×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

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!

*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

Infiltration Systems near Moisture Sensitive Structure Bearing Soils
2

Infiltration Systems near Moisture Sensitive Structure Bearing Soils

Infiltration Systems near Moisture Sensitive Structure Bearing Soils

(OP)
Here is an interesting topic. Where can water be infiltrated into the building load bearing moisture sensitive soils?

My thought is that the load extends at a 1:1 (+ or - with soil type) from the bottom of the footing, so not a great idea to introduce water within this area, until you get to a certain depth, as a function of some % load. And even then, still risky.

Interested if anyone else has some ideas when the site does not have much room for a required infiltration system?

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

Depending on the type of sensitive soils, a cut-off wall may be considered. Either dig a deep trench between the building an infiltration system and fill it with concrete or install sheeting.

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

The design strength of all soils is based on saturated conditions. The state of practice for unsaturated strength is not quite ready for prime time.

you are implying that if the soil gets wet something bad will happen. Please explain your failure mode?

If the soil is compacted below the critical void ratio (or resides that way in the natural state), in what way will the design strength or compressibility change when it gets wet?

'Cause, we'd have to really worry about our embankment dams!

f-d

ípapß gordo ainÆt no madre flaca!

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

(OP)
Good points, if the soil cannot densify, and has the overburden to resist expansion, that would help. I would be concerned about collapsible soil at depths that were not overexcavated and reprocessed, or (to relate to dam terms) 'piping' vertically into a non-natural open graded soil filter layer, especially with large volume infiltration systems with significant pressure heads. There are also many other variables such as utility trenches and the unknown subsurface soil that make me not a huge fan of the idea of saturating the soil beneath the structure. Part of the issue is the geotechnical design is completed well before the civil, which makes it difficult to go back and redesign.

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

Is this a real job? If so so details will help. Mother nature likes to bring water table levels to equal elevations in the long run.

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

Quote (Ocgeo)

Part of the issue is the geotechnical design is completed well before the civil, which makes it difficult to go back and redesign

If grading plans and FFEs are not finalized at the time of your geotechnical report, you should be requiring the engineers to provide those items when they are available so you can see if they impact your recommendations. Only then is your “design” (potentially) complete.

Im with OG. Is this just a theoretical question or does this pertain to a specific situation? Because they’re are too many variables in your opening post.

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

If you are talking about loess, and it has been demonstrated to be collapsible, be careful. A side issue is that the location of your infiltration facility may be rendered useless for future construction.

One thing that may work in your favor, however, is that loess may contain old small root holes that increase the vertical permeability and the wetted zone may have very steep sides, reducing the lateral effect. On the other hand, if there is an underlying low permeability formation, a groundwater mound that spreads out is likely to develop.

There are enough uncertainties that care is needed. I would resist a "required infiltration system" when building on loess. I have seen very serious building settlement problems caused by a water line leak some distance away.

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

Look at the experience with trees near buildings . . .

RE: Infiltration Systems near Moisture Sensitive Structure Bearing Soils

(OP)
That is a good point with loess (silts) and piping. That is a concern with the levees in Sacramento. The roots, active or dead, create a piping potential.

BigH, I also have had many issues with trees (I think the PTI has a lot of info on the soil moisture gain/loss potential in expansive soils). A good read on it also is simply explained in Forensic Geotechnical and Foundation Engineering, by Robert Day,

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

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. 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