USDA Soil Textural Triangle 4

[cap4000]

When using the textural triangle you can only plot clay, silt, and sand. What happens when you have say 10% gravel?? Am I to remove all gravel and redo the sieve analysis?? Any tips will be greatly appreciated.

 

[fattdad]

What's the end game? Are you designing a drainfield, evaluating the soil moisture characteristic curve or what? If you are working on an engineering project, I'd encourage you to use ASTM or USC methods rather than the soil classification method developed by the U. S. Department of Agriculture.

Just an opininated engineer. . .

f-d

¡papá gordo ain’t no madre flaca!

 

[escrowe]

I believe the USDA standard requires mathematically replacing the gravel material.

 

[iandig]

I thought that the gravel was reported seperately. We only tend to use this figure [in the UK] when we consider topsoil and subsoil, and any material greater than 2mm is reported as the 'stone content' with further reference to 'size of stones'.

 

[Unotec]

I think the answer to the OP's question is Yes. Remove the gravel, do the sieve analysis and report separately.
What the soil is wanted for will give significance to either or both reports

<<A good friend will bail you out of jail, but a true friend
will be sitting beside you saying ” Damn that was fun!” - Unknown>>

 

[escrowe]

I have reported such verbal classifications as 'gravelly sandy loam' or 'sandy loam with gravel,' that sort of thing.

The point is that the gravel fraction (above say 10 percent)
is not treated as sand for the purpose of classifying the soil on the textural triangle,
or subsequent characterization of the permeability (infiltration rate)
or hydraulic storage capacity of the soil.

 

[dirtguy4]

I would say no..........by removing the gravel from the sample, you are changing the soil. The gravel portion is part of the soil matrix.........unless they will be screening the soil through the 4.75 mm sieve prior to placement or it's intended use.

For example you have 10% gravel, 45% sand, 25% silt and 20% clay..........it plots on the soil triangle as just that.....45% sand, 25% silt and 20% clay.........if the 10% gravel makes it impossible to plot then I would maybe convert the gravel into sand......but I think if you are using the soil triangle correctly it takes in account gravel sizes and the fact that 100% of the sample is not always sand, silt and clay.

 

[rockchip]

From soil science, the percentage of gravel in a soil matrix causes a proportional increase in the bulk density of the soil while causing a proportional decrease in the saturated hydraulic conductivity. Hope this helps.