×
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

Fine grained soil Behaviour based on permeability

Fine grained soil Behaviour based on permeability

Fine grained soil Behaviour based on permeability

(OP)
Greetings to all.

The project location is majorly dominated by Sandy SILT with very less clay content (ML-CL). Silt is everywhere more than 55% and clay is less than 18%. The direct shear tests (DST) shows a C-phi behaviour of soil. The cohesion ranges from 5kPa to 10kPa and Phi ranges from 27 deg, to 30 deg.. But if i see according to SPT 'N' the DST results vary too much. For example in refusal N>100 also the DST shows a C- Phi of 10kPa and 30 deg.
And at some locations the Soil is in borderline classification of CLAY having low plasticity (CL) the undrained triaxial tests (UUT) had been conducted. The results were 55kPa (C) and 11 deg. (phi).

The in-situ permeability tests in
CL shows 5.57 x 10^-5 cm/s
ML-CL shows 4.125 x 10^-5 cm/s

So based on the permeability values how will be able to decide the behaviour is drained or undrained, So i can rule out the undrained tests and consider the CL layer drained parameters.

The foundation type is Pile foundation.
Ground water table is at 40m below Ground level.

Thanks your thoughts and advices.

RE: Fine grained soil Behaviour based on permeability

I think this blog may provide some help. Link

RE: Fine grained soil Behaviour based on permeability

Your in-situ permeabilities are relatively low, or moderate to be accurate. See info below.



Also the quote:

Quote:

- Dikes without any impermeable clay core may be built from soils having a coefficient of permeability less than
K = 1 x 10-4 m/s;
- Pond bottoms may be built into soils having a coefficient of permeability less than K = 5 x 10-6 m/s.

RE: Fine grained soil Behaviour based on permeability

Based on your description you have 40 m of soil before the groundwater table and the foundation is piles. I would assume you have 40 m of drained soils before having to check both the drained and undrained foundation soils.

Are you considering end bearing or friction fitting the piles?

RE: Fine grained soil Behaviour based on permeability

(OP)
Thank you retired13 for the references.

Geoenvguy:

Considering mostly the skin friction only, as end bearing have many issues like base cleaning and all.

RE: Fine grained soil Behaviour based on permeability

How long are the piles?

RE: Fine grained soil Behaviour based on permeability

(OP)
The piles were 29m length as preliminary analysis.

RE: Fine grained soil Behaviour based on permeability

So for 29m piles with a water table at 40m, how much excess pore water pressure will be generated during loading

RE: Fine grained soil Behaviour based on permeability

(OP)
to be very specific, The client want to have a option for recharge wells in that urban area for recharging the GWT. So if the GWT rises then the soil will get saturate. SO i may need to think of analyzing with undrained analysis. If they rule out the option of raising the GWT, then the soil is partially saturated and if i conduct the tests at natural moisture content (Direct shear tests, UU triaxial tests) i will get a apparent cohesion due to the silty dominance and low saturation. Correct me if i am wrong.

So what is your view on following which analysis (drained or Undrained) ?

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! Already a Member? Login


Resources

White Paper - PLM and ERP: Their Respective Roles in Modern Manufacturing
Leading manufacturers are aligning their people, processes, and tools from initial product ideation through to field service. They do so by providing access to product and enterprise data in the context of each person’s domain expertise. However, it can be complicated and costly to unite engineering with the factory and supply chain. Download Now
White Paper - Medical Device Design Control
Medical device product development is a highly integrated and regulated process. Implementation of a requirements tracking solution requires attention to a variety of nuanced topics. When presented with the task of tracking the many concept relationships in a project of this type, the initial software solution of choice tends to be a two-dimensional text systems. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close