Select Fill Materials 5

[ONENGINEER]

Could someone help me in understanding the term "Select Fill" materials. I understand these fills are not expansive and can substitute the expansive soils in order to decrease the potential vertical rise of the sub-grade soil due to moisture variations. What are the typical ingredients of select fill materials. I presume they are sand and clay. How many percent clay do they have? Thank you.

 

[JedClampett]

We have a standard specification for Select Fill. I think it's defined as a granular material with no material than can't pass through a 3 inch sieve and a PI less than 15 (maybe 30). If the Geotechnical Engineer has a different definition we adjust this.

 

[SlideRuleEra]

Where I work, "Select Fill" is a general terms that means the best locally available material for the intended purpose. If the specification gave ideal properties, the material may have to be brought in from a long distance away (say, > 100 miles). Not cost effective... unless absolutely necessary.

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[fattdad]

select fill is defined by our specifications. Our specifications are likely consistent with the FHWA.

f-d

ípapß gordo ainÆt no madre flaca!

 

[oldestguy]

Usually is is granular material with no plasticity (very little if any silt or clay). A common material is that used as fine aggregate for concrete.

 

[Ron]

As others have alluded, "Select Fill" is not a clearly defined term within the profession and depends a lot on what is available at a particular site as SRE notes. In my area, "Select Fill", presumably meaning "Select Structural Fill" is generally taken to mean relatively clean fine sands having less that 10% passing a No. 200 sieve, non-plastic and having less than 5% organic loss on ignition. In other areas, that specification will change depending on the nature of the materials available.

 

[ONENGINEER]

Thanks for all enlightening answers. This is related in a project in North Texas. The select fill has a PI of less than 15. But the gradation is not available. For soil expansion analysis,I require the typical percentage of clay in the select fill. I wonder if someone can provide me an answer to this as well. Thanks.

 

[cvg]

select fill or select material is locally defined and generally project specific. It will be different if this for use in a landfill, structures, landscaping or for road construction. For instance, landfill select fill would be lean clay, clayey sand or clayey gravel. Structural select fill would be GW, GP, SW, SP with low PI. you will need a sample of the proposed material if there is no spec. However, with a PI less than 15, I would assume that the percent clay would be need to be very low

 

[fattdad]

is it a highway job?

f-d

ípapß gordo ainÆt no madre flaca!

 

[fattdad]

(search this document for select. FHWA calls it select borrow and provides a description.)

https://flh.fhwa.dot.gov/resources/specs/fp-14/fp14.pdf

f-d

ípapß gordo ainÆt no madre flaca!

 

[ONENGINEER]

Thanks fattdad and cvg. The select fill in here's context is for replacement of usually top expansive soils to reduce the heave of footings due to seasonal moisture changes for low rise structures. It has similar application in roads and highways. The FHWA did not have any any item on this when I carried out a word search. Maybe it is more of the states rather than federal scales. E.g. TX LA, CA, ..

 

[Okiryu]

ONENGINEER, Here are some documents related to earthwork specs and guidelines for expansive soils for DoD projects. However, I have not read the expansive soil related document as we do not have expansive soils in my area...anyways for your reference.

https://www.wbdg.org/FFC/DOD/UFGS/UFGS 31 00 00.pdf

https://www.wbdg.org/FFC/DOD/UFC/ARCHIVES/ufc_3_220_07_2004.pdf

 

[Doctormo]

I agree that the terms "select fill" and/or "structural fill" have different meanings across the US as noted above. In areas where expansive and fat clays are common and granular materials are not, select fill may be a clay of low expansion/plasticity. In these areas it is necessary to call a material "select granular fill" if that is desired and provide the appropriate specifications

As an example, if one has an highly expansive foundation material, removal and replacement with compacted lean clay may be a better solution to keep water from the expansive soil foundation than sand as an example. Usually a LL and PI requirement would be specified and possibly expansion/swell testing to confirm that the material does not have the same problem as the material being replaced.

TX, CO, KS, MS all have their issues with expansive & fat clays so I would look in those areas for local standards of practice regarding foundation treatment in expansive soils.

 

[ONENGINEER]

Thanks Doctormo for letting me know which states have expansive soils. The information I received from all respondents were useful and conclusive and thanks to all.

One more aspect of expansive soils that I have been looking for is the estimation of uplift pressures on the bored pile's skin, when the dry soil swells. I very much appreciated a feedback on this subject, too, if possible.

 

[aeoliantexan]

I work in North Texas, and our earthwork specs include a section on earth fill classifications. For select fill we commonly specify Class 4 Earth Fill, defined as SP, SM, SC, CL, or dual classifications thereof, which have a liquid limit less than or equal to 35 and a plasticity index of a minimum of 4 and a maximum of 15, which are free of organic materials.

This may have some swell potential, but much less than the CH it may be replacing. Materials used are often sandy clay or clayey sand.

We will amend the specification to meet the particular needs of the project.

 

[fattdad]

I'm afraid the OP has missed my point, so I'll restate it.

On a project with federal DOT funding, there is a likelihood that, "Select Fill" is as defined by the FHWA. I've provided that link. On jurisdictional or private projects, I'd agree that there is local convention that may allow such select fill to include USC classifications, CL, or ML, or other? Clearly in private practice, the specifying engineer can define it at will. Nobody in DOT work would defer to such local custom; however, as the FHWA definitions would prevail.

f-d


ípapß gordo ainÆt no madre flaca!

 

[ONENGINEER]

aeoliantexan, I wonder if I should start a new string or you could kindly let me know how you choose the uplift pressures on pier footings. I have seen 0.5 to 1.1 tsf but wonder on waht base they are recommended. Thanks.

 

[aeoliantexan]

I haven't done much of this. I think it is pretty common local practice to assign about 0.5 tsf upward skin friction to the pier through the seasonally active zone of expansive soil. One would expect that this would vary with the strength of the material, but apparently it is conservative enough. I will check with some of my associates.

 

[ONENGINEER]

aeoliantexan,

I am still looking for the uplift pressure estimation - theoretical or empirical values. Das textbook has a section on this but it is complicated and I guess overestimates.

 

[Okiryu]

ONENGINEER,Look at page 2:

http://web.mst.edu/~rogersda/expansive_soils/Various Aspects of Expansive Soils.pdf