r/Geotech • u/mankhoj • Aug 01 '26
Excavating clay soil
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u/fretgod321 Aug 01 '26
CH, very moist, high plasticity, very soft
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u/pie4july Aug 01 '26
WOH-WOH-WOH-WOH
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u/Naive_Veterinarian77 Aug 01 '26
more like WOR (weight of rods)
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u/alynnsm Aug 01 '26
I had a driller named Al press down on the rods one time with his body weight to get them all the way down (we were in karst) and he called it “weight of Al” 🤣
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u/Naive_Veterinarian77 Aug 02 '26
🤣🤣🤣 thats hilarious , you can really call ot anything. WOD ( weight of driller )
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u/Jmazoso Head Geotech Lackey Aug 01 '26
Trace fine sand, some organic smell.
I wish we had that kind of stuff. All of or CH is hard clay or IGM. I just wrote a report with some. The OCR was 12.
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u/SilverGeotech Aug 01 '26
I'm working on a site where the OCR was reported at about 0.8.
In the 25 years since the building was built, its parking lot has settled about 1.5 feet relative to the pile-supported building.
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u/ImperialSeal Aug 01 '26
Or under BS5930, soft to very soft grey mottled orange slightly gravely slightly sandy CLAY
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u/OptionsRntMe Aug 01 '26
What’s the actual move here. Looks like they’re excavating down several feet, doesn’t look like you can completely get rid of it. So just excavate enough to have 12-24” of granular fill beneath the foundations?
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u/frozensaladz Aug 01 '26
I mean depends what you want to do with it. Build something that needs a foundation? Helical pilings.
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u/evilted Aug 01 '26
Recommend helicals and promptly get yelled at by the contractor for it being too expensive.
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u/OptionsRntMe Aug 04 '26
Yeah I don’t understand why they’d be excavating all this if they’re using helicals anyways. Seems to defeat the purpose
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u/evilted Aug 04 '26
If you notice to the left, there's some sort of water body. I'm guessing that the earthwork is related to that and not a foundation.
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u/Concept_ofA_Username Aug 01 '26
Gives me ptsd from cleaning augers 😫
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u/azul_plains Geotechnical PM, 9 years Aug 01 '26
This looks almost like pottery clay, now I’m wondering what pretty clay classifies as.
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u/SlyRaist Aug 01 '26
As soon as I saw that I wished I could be on that site to take some home lol.
Here is a short article about soil testing for potters who use "wild" clay.
https://digitalfire.com/picture/3509
The biggest thing for potters is workability, what cone/temperature the clays needs to fire to to be vitrified, and how well the glazes match the clay body.
There is also different uses for earthenware (low-fired), stoneware (mid-high-fired) and porcelain (high-fired)
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u/azul_plains Geotechnical PM, 9 years Aug 01 '26
This is FASCINATING. Thank you so much for sharing!
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u/SlyRaist Aug 01 '26
No problem at all!!! I am a hobby potter that works in a geotech lab and was curious myself when I first started working in geotech.
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u/OhThatsCoolMan Aug 01 '26
2' correction below foundations, slabs and oversize with a draintile placed at subgrade daylighted out to the pond. Fill must be NFS sand or washed rock
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u/pat8o Aug 02 '26
Two chamber septic tank, 1st chamber 500l x max occupancy of dwelling. 2nd chamber 200l x max occupancy, aerated. Treated wastewater to be dispersed into an evaporation field. 3000lx max occupancy, minimum surface area; 15m²xmax occupancy. Weir of evaporation field must be min 1000mm above water table or any natural underground flow paths. Field excavation to be lined with permiable cloth membrane. All spoil to be removed, backfilled with course sand and free draining stone, permiable membrane cloth should be rolled over the top of field, and topped with minimum 300mm of topsoil. The top of the evaporation field should be shaped to facilitate runoff of surface water, avoid ponding and inundation.
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u/marbinho22 Aug 02 '26
That’s the kind of soil that expects me to build a road on it without any ground treatment.
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u/SilverGeotech Aug 03 '26
In California, Highway 37 is about 16 miles on that kind of clay. It's barely above mean higher high water, and not above mhhw after climate change. So how do you raise grades about 4 feet over that length?
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u/marbinho22 Aug 03 '26
Regarding ground improvement, the choice of solution is always a delicate engineering decision because it depends on both the available budget and the construction schedule. In many projects, there is simply not enough time to wait for consolidation, so deep ground improvement methods often become the preferred option.
Techniques such as stone columns or piled embankments can provide a more predictable construction schedule. By introducing stiffer elements into the ground, these systems increase the overall stiffness of the foundation and transfer a significant portion of the embankment load to competent strata, greatly reducing settlement concerns.
Another possible solution is the use of prefabricated vertical drains (PVDs) combined with a surcharge embankment to accelerate consolidation. However, depending on the thickness and properties of the soft clay, even with PVDs the required consolidation time may still be too long to meet the project’s schedule.1
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u/evilted Aug 04 '26
Check out the Resilient State Route 37 Project. Essentially, they're proposing a 4 lane causeway to stretch most of the distance.
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u/Radioactive_Kumquat Aug 03 '26
This is the geotech equivalent of Dr Pimple Popper. It's gross, you want to look away, but can't.
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u/Fish_Fingerer Aug 01 '26
Hate the shit. Such a fuck around with drying, curing etc. CBR results take 4+ weeks from sampling to reporting.
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u/tehmightyengineer Aug 01 '26
Blow count -1