Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Levee Underseepage

Status
Not open for further replies.
nbr1

nbr1

Geotechnical
Joined
Feb 29, 2008
Messages
95
Location
US
Assuming a clay levee over an impervious top stratum overlying sand and fully loaded; is there a difference between the factor of safety against piping (FS=ic/i) at the levee toe (landside)
versus the factor of safety against uplift (landside toe)? Are these terms essentially the same phenomenon?
 
Sort by date Sort by votes
There was a discussion of this in a recent issue of ASDSO's monthly publication. I'm out of the office so, don't have the publication name or issue number handy.

In short, the factors of safety can be different since they represent different phenomenon. However, criteria are also usually quite different.

Personally, I use the method described in EM 1110-1-1913 by USACE for the design of levees. In that method the gradiant accross the impervious statum is compared to 0.5 for materials with a moist unit weight above 110 pcf.

Mike Lambert
 
Upvote 0 Downvote
Equation FS=ic/i will give safety factor with respect to critical exit gradient against boiling or heave. This failure mode is only applicable to the conditions where a levee is founded directly on cohesionless soil.

The safety factor against uplift is more applicable for your case. The confining layer(impervious stratum) may experience blowout if the seepage pressure in the pervious layer is higher than the overburden pressure of the confining layer .
 
Upvote 0 Downvote
I don't believe ic/i should be considered a factor of safety against piping. It's really about vertical seepage forces overcoming gravity, and Rilxouss is correct about it being for boiling or heave. Piping can occur from upward, downward, or sideways seepage. Some attempts have been made at finding the minimum gradients that can cause piping piping - John Schmertann, maybe 15-20 years ago, and somebody at Technical University of Delft working with clean fine sands. See if Google will find you anything. Very dependent on material types.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

nbr1
  • Locked
  • Question Question
Levee Stability - Riverside or Landside Excavation
Replies
5
Views
362
Erdbau
Erdbau
Arizona3106
  • Locked
  • Question Question
FEMA Levee Certification
Replies
6
Views
285
cvg
cvg
ntschwanz
  • Locked
  • Question Question
Reinforced Levee Question
Replies
10
Views
458
JML4TCM
JML4TCM
levee
  • Locked
  • Question Question
creating flood wall in levee using slope/w
Replies
3
Views
298
moe333
moe333

Part and Inventory Search

Sponsor

Back
Top