×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

USDA Soil Textural Triangle
4

USDA Soil Textural Triangle

USDA Soil Textural Triangle

(OP)
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.

RE: USDA Soil Textural Triangle

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!

RE: USDA Soil Textural Triangle

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

RE: USDA Soil Textural Triangle

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'.

RE: USDA Soil Textural Triangle

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>>

RE: USDA Soil Textural Triangle

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.   

RE: USDA Soil Textural Triangle

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.

RE: USDA Soil Textural Triangle

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.  

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources