×
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

Hi, can a clay layer with a Cu va

Hi, can a clay layer with a Cu va

Hi, can a clay layer with a Cu va

(OP)
Hi,
can a clay layer with a Cu value of 40kpa have a unit weight of 18kn/m2.
I have received a geotechnical investigation report with the above-mentioned condition.
When I checked with the Eurocode specification tables, it shows that,
1. if the Cu value is 40kpa, then the unit weight should be 15kn/m2.
2. otherwise if the unit weight is 18kn/m2, then the Cu value should be 80kpa.
and I cannot understand this correlation with Cu =40kpa and unit weight = 18kn/m2.
This soil layer is 2.0m to 4.2m depth from the ground level. The soil in this 2.2m thickness is a mixture of sensitive fine-grained and silty clay and clay.
The water table is at 1.45m below the ground level.

RE: Hi, can a clay layer with a Cu va

Geotech reports almost always are very conservative when "recommending" soil properties. It is very, very common for the geotech to recommend low cohesion, low friction angles, and high unit weight. This makes for a conservative design (and therefore less risk to the geotech). If the geotech's recommendations are just recommendations, then I use what I believe to be correct based on my experience and my review of the geotech report. However, be prepared to defend your soil properties to the reviewing engineer.

www.PeirceEngineering.com

RE: Hi, can a clay layer with a Cu va

Seems a confusing post. If you have an undisturbed sample and use it to measure undrained strength in the laboratory, you'd also have a sample to measure density in the laboratory. If these two laboratory tests give the data you suggest, then who cares about codes, correlations and the like? You did one better, you actually got the design values!

Good job!

f-d

ípapß gordo ainÆt no madre flaca!

RE: Hi, can a clay layer with a Cu va

Short answer yes it is possible to have an undrained shear strength of 40kpa and a unit weight of 18 kn/m3.

The easy way to check the geotechnical report is to look at the borehole logs and lab testing. The unit weight of the saturated clay is a function of the moisture content measured insitu. The undrained shear strength is a function of shear vane testing, triaxial testing or correlation from atterberg limits or SPT testing.

RE: Hi, can a clay layer with a Cu va

Agree with f-d, unit weight would be available if you have done a triax test.

When I have no testing in a Clay layer, other than Cu measured indirectly (i.e. SPT), i use the below. For your 40kPa you would be in the low to medium cat. A unit weight of 18-19 would be ok with me.

Fig 1 is from BS8002 - code of practice for foundations.

PEinc - a high unit weight would be unconservative for bearing capacity and pile end bearing in sand as higher confining pressures.



RE: Hi, can a clay layer with a Cu va

The values such as that, which are given in the AASHTO code are conservative default values that can be used if data about the on-site soils are not available. I would expect the Eurocode to be similar.

Rod Smith, P.E., The artist formerly known as HotRod10

RE: Hi, can a clay layer with a Cu va

EireChch, I agree with what you said about the heavy unit weight. I was thinking about non-gravity wall design, not bearing capacity for footings or for bearing piles. I should not have assumed that the original post was for a particular application.

www.PeirceEngineering.com

RE: Hi, can a clay layer with a Cu va

(OP)
Thank you for all your reactions.

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

Research Report - How Engineers are Using Remote Access
Remote access enables engineers to work from anywhere provided they have an internet connection. We surveyed our audience of engineers, designers and product managers to learn how they use remote access within their organizations. We wanted to know which industries have adopted remote access, which software they are using, and what features matter most. Download Now
eBook - Managing the Context of Product Complexity Using the Digital Twin
Keeping track of changes to complex products is difficult—think Aerospace & Defense equipment, new generations of commercial aircraft, and software-based automobiles. A new way to managing the digital context of the physical product is required and the answer is the Digital Twin. This ebook explores the opportunity available for Operations and Maintenance for the Digital Twin. Download Now
White Paper - Trends in Industrial Filtration
Substantial progress has been made in filtration technologies in recent years. New filter media materials, designs and processes have led to filters that are more efficient, reliable, compact and longer lasting. This white paper will discuss the various trends that are impacting operational responsibilities of MROs today and the resources that are available for staying up-to-date on the latest filtration solutions. 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