SPT sampling and logging fill materials
SPT sampling and logging fill materials
(OP)
I'm a newbie to the forum! I've always had some difficulty interpreting the difference between fill materials vs. native soil materials when performing and logging SPT tests. I will appreciate people's thoughts, opinions, experiences and any online references/presentations addressing this matter. It is sometimes not as easy as it may seem. Is there anything specific to watch out for as far as soil fabric, contents, etc. inside the spoon?
Thank you for reading and for your interest.
Thank you for reading and for your interest.





RE: SPT sampling and logging fill materials
RE: SPT sampling and logging fill materials
RE: SPT sampling and logging fill materials
Natural soils at shallow depth may have roots in place, worm holes, root holes, or thin stratifications etc that tend to get smashed shut or disrupted during placement of fill.
Loess and some alluvial soils may have root holes that tend to be predominately vertical. In fill, the root holes may be closed up or going in random directions.
Poorly compacted fill may have visible clods. Compacted fill may have sheepsfoot roller impressions you can find.
Fill often has a mixed-up quality, especially random mixtures of color, whereas natural deposits have a more uniform appearance.
Someone will laugh, but I find that when you dig into some natural soils, say silty clays, there is a "crunchy" feel and sound that doesn't occur in fill. Think of biting a Kit-Kat bar as opposed to a Milky Way. I attribute it to a weak cementation that develops with age.
Finding a gum wrapper or pop can helps too.
In short, you are right, it is not always easy, and what helps in some soils doesn't help in others. It is an art worth developing, however.
RE: SPT sampling and logging fill materials
I always look at the site grading, sometimes its obvious an area has been filled. If there isn't a topsoil layer under the fill, there is usually a colour change. The fill will be darker, and often the SPT counts will jump bit after the colour change. The senior guys in my office always break split spoon samples to look at how the soil structure breaks. I think the idea is that fill is very disturbed and usually won't break with smooth planes or other structure. They also smell the soil a lot. I don't know what for. They also look for rocks that don't belong, either shape or type. Often fill will contain little bits of organics which don't belong at at that depth. If I'm not sure, I still have a descriptive log and a sample for someone else to look over.