, ie. building pad, road bed, dam, ect?  Not that I'm proud of it, but I've had engineers from my company approve just basic silt for a regrade, I believe it was for a set of apartment buildings.  I didn't do any of the testing, so I'm not sure how that came out; hopefully it wasn't wintertime.  I think trench backfill wouldn't necessarily be engineered, being that is just somewhere to put the dirt back after you've dug a hole, not that it shouldn't be compacted.  In my experience, engineered fill is fill to be used for an engineering purpose, all properties aside.  

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