Geo Struct Sparks LLC

When Mononobe-Okabe Equation Doesn't Work

Guestbook

Post a Comment

Oops!

Oops, you forgot something.

Oops!

The words you entered did not match the given text. Please try again.

Already a member? Sign In

8 Comments

Reply Michael Joseph Kappel
10:31 AM on September 25, 2012 
This is a very informative website. I was looking for stuff related to my project when I found it. It is not related but check out my website http://Geotrackable.org
Reply geostructsparks
7:20 AM on December 16, 2011 
How would your results differ for a multiple tieback soldier pile wall, with regards to pressure distribution and computing the static active pressure?
[/kevin]

Either WASP or Mononobe-Okabe equation are only for a theoretical soil wedge with no reinforcement. As you are aware, even conventional static tied back wall design involves highly simplified "theoretical" (more like SWAG) distributions of pressure, e.g. back-of-napkin drawings by Terzaghi, and so on. Unless there are finite element or scale model studies in the literature out there, there is no single accepted way to add seismic pressures to a retaining wall. I believe the main approach is to take the same approach as for static walls but increase the active pressure by changing Ka to Kae.

Federal Highway Administration for "restrained" walls (tied back retaining walls, pile-supported abutments and the like, due to the stiffness of the lateral support of the walls), requires that when you consider seismic pressure of one of these, you increase the Kh from 1/2 of the peak ground acceleration for a retaining system free to translate, to 1.5x peak ground acceleration (See Design Examples, US 395 at Plumb Lane). I have read the original commentary that spawned this idea, and while the authors suggested increased Kae by a factor of 3 , that is much less drastic that increasing the input horizontal acceleration by a factor of 3 as adopted by FHWA. The original commentary didn't provide a lot of justification for why this is accurate. For walls with stiff battered pile foundations, this conservatism may make sense; for tiebacks or MSE where the loads are tied back into the material that is providing the inertial load, this seems highly conservative.

(Sorry for the late response, I thought my site notified me by e-mail when comments were added)
Jonathan
Reply usnikkijamesl8
7:16 PM on June 16, 2011 
Awesome webpage from Carisa Heuer
Reply kevin
9:15 PM on April 29, 2011 
Jonathan
How would your results differ for a multiple tieback soldier pile wall, with regards to pressure distribution and computing the static active pressure?
Reply Dylan
5:40 PM on September 9, 2009 
ETA is one month or less!
Reply Eddy
4:34 PM on September 9, 2009 
What's the E.T.A. on the software? I have no pressing need but would love to see what you're up to.
Reply Matthew Behling, PE, MBA
7:39 PM on September 8, 2009 
Sweet, it's always exciting to learn and utilize a more effective and appropriate methodology for design. Looking forward to seeing the software.
Reply Dylan
12:16 AM on September 7, 2009 
We're on linkdin