Diference between BACKFILL and SELECTED FILL MATERIALS 10

[Antonio Mussual]

Hi Geotechicals. May someone tell me the difference between these concepts:

Selected Granular Material
Selected Fill Material
General Backfill Material

Thanks in advance

 

[BigH]

It's all how they are defined in the Specifications. Selected Granular fill could - or should - be considered as "engineered" fill onto which you can place foundations (subject to). I would say that selected fill material would be fill with some restricted properties such as percent of fines, plasticity and that - might carry light loads and could be material that is placed as fill behind retaining walls (excluding the need for filters). General backfill material is probably "earth" fill that is used to raise grade, say, in landscaping areas or so - but onto which no foundations or loads will be imposed.

I prefer to be more specific - in Ontario, they have specific material designations (such as MTO Granular A, Granular B, Granular C and the like). Specifically define what you expect of the fill if you use one of the terms you posted.


If one leaves "vernacular" terms like you proposed, Contractors will be smiling all the way to the bank - they will throw in whatever they can find, the Engineer will say no - but the Contractor will say - there was nothing defined that made what I want to use unacceptable - and fights will ensue with monetary implications.

 

[Ron]

Yes...BigH knows what he's talking about. Pay attention!!

 

[Settingsun]

On the other hand, don't reinvent the wheel. If you've come across those terms, they may be common in your area with supply readily available. Eg from Australia:

 

[JedClampett]

We get our information from the Geotechnical Report. What one Geotechnical Engineer calls Select Structural Fill, another might call Processed Native. And I try to match the Report directions as closely as possible. So from one project to another the definitions will likely change. We therefore have one specification that defines the materials called "Soil and Aggregates for Earthwork" which is referenced into our "Earthwork" specification.
Is it perfect? No. But if we dot our i's and cross our tees, we can get a design that matches the Geotechnical Report.

 

[sdz]

General backfill would probably be site excavated material without any particular specification; what ever you dug out you put back.
As others have said there should be a specification for select fill,either for the project or in a standard. Requirements can vary depending on the project.
As general descriptions;
Selected Granular Material = a non cohesive material such as sand
Selected Fill Material = can contain cohesive material but probably a non expansive soil.

 

[LittleInch]

I know this the foundation forum, but for something like pipelines, the general definition would be

Selected Granular Material - Something like clean sand (without fines), gravel or something that allows movement

Selected Fill Material - General backfill material (i.e what you dug out of the ground to make the trench, but filtered / sorted to remove "deleterious material), i.e. plant based things, wood, sharp rocks, concrete, rubble, flints etc. Sometimes called "Intimate fill" to surround the pipe or cable for about 300mm before you use general backfill.

General Backfill Material - What you dug out of the ground to create the trench / hole.

But sure, foundations are a bit different and get a bit more specific.

I love the way the AS spec noted above has seemingly converted from a nominal imperial size (2", 1 1/2" etc) to precise metric units. Nuts. Should be 50, 35, 2 or maybe 2.5....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Settingsun]

The Australian sieve sizes are based on reductions from 75mm. 53mm = 75/sqrt(2), 37.5 = 75/2. 2.36 results from further successive halving.

 

[Antonio Mussual]

Thank you guys. Your comments helped me a lot.
Actually Iam from Mozambique (Southern Africa), and here we do not have local geotechnical standards and codes as we are supported by Portuguese standards and codes, unfortunately.
What could be different here is the codes that you use but it was possible to get the main idea about these terms.

Note: do not pay to much attention on my bad english (grammar and so on), I'm a english learner.

 

[Waseem Raja]

Any material removed during site excavation, without regard to precise specifications, would likely be used as general backfill; whatever you dug up, you put back.

Select fill should be specified, either for the project or in a standard, as others have mentioned. Depending on the project, requirements can change.

you can find here in more detail about Backfill, Select Fill Fill or Granular Fill Material with Specifications
Backfill, Fill, Select-Fill and Marl Cap Materials Specifications