×
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

Consolidation test on silt

Consolidation test on silt

Consolidation test on silt

(OP)
Hello experts,

I started running a consolidation test on a silt (MH).

It's qu = 400 kpa (8000 psf).

This sample is 40' deep. It's overburden pressure is approximately 190 kPa.

As per ASTM D2435, when running the consolidation test, you are supposed to start with small load increments (5 kpa, 10 kpa, etc), keeping a delta P/P = 1.

In my case, i started with 5 kpa increment load and noticed the dial indicator hasn't moved during the first 6 readings (0.25 mins, 0.5 mins, 1 min, 2 mins, etc).

Then I doubled up the applied load (10 kpa) and noticed the same behavior.

The question I have is:

Is this behavior due to such small load (5 kpa - 10 kpa compared to a qu = 400 kpa) or because it;s overburden pressure is way greater than the first load increments??

If this continues happening, I will continue increasing the load until some deformation behavior can be read. The problem is I don;t want to add such high load ad once that could damage the soil sample.

Please let me know,

Thanks in advance.

RE: Consolidation test on silt

Well if you have Su of about 200 kPa, that is quite a stiff clay and I'd say that your overconsolidation ration would be in the order of 4 or so.  So you have a long way to go to get to it . . .  I know that you say you have a MH soil - what are the Atterberg limits?

RE: Consolidation test on silt

(OP)
Big H,

Thanks for your reply. This are the atterberg limits:

LL = 60%, PL = 20%, IP = 40%.


What do you think?

RE: Consolidation test on silt

I'm agreeing with BigH - very stiff silt!  What's the natural moisture content?

f-d

¡papá gordo ain't no madre flaca!

RE: Consolidation test on silt

(OP)
thanks for your reply.

The moisture Content is 43%.

RE: Consolidation test on silt


I agree with BigH and fattdad.  The moisture content is almost halfway between PL and LL.  Considering this and the Su of 200 kPa, you are definitely dealing with overconsolidated soil.  My estimate is OCR between 3.5 to 5.5; therefore, what BigH noted above is spot on.  However, this all assumes that your sample was saturated (or close to saturation) when conducting the shear strength test.  If the soil is not saturated, all of these discussions are not applicable. With the natural moisture content of 43%, I believe this sample is below groundwater table and therefore, saturated.  

In respect to readings, you are not going to get much movement on the small loads, particularly in silt.  I expect the Cr to be lower in silt than a clay with similar LL
 

RE: Consolidation test on silt

(OP)
Guys,

Thanks for your imputs.

So far, I have added the 5th load increment (around 272 kpa), and yet I haven't experienced any deformation.

FYI,

I am using an arm ratio of 11:1. So far, I have added 8 kilograms. This consolidometer can support a max weight of 88 kgs. By keeping a delta P/P =1, probably I will be able to add 3 additional load increments. Other than that, I will try to run the test on a higher capacity consolidometer.  

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